What evidence suggests that Mars once had more oxygen in its atmosphere than it does today?

According to a study released in the journal Nature, the Martian atmosphere may have been rich in oxygen 3.7 billion years ago. Such a fact would bode well for the continuing argument that the planet supported life at one time.
The study, authored by Bernard Wood of Oxford University, theorizes that the atmosphere of Mars might once have had plenty of oxygen after Wood and his colleagues compared meteorites from the planet to data on surface rocks collected by the Spirit rover. The samples, which share volcanic beginnings, were found to be geochemically different: the surface rocks were more oxygen-rich than the meteorites.
Spirit launched in 2004 with the Opportunity rover and operated until 2010. During that time it collected rock samples from Gusev Crater, a region of Mars estimated to be over 3.7 billion years old. Wood believes these ancient rocks may have come into contact with Mars’s oxygen atmosphere before experiencing subduction, when the rocks would have been recycled in the planet’s interior. The oxygen-rich rocks then reappeared via volcanic eruption some four billion years ago.
The meteor samples, alternatively, are being considered much “younger” than their surface counterparts. At anywhere between 180 million to 1.4 billion years old, these rocks likely came from deeper inside the Red Planet and thus had less contact with any oxygen that was in the atmosphere.
Although the theory is plausible, not everyone is in agreement that the samples are definitive proof that Mars obtained an atmosphere full of oxygen much earlier than Earth. Francis McCubbin of the University of New Mexico spoke with the BBC and stated that he did not reach Wood’s conclusions concerning the samples. He said that the oxidation of the surface could occur without the presence of oxygen gas.
However, he did agree with Wood’s conclusions that there are “substantial redox gradients with depth” on the planet. The process of redox (also known as reduction-oxidation) could potentially support certain types of life that use the reactions for energy and/or as a food source.
Yet Wood expects he is on to something. “As oxidation is what gives Mars its distinctive color, it is likely that the ‘red planet’ was wet, warm and rusty billions of years before Earth’s atmosphere became oxygen-rich,” he said.
In terms of how Mars would have beaten Earth to an oxygen heavy atmosphere, Wood explained that Mars’s lower gravity allowed for easier loss of hydrogen molecules during photolysis of existing water.

OXFORD, England, June 19 (UPI) -- A British scientist says new findings suggest Mars had an oxygen-rich atmosphere more than a billion years before Earth developed its own.
An examination of meteorites on Earth and rocks on Mars suggests oxygen was affecting the martian surface 4 billion years ago, at least 1,500 million years before oxygen built up in appreciable quantities in Earth's atmosphere, Bernard Wood of Oxford University said.
The evidence comes from a comparison of Martian meteorites that have crashed onto Earth and data from rocks examined by NASA's Spirit rover at a very ancient part of Mars containing rocks more than 3,700 million years old, researchers said.
Differences in composition can best be explained by an abundance of oxygen early in martian history, they said.
"The implication is that Mars had an oxygen-rich atmosphere at a time, about 4,000 million years ago, well before the rise of atmospheric oxygen on Earth around 2,500 million years ago," Wood told the Irish Times.
"As oxidation is what gives Mars its distinctive color, it is likely that the 'red planet' was wet, warm and rusty billions of years before Earth's atmosphere became oxygen rich," he said.

A recent study by researchers at Oxford University has shown that the planet Mars may hav had an oxygen-rich atmosphere 4 billion years ago.
Using meteorites identified as coming from Mars, as well as data from Mars rover Spirit, researchers found that rocks currently found on the surface of Mars have much more nickel than the meteorites. This suggests, researchers say, that the early Martian surface was full of oxygen. The findings have been published in the journal Nature.
"What we have shown is that both meteorites and surface volcanic rocks are consistent with similar origins in the deep interior of Mars but that the surface rocks come from a more oxygen-rich environment, probably caused by recycling of oxygen-rich materials into the interior," said Bernard Wood, a co-author of the study and a professor in Oxford University's Department of Earth Sciences. "This result is surprising because while the meteorites are geologically 'young', around 180 million to 1,400 million years old, the Spirit rover was analysing a very old part of Mars, more than 3,700 million years old."
Wood and his colleagues believe that the different compositions of the Martian material may be due to subduction, the process by which surface material is recycled into a planet's interior. The hypothesis is that Mars was very oxidized early in its history, and that subduction has brought early surface material to where Spirit found it, while the meteorites are younger Martian material from deeper within the planet.
"The implication is that Mars had an oxygen-rich atmosphere at a time, about 4000 million years ago, well before the rise of atmospheric oxygen on earth around 2500 million years ago," said Wood. "As oxidation is what gives Mars its distinctive colour it is likely that the 'red planet' was wet, warm, and rusty billions of years before Earth's atmosphere became oxygen rich."

Early Mars atmosphere 'oxygen-rich' before Earth's
- 19 June 2013
- From the section Science & Environment
Mars' atmosphere could have been rich in oxygen four billion years ago - well before Earth's air became augmented with the gas.
That is the suggestion put forward by the author of a study in Nature journal, which outlines an explanation for differences between Mars meteorites and rocks examined by a robot rover.
Dr Bernard Wood said the idea fits with the picture of a planet that was once warm, wet and habitable.
But other scientists were sceptical.
While the rise of atmospheric oxygen on Earth 2.5 billion years ago was probably mediated by life, Martian oxygen could have been produced through the chemical "splitting" of water.
Prof Wood and his colleagues from Oxford University looked at the chemical composition of Martian meteorites found on Earth and data from Nasa's Spirit rover, which examined surface rocks at Gusev Crater on Mars.
Both are igneous rocks (of volcanic origin), but they show major geochemical differences. For example, the Gusev Crater rocks are five times richer in nickel than the meteorites.
This had posed something of a puzzle, casting doubt on whether the meteorites were typical volcanic products of the Red Planet.
Young and old
"What we have shown is that both meteorites and surface volcanic rocks are consistent with similar origins in the deep interior of Mars, but that the surface rocks come from a more oxygen-rich environment, probably caused by recycling of oxygen-rich materials into the interior," Prof Wood explained.
"This result is surprising because while the meteorites are geologically 'young', around 180 million to 1.4 billion years old, the Spirit rover was analysing a very old part of Mars, more than 3.7 billion years old."
Whilst the researchers conceded that large regional variations in the geological composition of Mars could not be ruled out, they argue in their paper that these differences arose via subduction - in which rocks are recycled in the planet's interior.
Dr Wood, James Tuff and Jon Wade from Oxford propose that the Martian surface became "oxidised" early in its history, and that these surface rocks were drawn into the shallow interior and recycled back to the surface during volcanic eruptions around four billion years ago.
The meteorites, by contrast, are much younger volcanic rocks that emerged from deeper within Mars and so were less influenced by this process.

Although material can become oxidised in the presence of free oxygen gas - it is not essential for oxidation reactions to occur.
But Dr Francis McCubbin, from the University of New Mexico, who was not involved with the Nature study, told BBC News: "I did not reach the conclusion that their results imply an early oxygen-rich atmosphere on Mars, only that the upper mantle was more oxidised than the deep interior, which does not actually require any oxygen gas to accomplish."
"I agree with the overarching conclusions of this work that there are substantial redox gradients with depth on Mars, and this could be potentially very important for Mars' habitability because some organisms can take advantage of redox (reduction-oxidation) reactions and use them as an energy/food source.
He added: "Although not implicitly stated, the early oxidized magmatism would also favour the production of water, another ingredient that is key to habitability."
On alternative possibilities to atmospheric oxygen, Prof Wood told BBC News: "One is that Mars was an initially oxidised planet - that's pretty unlikely. There aren't any meteorites or other bodies in the Solar System that show this high state of oxidation.
"You don't need a lot of oxygen to cause this - you don't need to be at 20% concentration. It would depend on temperature and how much water was around. But you need free oxygen to do it.
"And the process didn't take place to any great extent on Earth at that time - which is interesting."
Prof Wood explained that, as oxidation was what gave Mars its distinctive colour, it is likely that the planet was "warm, wet and rusty" billions of years before Earth's atmosphere became oxygen-rich.
He added: "The principal way we would expect to get oxygen is through photolysis of water - water vapour in Mars' atmosphere interacting with radiation from the Sun breaks down to form hydrogen and oxygen.
"Most of that hydrogen and oxygen recombines back to water. But a small fraction of the hydrogen is energetic enough to escape from the planet. A small amount of hydrogen is lost leaving an oxygen excess.
"But the gravity on Mars is one third of that on Earth, so hydrogen would be lost more easily. So the oxygen build-up could be enhanced on Mars relative to Earth."
Paul.Rincon-INTERNET@bbc.co.uk and follow me on Twitter

New chemical science findings from NASA’s Mars rover Curiosity indicate that ancient Mars likely had a higher abundance of molecular oxygen in its atmosphere compared to the present day and was thus more hospitable to life forms, if they ever existed.
Thus the Red Planet was much more Earth-like and potentially habitable billions of years ago compared to the cold, barren place we see today.
Manganese-oxide minerals require abundant water and strongly oxidizing conditions to form.
“Researchers found high levels of manganese oxides by using a laser-firing instrument on the rover. This hint of more oxygen in Mars’ early atmosphere adds to other Curiosity findings — such as evidence about ancient lakes — revealing how Earth-like our neighboring planet once was,” NASA reported.
The newly announced results stem from results obtained from the rovers mast mounted ChemCam or Chemistry and Camera laser firing instrument. ChemCam operates by firing laser pulses and then observes the spectrum of resulting flashes of plasma to assess targets’ chemical makeup.
“The only ways on Earth that we know how to make these manganese materials involve atmospheric oxygen or microbes,” said Nina Lanza, a planetary scientist at Los Alamos National Laboratory in New Mexico, in a statement.
“Now we’re seeing manganese oxides on Mars, and we’re wondering how the heck these could have formed?”
The discovery is being published in a new paper in the American Geophysical Union’s Geophysical Research Letters. Lanza is the lead author.
The manganese oxides were found by ChemCam in mineral veins investigated at “Windjana” and are part of geologic timeline being assembled from Curiosity’s research expedition across of the floor of the Gale Crater landing site.
Scientists have been able to link the new finding of a higher oxygen level to a time when groundwater was present inside Gale Crater.
“These high manganese materials can’t form without lots of liquid water and strongly oxidizing conditions,” says Lanza.
“Here on Earth, we had lots of water but no widespread deposits of manganese oxides until after the oxygen levels in our atmosphere rose.”
The high-manganese materials were found in mineral-filled cracks in sandstones in the “Kimberley” region of the crater.
High concentrations of manganese oxide minerals in Earth’s ancient past correspond to a major shift in our atmosphere’s composition from low to high oxygen atmospheric concentrations. Thus its reasonable to suggest the same thing happened on ancient Mars.
As part of the investigation, Curiosity also conducted a drill campaign at Windjana, her 3rd of the mission.

During the same relative time period, other clues indicate more oxygen was present in the atmosphere thanfound currently
Space news (planetary science: Martian rocks containing manganese oxide minerals; indicating a wetter surface with more atmospheric oxygen than presently found on Mars) – Mars (the Red Planet), 154 million miles (249 kilometers) from Sol, or 141 million miles (228 million kilometers) from Earth, on average –
NASA’s Curiosity Mars rover has found rocks at a place called Windjana containing manganese oxide minerals according to reports from planetary scientists studying samples from the region. On Earth rocks of this type formed during the distant past in the presence of abundant water and atmospheric oxygen. This news added to previous reports of ancient lakes and other groundwater sources during Mar’s pastpoints to a wetter environment in the study region Gale Crater during this time.
Planetary scientists used the laser-firing instrument on the Curiosity Mars rover to detect high levels of manganese-oxide in mineral veins found at Windjana. “The only ways on Earth that we know how to make these manganese materials involve atmospheric oxygen or microbes,” said Nina Lanza, a planetary scientist at Los Alamos National Laboratory in New Mexico. “Now we’re seeing manganese oxides on Mars, and we’re wondering how the heck these could have formed?”
Planetary scientists are looking at other processes that could create the manganese-oxide they found in rocks in Mar’s Gale Crater region. Possible culprits at this point include microbes, but even optimistic planetary scientists are finding little fan fair accompanyingtheir ideas. Lanza said, “These high manganese materials can’t form without lots of liquid water and strongly oxidizing conditions. Here on Earth, we had lots of water but no widespread deposits of manganese oxides until after the oxygen levels in our atmosphere rose.”
Geologists have found high concentrations of manganese oxide minerals is an important marker of a major shift in Earth’s atmospheric composition, from relatively low oxygen levels during the distant past, to the oxygen-rich environment we live in today. Planetary scientists studying the rocks they found in Gale Crater suggest the presence of these materials indicates oxygen levels on Mars rose also, before declining to the present low levels detected. The question is how was Mar’s oxygen-rich atmosphere formed?
“One potential way that oxygen could have gotten into the Martian atmosphere is from the breakdown of water when Mars was losing its magnetic field,” said Lanza.

Mars is blanketed by a thin, mostly carbon dioxide atmosphere -- one that is far too thin to keep water from freezing or quickly evaporating. However, geological evidence has led scientists to conclude that ancient Mars was once a warmer, wetter place than it is today. To produce a more temperate climate, several researchers have suggested that the planet was once shrouded in a much thicker carbon dioxide atmosphere. For decades that left the question, "Where did all the carbon go?"
The solar wind stripped away much of Mars' ancient atmosphere and is still removing tons of it every day. But scientists have been puzzled by why they haven't found more carbon -- in the form of carbonate -- captured into Martian rocks. They have also sought to explain the ratio of heavier and lighter carbons in the modern Martian atmosphere.
Now a team of scientists from the California Institute of Technology and NASA's Jet Propulsion Laboratory, both in Pasadena, offer an explanation of the "missing" carbon, in a paper published today by the journal Nature Communications.
They suggest that 3.8 billion years ago, Mars might have had a moderately dense atmosphere. Such an atmosphere -- with a surface pressure equal to or less than that found on Earth -- could have evolved into the current thin one, not only minus the "missing" carbon problem, but also in a way consistent with the observed ratio of carbon-13 to carbon-12, which differ only by how many neutrons are in each nucleus.
"Our paper shows that transitioning from a moderately dense atmosphere to the current thin one is entirely possible," says Caltech postdoctoral fellow Renyu Hu, the lead author. "It is exciting that what we know about the Martian atmosphere can now be pieced together into a consistent picture of its evolution -- and this does not require a massive undetected carbon reservoir."
When considering how the early Martian atmosphere might have transitioned to its current state, there are two possible mechanisms for the removal of the excess carbon dioxide. Either the carbon dioxide was incorporated into minerals in rocks called carbonates or it was lost to space.
An August 2015 study used data from several Mars-orbiting spacecraft to inventory carbonates, showing there are nowhere near enough in the upper half mile (one kilometer) or the crust to contain the missing carbon from a thick early atmosphere during a time when networks of ancient river channels were active, about 3.8 billion years ago.
The escaped-to-space scenario has also been problematic.

“It’s thought that at this time in Mars’ history, water was much more abundant. Yet without a protective magnetic field to shield the surface, ionizing radiation started splitting water molecules into hydrogen and oxygen. Because of Mars’ relatively low gravity, the planet wasn’t able to hold onto the very light hydrogen atoms, but the heavier oxygen atoms remained behind. Much of this oxygen went into rocks, leading to the rusty red dust that covers the surface today. While Mars’ famous red iron oxides require only a mildly oxidizing environment to form, manganese oxides require a strongly oxidizing environment, more so than previously known for Mars.“
Lanza added, “It’s hard to confirm whether this scenario for Martian atmospheric oxygen actually occurred. But it’s important to note that this idea represents a departure in our understanding for how planetary atmospheres might become oxygenated. Abundant atmospheric oxygen has been treated as a so-called biosignature or a sign of extant life, but this process does not require life.“
The Curiosity rover has been investigating Gale Crater for around four years and recent evidence supports the possibilityconditions needed to form these deposits were present in other locations. The concentrations of manganese oxide discovered were found in mineral-filled cracks in sandstones in a region of the crater called “Kimberley”. NASA’s Opportunity rover has been exploring the surface of the planet since 2004 and recently reported similar high manganese deposits in a region thousands of miles away. Supporting the idea environments required to form similar deposits could be found well beyond Gale Crater.
What’s next for Curiosity?
NASA’s Curiosity rover’s currently collecting drilled rock powder from the 14th drill site called the Murray formation on the lower part of Mount Sharp. Plans call for NASA’s mobile laboratory to head uphill towards new destinations as part of a two-year mission extension starting near the beginning of October.
The rover will go forward about a-mile-and-a-half (two-and-a-half-kilometers) to a ridge capped with material rich in the iron-oxide mineral hematite first identified by observations made with NASA’s Mars Reconnaissance Orbiter. Just beyond this area, there’s also a region with clay-rich bedrock planetary scientists want to have a closer look.

It may be time to call off the search for Mars' missing carbon.
Mars' carbon-rich atmosphere was once thick enough to raise the planet's surface temperature and allow entire oceans of liquid water to form there — a drastic change from the cold desert it is today. This metamorphosis of the Red Planet has put scientists on the hunt for a left-over "carbon reservoir" in the planet's dirt and soil. So far, the has come up empty.
But new research has concluded that "a large 'missing' carbon reservoir is unnecessary" to explain the planet's watery past, and that the Martian air wasn't exceptionally dense billions of years ago. . [Amazing Photos from Mars' Curiosity Rover]
Like any planetary system, Mars' atmosphere is intimately linked with conditions on the planet's surface. The new work Learning just how thick the atmosphere was long ago, and how quickly it changed, could help answer questions about Mars' evolution, and as well as its potential for supporting life
The disappearing Martian atmosphere
There's no doubt that ancient Mars was different than the Red Planet seen today. Humanity seems to have missed a heyday in the Red Planet's history, when the surface was spotted with lakes and oceans, temperatures were warmer, and the atmosphere was thicker.
Then again, the atmosphere would likely have consisted mostly of carbon dioxide, so it's not as though humans could have survived there unaided. But it's very possible that other forms of life found ancient Mars quite homey. (The very salty liquid water recently discovered on the surface of Mars suggests that the planet could still be hospitable to some life-forms.)
Where did Mars' thick atmosphere disappear to? Without a protective magnetic field around it, like Earth, Mars is exposed to the harsh environment of space. Energetic particles of light from the sun can chemically react with particles in the atmosphere and eject them from the planet. NASA's MAVEN orbiter recently showed that solar winds may have swept away a significant portion of Mars' atmosphere.
Freed carbon atoms could also have been absorbed into the Martian dirt and soil, creating what are called "carbonates" — a sort of residue left over by the now-gone atmosphere.
But tests of the Martian soil show very low levels of carbonates — the "carbon reservoir" has not been found.

Even though Mars is currently too cold and has too little pressure to prevent water from freezing, the planet had liquid water on its surface in the distant past. That could happen if the ancient Martian atmosphere, thicker than its present-day counterpart, had enough greenhouse gasses to keep the planet warm and the water liquid. So over the past decades of our observations and robotic visitations of Mars, researchers have been looking for evidence for Mars' past carbon dioxide levels.
The evidence we've gathered indicates there was some CO2 present but not nearly enough to keep water liquid, especially given that the early Sun was less active than it is at present. So far, these estimates contained large uncertainties, so it remained possible that there was enough carbon in the atmosphere to allow the ancient water to flow.
A team of researchers has created a new estimate of Mars' ancient carbon levels using data collected by the Curiosity rover. They've also concluded that there was nowhere near enough CO2 to warm the planet to the point where water on the surface would remain liquid.
During its trip towards Aeolis Mons (the peak at the center of the Gale crater), Curiosity came upon what looked to be the remains of an ancient lake. This was a region of about 70 meters with mudstones, siltstones, and sandstones left behind by ancient water, somewhere between 3.8 and 3.1 billion years ago. The rover analyzed these materials as it passed, but there were no carbonate minerals, which would have made assessing past carbon levels easier. However, certain clays could provide a way to estimate the ancient carbon concentration.
When these clays formed, CO2 would have dissolved into their structure. While we can't measure them, we can infer their presence indirectly, as dissolved carbon limits the solubility of iron-bearing olivine. The amount of this olivine in the clays puts a limit on the amount of CO2 that could be in the water that the clays formed in.
This technique is also used to estimate Earth’s early atmosphere, but here it’s actually less reliable because the presence of life contaminates the process. The Martian rocks have been comparatively undisturbed, making them prime targets for science. “In many ways, deriving [CO2] estimates from Gale Crater sedimentary rocks is more straightforward than doing so in their terrestrial equivalents,” the authors write in their paper.

"It's very hard proving that something has been lost," Yuk Yung, a professor of planetary science at the California Institute of Technology and an author on the new research paper, told Space.com.
He said the situation with Mars' atmosphere resembled asking a question about a bucket of water.
"Suppose I have a bucket of water, and there's only 1 inch [2.54 centimeters] of water in it," Yung said. "Suppose I tell you that some time ago, the bucket was full. Now, most of the water is gone. If I ask you for proof that it was full [that will be difficult]. It's very hard to prove something that's not there."
But Yung and his colleagues finally have their hands on concrete evidence about the thickness of the ancient, missing Martian atmosphere, and how quickly it escaped.
More than 10 years ago, Yung and his then-graduate student David Kass studied meteorites that had fallen to Earth, but which had originated on Mars. The researchers tested the meteorites, and looked for two kinds of carbon that are found in the Martian atmosphere: carbon 12 (called 12C) and carbon 13 (13C).
Carbon 13 is the heavier of these two siblings (it carries one extra neutron). Yung said the heavier carbon sinks lower down in the atmosphere, and if the atmosphere were poured out, like water from a bucket, more carbon 12 would escape than carbon 13. The ratio of these two types of carbon therefore tells a story about how quickly the Martian atmosphere was "poured off": If the atmosphere contained a 50/50 split of carbon 12 and carbon 13 at a point 3 billion years ago, then the carbon 13 would now make up a larger portion of the pie.
The meteorites provide the ratio of carbon 13 to carbon 12 that would have been present in ancient Mars. Measuring that same ratio for modern-day Mars actually proved more difficult; Yung and Kass initially tried to use data from NASA's Viking landers, but said the result was too uncertain.
Kass graduated before they could complete the project, but Renyu Hu, a post doctoral researcher now working with Yung at Caltech, picked up where they left off. It was the suite of science instruments on board the Curiosity rover that finally provided the measurement they needed.
"This is a very difficult measurement," Yung said.

Because various processes can change the relative amounts of carbon-13 to carbon-12 isotopes in the atmosphere, "we can use these measurements of the ratio at different points in time as a fingerprint to infer exactly what happened to the Martian atmosphere in the past," says Hu. The first constraint is set by measurements of the ratio in meteorites that contain gases released volcanically from deep inside Mars, providing insight into the starting isotopic ratio of the original Martian atmosphere. The modern ratio comes from measurements by the SAM (Sample Analysis at Mars) instrument on NASA's Curiosity rover.
One way carbon dioxide escapes to space from Mars' atmosphere is called sputtering, which involves interactions between the solar wind and the upper atmosphere. NASA's MAVEN (Mars Atmosphere and Volatile Evolution) mission has yielded recent results indicating that about a quarter pound (about 100 grams) of particles every second are stripped from today's Martian atmosphere via this process, likely the main driver of atmospheric loss. Sputtering slightly favors loss of carbon-12, compared to carbon-13, but this effect is small. The Curiosity measurement shows that today's Martian atmosphere is far more enriched in carbon-13 -- in proportion to carbon-12 -- than it should be as a result of sputtering alone, so a different process must also be at work.
Hu and his co-authors identify a mechanism that could have significantly contributed to the carbon-13 enrichment. The process begins with ultraviolet (UV) light from the sun striking a molecule of carbon dioxide in the upper atmosphere, splitting it into carbon monoxide and oxygen. Then, UV light hits the carbon monoxide and splits it into carbon and oxygen. Some carbon atoms produced this way have enough energy to escape from the atmosphere, and the new study shows that carbon-12 is far more likely to escape than carbon-13.
Modeling the long-term effects of this "ultraviolet photodissociation" mechanism, the researchers found that a small amount of escape by this process leaves a large fingerprint in the carbon isotopic ratio. That, in turn, allowed them to calculate that the atmosphere 3.8 billion years ago might have had a surface pressure a bit less thick than Earth's atmosphere today.
"This solves a long-standing paradox," said Bethany Ehlmann of Caltech and JPL, a co-author of both today's publication and the August one about carbonates.

in the magazine Earth and Planetary Science Letters Scientists describe a model developed for the evolution of the Martian atmosphere that combines the high temperatures after the planet formed with the formation of the first oceans and atmosphere.
It shows that Water vapor is concentrated in the lower atmosphereThe upper layers remained dry. A similar situation is currently taking place on Earth, where there is a large part of it Moisture condenses as clouds in the troposphereat altitudes of up to 20 km.
Molecular hydrogen that did not combine with oxygen to form a water molecule, to the upper atmosphere of Mars, where it escaped into space. This assumption allows for Direct link between this model and Curiosity’s measurements.
The researchers responsible for the study believe they made Example of a previously overlooked chapter in Martian history. It may be important to understand to note that Long ago, the atmosphere of Mars was definitely denser than it is today (about 1,000 times) It is mainly composed of molecules containing two hydrogen atoms.
This is a major discovery because it is known Hydrogen in this form is a strong greenhouse gas in a dense environment. In an atmosphere of this formation, there will be a greenhouse effect that will be able to Preserving liquid water for millions of years.
It also turned out to be interesting deuterium ratio (heavy hydrogen isotope) to hydrogen in various Martian samples, including Meteorites and elements studied by Curiosity. Mars meteorites are Igneous rocks from the mantle of Marsthat arose at a time when Mars was still characterized by volcanic activity.
Water melted in fiery samples from Mars’ mantle It shows a ratio of deuterium to hydrogen similar to a measurement made in Earth’s oceans. This proves it Water on both planets came from the same source in the early solar system.
Curiosity measured the ratio of deuterium to hydrogen in the 3-billion-year-old clay And I found out that there was Three times larger than the Earth’s oceans. The only process that may be responsible for this level of deuterium concentration is Loss of the lighter hydrogen isotope in space.
The model shows that if The atmosphere of Mars contained diatomic hydrogen at the time of the planet’s formation, surface water would naturally be enriched in deuterium by a factor 2-3 times greater than the interior of Mars. This, in turn, confirms the observations of scientists. Deuterium is more likely to form water than molecular hydrogenwhich traps ordinary hydrogen and escapes from the upper atmosphere.

Although this is the period in Mars’s history when erosion rates were comparatively high, they are still far below those typical on Earth (Golombek et al., 2006), which is consistent with the preservation of large ancient features on the planet’s surface (Carr & Head, 2010). And although hydrated minerals are found on Noachian surfaces, so are unaltered basalts such as olivine and pyroxene. Because the timescale to completely weather surface olivine is less than several million years (Olsen & Rimstidt, 2007), this implies that on average the Noachian global hydrological cycle on Mars was less intense than that on Earth.
The global mean surface pressure on Mars today is ~6.1 hPa, which is very close to the triple point pressure of water. If liquid water flowed during the Noachian, then the surface pressure must have been higher than the triple point to prevent rapid boil off. How much higher is difficult to ascertain, but a plausible estimate is ~100 hPa (McKay, 2004). If greenhouse warming played a role, as many researchers believe, then a substantially thicker CO2 atmosphere is implied. Support for a much thicker early atmosphere comes from isotopic data (Table 2). H, N, Ar, and Xe are all isotopically heavy compared to those on Earth, which is best explained by the preferential escape of the lighter isotopes (Haberle et al., 2017). Escape can occur thermally (e.g., Jeans escape) or nonthermally (e.g., sputtering or dissociative recombination). Present measured escape rates by the MAVEN spacecraft could account for the loss of 800 hPa of CO2 over the history of the planet (Jakosky et al., 2018). Thus, it is highly likely that the surface pressure during the Noachian was much higher than it is today. How much higher is not known.
Table 2. Key Isotope Ratios Indicating Loss of an Early Atmosphere on Mars
Mass fractionating nonthermal escape
Early loss of 36Ar (impact erosion?)
Very early loss of 132Xe (hydrodynamic escape?)

"We are now able to quantify what people previously could only estimate."
Comparing these values, Yung said it appears that the pressure in the atmosphere wasn't as high as some models predict. Specifically, it's less than 1 bar (which is about the pressure of Earth's atmosphere at sea level), while there are planetary models that estimate higher values.
This finding is significant because it changes the amount of carbonites scientists should expect to find in the Martian soil, and "does not require a massive undetected carbon reservoir," Hu said in a news release from NASA's Jet Propulsion Laboratory.
Yung said the measurement is new, but it is in agreement with the recent findings from MAVEN, showing how the Martian atmosphere may have been swept away by solar winds.
Yung said work still needs to be done to put the new results into detailed models of Mars' evolution, so scientists can discover what the findings reveal about Mars' history. Was the warm, wet period in the planet's lifetime a brief window? What would such a finding indicate for the possibility of life forming on the Martian surface? Working the new results into established models may reveal exciting new details.
"This solves a long-standing paradox," said Bethany Ehlmann, a researcher at Caltech and JPL, and co-author on the new research paper.
"The supposed very thick atmosphere [of ancient Mars] seemed to imply that you needed this big surface carbon reservoir," Ehlmann said, but the new paper shows that known processes are enough to explain the "missing" carbonates, and will allow scientists find "an evolutionary scenario for Mars that makes sense."

Despite this, about 3.8 billion years ago, there was a denser atmosphere, higher temperature, and vast amounts of liquid water flowed on the surface, including large oceans.
It has been estimated that the primordial oceans on Mars would have covered between 36% and 75% of the planet. On November 22, 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior. Analysis of Martian sandstones, using data obtained from orbital spectrometry, suggests that the waters that previously existed on the surface of Mars would have had too high a salinity to support most Earth-like life. Tosca et al. found that the Martian water in the locations they studied all had water activity, aw ≤ 0.78 to 0.86—a level fatal to most Terrestrial life. Haloarchaea, however, are able to live in hypersaline solutions, up to the saturation point.
In June 2000, possible evidence for current liquid water flowing at the surface of Mars was discovered in the form of flood-like gullies. Additional similar images were published in 2006, taken by the Mars Global Surveyor, that suggested that water occasionally flows on the surface of Mars. The images did not actually show flowing water. Rather, they showed changes in steep crater walls and sediment deposits, providing the strongest evidence yet that water coursed through them as recently as several years ago.
There is disagreement in the scientific community as to whether or not the recent gully streaks were formed by liquid water. Some suggest the flows were merely dry sand flows. Others suggest it may be liquid brine near the surface, but the exact source of the water and the mechanism behind its motion are not understood.
Silica[edit | hide | edit source]
In May 2007, the Spirit rover disturbed a patch of ground with its inoperative wheel, uncovering an area extremely rich in silica (90%). The feature is reminiscent of the effect of hot spring water or steam coming into contact with volcanic rocks. Scientists consider this as evidence of a past environment that may have been favorable for microbial life, and theorize that one possible origin for the silica may have been produced by the interaction of soil with acid vapors produced by volcanic activity in the presence of water.

This is the process wherein the water vapor of Mars would have broken down into its component elements through the interaction of the atmosphere with radiation from the Sun.
“So the oxygen build-up could be enhanced on Mars relative to Earth,” he said.

- Robert M. HaberleRobert M. HaberleNASA Ames Research Center - Space Science and Astrobiology Division
The climate of Mars has evolved over time. Early in its history, between 3.7 and 4.1 billion years ago, the climate was warmer and wetter and the atmosphere thicker than it is today. Erosion rates were higher than today, and liquid water flowed on the planet’s surface, carving valley networks, filling lakes, creating deltas, and weathering rocks. This implies runoff and suggests rainfall and/or snowmelt. Oceans may have existed. Over time, the atmosphere thinned, erosion rates declined, water activity ceased, and cooler and drier conditions prevailed. Ice became the dominate form of surface water. Yet the climate continued to evolve, driven now by large variations in Mars’ orbit parameters. Beating in rhythm with these variations, surface ice has been repeatedly mobilized and moved around the planet, glaciers have advanced and retreated, dust storms and polar caps have come and gone, and the atmosphere has collapsed and re-inflated many times. The layered terrains that now characterize both polar regions are telltale signatures of this cyclical behavior and owe their existence to modulations of the seasonal cycles of dust, water, and CO2. Contrary to the early images from the Mariner flybys of the 1960s, Mars is and has been a dynamically active planet whose surface has been partly shaped through its interaction with a changing atmosphere and climate system.
- Planetary Atmospheres and Oceans
- Planetary Ionospheres and Magnetospheres
- Planetary Surfaces
- Planetary Chemistry and Cosmochemistry
Today Mars is cold and dry with a thin CO2 atmosphere. It is a dusty, desert planet with no stable liquid water on its surface. Yet spacecraft data suggest a different climate prevailed in the past. Images of fluvial features on its oldest surfaces, for example, suggest that very early in its history water flowed freely. Warmer and wetter conditions under a thicker greenhouse atmosphere are implied. Isotopic data and surface mineralogy support this view. Lakes and even oceans may have existed, powered perhaps by a sustained global hydrological cycle involving evaporation, rainfall, and runoff. This, however, has been theoretically difficult to demonstrate given the faint young Sun and limitations on the sources and sinks of plausible greenhouse gases.

The atmosphere of Mars may not have escaped into space billions of years ago, scientists say. Instead, the bulk of Mars' carbon dioxide gas could be locked inside Martian rocks.
Most of Mars' carbon dioxide vanished about 4 bildflion years ago, leaving a cold planet covered in a thin veneer of gas. But a new analysis of a Martian meteorite claims that some of the carbon dioxide disappeared into Mars itself, and not out into space as previous studies have suggested.
"This is the first direct evidence of how carbon dioxide is removed, trapped and stored on Mars," said Tim Tomkinson, lead study author and a geochemist at the University of Glasgow in the United Kingdom. "We can find out amazing things about Mars from the very small amount of sample that we have." [7 Biggest Mysteries of Mars]
Tomkinson and his colleagues probed the history of the Mars atmosphere by analyzing minerals in a tiny slice of the Lafayette meteorite, a Mars rock blasted toward Earth 11 million years ago. The Lafayette is one of several Martian meteorites called the Nakhlites, thought to have been ejected out of a vast volcanic plateau by a comet impact.
The meteorites are 1.3-billion-year-old basalt, a volcanic rock rich in the mineral olivine. Long before their space journey, water altered the rock, leaving behind microscopic fractures filled with clays and carbonates. Radiometric dating indicates these minerals formed some 625 million years ago. The research is detailed in the Oct. 22 edition of the journal Nature Communications.
Tomkinson's team discovered that Lafayette's siderite, an iron-rich carbonate mineral, formed through carbonation. (This is the same process proposed for carbon sequestration on Earth.) When water and carbon dioxide gas combine with olivine minerals in the basalt, the ensuing chemical reaction creates carbonate and silicate minerals, trapping the gas.
The results mean liquid water flowed on Mars within the last 700 million years, either from geothermal or hydrothermal heating, Tomkinson said. "This process could have been an even bigger player when Mars was thought to be a warmer and wetter planet," he added. "This process was still occurring when conditions were unfavorable for carbonation. It could potentially have been a much bigger mechanism when Mars had a thicker atmosphere 4 billion years ago," Tomkinson told SPACE.com.
NASA's Mars spacecraft and rovers have already found widespread carbonate deposits on the planet.

Researchers suggested that pressure from charged particles in the solar wind blew the lighter hydrogen molecules out of Mars' atmosphere, because the planet has no global magnetic field to protect it. Additionally, the water molecules Mars had in its atmosphere likely broke apart under the sun's ultraviolet light.
Past infrared observations with the W. M. Keck Observatory, the NASA Infrared Telescope Facility and the European Southern Observatory's Very Large Telescope showed that the Martian polar caps are highly enriched in deuterium, supporting the theory that deuterium remained behind. Mars' frozen water has a ratio of 1 hydrogen molecule to 400 deuterium molecules — about eight times greater than the ratio in Earth's oceans, which is 1 hydrogen molecule to 3,200 deuterium molecules, the 2015 research showed.
"Now we know that Mars water is much more enriched than terrestrial ocean water in the heavy form of water, the deuterated form," Michael Mumma, a senior scientist at NASA's Goddard Space Flight Center in Maryland, said in the 2015 video. "Immediately that permits us to estimate the amount of water Mars has lost since it was young."
In the ancient past, Mumma added, Mars had an ocean that covered about 20 percent of the planet's surface area — "a respectable ocean," he said. The body of water was about 5,000 feet (1,500 meters) deep, on average. Today, only 13 percent of that ancient ocean remains, locked in the polar ice caps.
In separate observations, the Mars Curiosity rover, located at Gale Crater near the Martian equator, found that conditions were wet in that region for about 1.5 billion years. That period of time, Mumma said, "is already much longer than the period of time needed for life to develop on Earth." The infrared telescope observations suggested that "Mars must have been wet for a period even longer," he added. [Building the James Webb Space Telescope]
The Webb telescope, which is designed for infrared observations, will follow up on the normal-water and heavy-water observations performed by the other observatories, NASA officials said in the statement. It will watch the normal-water-to-heavy-water ratio during different seasons, and at different times and locations.

A new NASA video shows what Mars may have been like long ago when it had a denser atmosphere and liquid water.
The concept is based on evidence that Mars was once very different.
"There are characteristic dendritic structured channels that, like on Earth, are consistent with surface erosion by water flows,” said Joseph Grebowsky of NASA's Goddard Space Flight Center
in Greenbelt, Maryland. “The interiors of some impact craters have basins suggesting crater lakes, with many showing connecting channels consistent with water flows into and out of the crater.”
He added that small impact craters have been removed with time and larger craters show signs of erosion by water more than 3.7 billion years ago, and sedimentary layering is seen on valley walls. Minerals are present on the surface that can only be produced in the presence of liquid water, Grebowsky said.
Estimates about the amount of water needed to explain these features have equated to possibly as much as a planet-wide layer one-half a kilometer (1,640 feet) deep or more, according to Grebowsky.
It's unknown if the habitable climate lasted long enough for life to emerge on Mars.
"The only direct evidence for life early in the history of a planet's evolution is that on Earth," said Grebowsky. "The earliest evidence for terrestrial life is the organic chemical structure of a rock found on the surface in Greenland. The surface was thought to be from an ancient sea floor sediment. The age of the rock was estimated to be 3.8 billion years, 700 million years from the Earth's creation.”
The video ends with an illustration of NASA's MAVEN mission in orbit around present-day Mars. MAVEN will investigate how Mars lost its atmosphere. Scheduled to be launched in November, it will arrive at Mars in September 2014.
There are several theories of how Mars was stripped of its thick atmosphere.
"Hydrodynamic outflow and ejection from massive asteroid impacts during the later heavy bombardment period (ending 4.1 billion to 3.8 billion years ago) were early processes removing part of the atmosphere, but these were not prominent loss processes afterwards," said Grebowsky. "The leading theory is that Mars lost its intrinsic magnetic field that was protecting the atmosphere from direct erosion by the impact of the solar wind."
The solar wind is a thin stream of electrically charged particles (plasma) blowing continuously from the sun into space at about a million miles per hour.
Here's the video:

NASA – An instrument onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) detected atomic oxygen in the atmosphere of Mars for the first time since the last observation 40 years ago. These atoms were found in the upper layers of the Martian atmosphere known as the mesosphere.
Atomic oxygen affects how other gases escape Mars and therefore has a significant impact on the planet’s atmosphere. Scientists detected only about half the amount of oxygen expected, which may be due to variations in the Martian atmosphere. Scientists will continue to use SOFIA to study these variations to help better understand the atmosphere of the Red Planet. – read more

1999, 29: 625-10.1023/A:1006514327249.View ArticlePubMedGoogle Scholar
- Margulis L, Mazur P, Barghoorn ES, Halvorson HO, Jukes TH, Kaplan IR: The Viking Mission: implications for life on Mars. J Mol Evol. 1979, 14: 223-232.View ArticlePubMedGoogle Scholar
- Levin GV: O2- ions and the Mars labeled release response. Science. 2001, 291: 2041-10.1126/science.291.5511.2041a.View ArticlePubMedGoogle Scholar
- Levin GV, Straat PA: Laboratory simulations of the Viking labeled release experiment: kinetics following second nutrient injection and the nature of the gaseous end product. J Mol Evol. 1979, 14: 185-197.View ArticlePubMedGoogle Scholar
- Goldfield M, Tsapin I, Nealson K: Surface-possible mechanisms and implications. In Poster Section 12: Mars Oxidants, First Astrobiology Science Conference. NASA Ames Research Center, CA, April 3–5, 2000Google Scholar
- Yen AS, Kim SS, Hecht MH, Frant MS, Murray B: Evidence that the reactivity of the Martian soil is due to superoxide ions. Science. 2000, 289: 1909-1912. 10.1126/science.289.5486.1909.View ArticlePubMedGoogle Scholar
- Quinn RC, Zent AP: Peroxide-modified titanium dioxide: a chemical analog of putative Martian soil oxidants. Orig Life Evol Biosph. 1999, 29: 59-72. 10.1023/A:1006506022182.View ArticlePubMedGoogle Scholar
- Goff H, Murmann RK: Studies on the mechanism of isotopic oxygen exchange and reduction of ferrate(VI) ion (FeO42-). J Am Chem Soc. 1971, 93: 6058-6065.View ArticleGoogle Scholar
- Lee DG, Gai H: Kinetics and mechanism of the oxidation of alcohols by ferrate ion. Can J Chem.

PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.

The oxidation of Earth’s atmosphere was one of the most important events in our planet’s history. It’s also one we don’t understand very well. New evidence has dated the event to 2.33 billion years ago and indicates it happened over a timespan of less than 10 million years.
Oxygen is so reactive that it will not stay in the atmosphere for a long period of time. This is why scientist James Lovelock once suggested that oxygen in the atmosphere of another planet would be evidence for life, although the conclusiveness of this is now debated.
It’s also why there was excitement about the discovery of oxygen on Mars this week, although the Martain concentration is low enough to allow other possible sources.
Life alone is not enough, however. For almost the first 2 billion years of life on Earth, oxygen levels are thought to have been minimal, although even this was challenged by another paper this week. Only after what is known as the Great Oxidation Event (GOE), did the planet become capable of sustaining multi-cellular organisms.
Few rocks remain from the time of the GOE, and what we have found has proven sufficiently contradictory that geologists have struggled to make sense of when, and how quickly, oxygen appeared. However, new evidence from South Africa may resolve these questions.
How long has Earth had oxygen? NASA
In Science Advances, a team led by Dr. Genming Luo of the Massachusetts Institute of Technology (MIT) reports on the results from three drill cores in the Transvaal, South Africa. All three provide a date of 2.33 billion years ago for the GOE, and indicate oxidation took between 1 million and 10 million years. Unimaginably long as a million years is to us, by geological standards, these are quite rapid.
Luo and co-authors also concluded that the concentrations of sulphate in the oceans, an indication of the presence of oxygen to bond with the sulfur, lagged the GOE by approximately 6 million years, and was a slower process.
Another of the big questions about the GOE has been whether it was caused by, or caused, radical climate change.
On this point the paper reports that “a series of glaciations took place between 2.45 and 2.2 billion years ago,” and that at least one of these “Snowball Earth” events occurred shortly before the GOE and may have precipitated it.

Mars today (despite the presence of a small amount of a liquid water) is a dry, frozen place. But this was not always the case. Ancient Mars was likely warm and wet, much like Earth. So what happened to change it? Thanks to brand new results from NASA’s MAVEN mission, announced today, we may finally know.
The Solar Winds
“When we look at ancient Mars we see a different kind of surface, an environment that was able to support water on the surface” said MAVEN principle investigator Bruce Jakovsky today. “So what happened to the carbon dioxide in that atmosphere, what happened to the water on early Mars?”
Over the last year, MAVEN has been studying Mars’ atmosphere carefully. Using that data, researchers revealed (along with the simultaneous publication of the results in Science and Geophysical Research Letters) that, under bombardment from solar winds, Mars’ atmospheric gases were being striped away.
While the solar winds don’t directly strike the planet’s surface, the solar winds have been stripping atmospheric gas around the planet steadily, coming off in bursts as Jasper Halekas, MAVEN’s lead instrument investigator explained “like the shock wave around a jet plane.”
As the solar winds carried off more and more of Mars’ atmospheric gas, like you see above, the planet was left less and less able to sustain the watery surface it once had. “The analogy I use,” Jakovsky explained, “is when I step out of the shower into the breeze, the water in my hair is just whisked away by the wind.”
Today, that loss of atmospheric gas is continuing at the rate of about 1/4 pound of gas per second. But, researchers believe that in Mars’ earlier days, as it first began to lose atmospheric gas, that rate was much higher. And even today, that rate can easily jump 10-20 times during a solar storm, like you see in this comparison between the average rates and the solar storm rates:
Is Mars Earth’s Future?
So, if Mars was a once a wet planet that lost its water along with its atmosphere, what about Earth? Should we worry that our own home might one day look like the red planet’s dry, dusty surface? Fortunately, there’s something significant standing in the way: Earth’s magnetic field.
Like Mars, Earth is also subject to powerful solar winds—and like Mars, it also loses some of its atmospheric gases.

Although subsequent measurements have shown that the present-day residual cap is not massive enough to significantly buffer surface pressures as Leighton and Murray envisioned, this concept factors heavily into the orbitally forced climate changes that have dominated much of the planet’s history.
Evidence for Climate Change
Isotopic data indicate that Mars accreted and differentiated into a core, mantle, and crust within a few tens of millions of years (e.g., Lee & Halliday, 1997; Solomon et al., 2005). The nature of the atmosphere during this time is unknown, although an early steam atmosphere and magma ocean are possible (Matsui & Abe, 1987). Major early events include the creation of the global dichotomy (e.g., McGill & Squyres, 1991), the development of a magnetic field (e.g., Acuña et al., 1999), and the formation of large impact basins (e.g., Carr, 1981). The Hellas impact basin is estimated to be 4.1 Gy (Frey, 2003)—a time that may coincide with the end of the magnetic field (Lillis et al., 2008). It also marks the approximate beginning of the geological record observable from orbiters, which has been grouped into three periods: the Noachian (4.1 to 3.7 Gy), the Hesperian (3.7 to ~3.0 Gy), and the Amazonian (~3.0 Gy to the present). Because these periods are based on crater statistics linked to cratering models, there is uncertainty in the absolute ages (e.g., Michael, 2013). These periods are also marked by distinctive surface mineralogies (Bibring et al., 2006) likely linked to the prevailing climate system, with the Noachian dominated by phylosillicates (clays), the Hesperian by sulfates, and the Amazonian by iron oxides. It is therefore convenient to frame the discussion of climate change around these geological epochs.
This is the earliest epoch and provides the most compelling evidence that the climate then was at least episodically warmer and wetter than it is today. Noachian terrains are much more eroded than younger surfaces (Carr, 1992).

"The supposed very thick atmosphere seemed to imply that you needed this big surface carbon reservoir, but the efficiency of the UV photodissociation process means that there actually is no paradox. You can use normal loss processes as we understand them, with detected amounts of carbonate, and find an evolutionary scenario for Mars that makes sense."
Source: NASA press release

But how did such a small, cold world ever have lakes and rivers of liquid water? The reigning theory was that the thin atmosphere once contained so much carbon dioxide that the greenhouse effect made the planet warm enough. To test this theory, NASA sent the Curiosity rover to the bed of an ancient lake (above) to sample the sedimentary rocks within it. Rocks that formed in an atmosphere dense with CO2 ought to show evidence of that, in the form of carbonate minerals.
The same Martian bedrock in which Curiosity found sediments from an ancient lake where microbes could have thrived is the source of the evidence adding to the quandary about how such a lake could have existed. Curiosity detected no carbonate minerals in the samples of the bedrock it analyzed. The new analysis concludes that the dearth of carbonates in that bedrock means Mars' atmosphere when the lake existed -- about 3.5 billion years ago -- could not have held much carbon dioxide.So it's back to the drawing board in trying to model the ancient atmosphere of Mars.
"We've been particularly struck with the absence of carbonate minerals in sedimentary rock the rover has examined," said Thomas Bristow of NASA's Ames Research Center, Moffett Field, California. "It would be really hard to get liquid water even if there were a hundred times more carbon dioxide in the atmosphere than what the mineral evidence in the rock tells us."

Many scientists, though certainly not all [3, 4], have concluded that results of Viking biological experiments can be interpreted as an indication of the presence of strong oxidants in the Martian soil [5–7], rather than biological activity. They suggest that these oxidants are capable of oxidizing organic materials causing release of carbon dioxide as seen in the Viking experiments. Since oxygen was also released after humidifying a sample of Martian soil, these proposed oxidants would also oxidize water. The spontaneous reduction of Ferrate(VI) in water forms molecular oxygen and Fe(III) . The rate of this reaction is strongly pH dependent . Other observations by Viking have complicated data interpretation, including the transient absorption of generated carbon dioxide, perhaps indicating an alkaline soil. Also, different thermal sensitivity of carbon dioxide and oxygen released implied that more than one oxidant might have been involved in the observed processes or that biology might indeed have been responsible for the observed results .
Goldfield, et al.  and Tsapin, et al.  suggested that the actual source of oxidative power of Martian soil could be highly redox active oxygen species formed in the atmosphere by ultraviolet (UV) irradiation, and Hunten  examined this hypothesis much earlier. Further, these oxidative equivalents may then be stabilized in the form of high oxidation states of some elements that are particularly abundant in Martian soil. The most likely element is iron, which is thought to represent a major fraction of the Martian soil matrix [12, 13]. Iron has a set of oxidation states between +2 and +6, with the higher oxidation states being very strong oxidants. The reduction potential of FeO42- in acidic conditions has been determined to be E0 = +2.20 V and in alkaline conditions E0 = +0.72 V . Thus, these authors [5, 10] proposed that Fe(VI) as ferrate dianion FeO42-, which is more stable under alkaline rather than acidic conditions, might be an important component of the pool of Martian oxidants. They demonstrated that Fe(VI) displays the essential features of organic oxidation to carbon dioxide and water decomposition to oxygen that were found with Martian soil during the Viking biology experiments. Goldfield, et al.

(2014). Warming early Mars with CO2 and H2. Nature Geoscience, 7, 59–63.
- Rivera-Hernández, F., & Palucis, M. C. (2019). Do deltas along the crustal dichotomy boundary of Mars in the Gale Crater region record a northern ocean? Geophysical Research Letters, 46, 8689–8699.
- Rodriguez, J. A. P., Fairén, A. G., Tanaka, K. L., Zarroca, M., Linares, R., Platz, T., Komatsu, G., Miyamoto, H., Kargel, J. S., Yan, J., Gulick, V., Higuchi, K., Baker, V. R., & Glines, N. (2016). Tsunami waves extensively resurfaced the shorelines of an early Martian ocean. Scientific Reports, 6, 25106.
- Scherf, M., & Lammer, H. (2021). Did Mars possess a dense atmosphere during the first ~400 million years? Space Science Reviews, 217, 2.
- Segura, T., Toon, O. B., & Colaprete, A. (2008). Modeling the environmental effects of moderate-sized impacts on Mars. Journal of Geophysical Research, 113.
- Sholes, S. F., Montgomery, D. R., & Catling, D. C. (2019). Quantitative high-resolution reexamination of a hypothesized ocean shoreline in Cydonia Mensae on Mars. Journal of Geophysical Research: Planets, 1224, 316–336.
- Smith, I. B., Putzig, N. E., Holt, J. W., & Phillips, R. J. (2016). An ice age recorded in the polar deposits of Mars. Science, 352, 1075–1078.
- Smith, P. H., & the Phoenix Science Team. (2009). Water at the Phoenix landing site [No. 1329]. Paper presented at the 40th Lunar and Planetary Science Conference.

The Case of the Missing Mars Water
The Case of the Missing Mars Water Plenty of clues suggest that liquid water once flowed
on Mars --raising hopes that life could have arisen there-- but
the evidence remains inconclusive and sometimes contradictory
January 5, 2001 -- Mars may once have been a very wet place. A host of clues remain from an earlier era, billions of years ago, hinting that the Red Planet was host to great rivers, lakes and perhaps even an ocean. But some of the clues are contradictory -- they don't all fit together in a coherent whole. Little wonder, then, that the fate of water on Mars is such a hotly debated topic.
The reason for the intense interest in Martian water is simple: Without water, there can be no life as we know it. If it has been 3.5 billion years since liquid water was present on Mars, the chance of finding life there is remote. But if water is present on Mars now, however well hidden, life may be holding on in some protected niche.
Right: Sedimentary rock layers like these in Mars's Holden Crater suggest that the Red Planet was once home to ancient lakes. [more information]
Based on what we have observed so far, Mars today is a frozen desert. It's too cold for liquid water to exist on its surface and too cold to rain. The planet's atmosphere is also too thin to permit any significant amount of snowfall.
Even if some internal heat source warmed the planet up enough for ice to melt, it wouldn't yield liquid water. The Martian atmosphere is so thin that even if the temperature rose above freezing the ice would change directly to water vapor.
Signs of Heavy Flooding
What caused these giant floods? Was it a climate change, perhaps brought about by a change in Mars's orbit? Or was the planet's own internal heat responsible? And, whatever mechanism caused the floods in the first place, where has all that water gone? Was it absorbed into the ground where it remains today, frozen? Or did it dissipate into the Martian atmosphere, where it was subsequently lost to space? No-one knows for certain the answers to these questions.
Some scientists believe that the catastrophic floods that carved the outflow channels occurred nearly simultaneously, releasing such vast quantities of water that they merged into an ocean that covered the northern lowlands.

Based on Earth analogs, hydrothermal systems on Mars would be highly attractive for their potential for preserving organic and inorganic biosignatures. For this reason, hydrothermal deposits are regarded as important targets in the exploration for fossil evidence of ancient Martian life.
Methane[edit | hide | edit source]
Possible trace amounts of methane in the atmosphere of Mars were first discovered in 2003 with earth based telescopes and fully verified in 2004 by the ESA Mars Express spacecraft in orbit around Mars. As methane is an unstable gas, its presence indicates that there must be an active source on the planet in order to keep such levels in the atmosphere. It is estimated that Mars must produce 270 ton/year of methane, but asteroid impacts account for only 0.8% of the total methane production. Although geologic sources of methane such as serpentinization are possible, the lack of current volcanism, hydrothermal activity or hotspots are not favorable for geologic methane. It has been suggested that the methane was produced by chemical reactions in meteorites, driven by the intense heat during entry through the atmosphere. Although research published in December 2009 ruled out this possibility, research published in 2012 suggest that a source may be organic compounds on meteorites that are converted to methane by ultraviolet radiation.
The existence of life in the form of microorganisms such as methanogens is among possible, but as yet unproven sources. Methanogens do not require oxygen or organic nutrients, are non-photosynthetic, use hydrogen as their energy source and carbon dioxide (CO2) as their carbon source, so they could exist in subsurface environments on Mars. If microscopic Martian life is producing the methane, it probably resides far below the surface, where it is still warm enough for liquid water to exist.
Since the 2003 discovery of methane in the atmosphere, some scientists have been designing models and in vitro experiments testing growth of methanogenic bacteria on simulated Martian soil, where all four methanogen strains tested produced substantial levels of methane, even in the presence of 1.0wt% perchlorate salt. The results reported indicate that the perchlorates discovered by the Phoenix Lander would not rule out the possible presence of methanogens on Mars.
Research at the University of Arkansas presented in June 2015 suggested that some methanogens could survive on Mars's low pressure.

Consequently, alternative ideas for warming early Mars involving impacts, volcanism, clouds, and orbital changes have been suggested. Yet a widely agreed upon solution remains elusive. In more recent geological times, thick polar layered terrains, debris-covered glaciers, and latitude-dependent mantle deposits indicate that ice ages have come and gone similar to those on Earth. Although rainfall is not implicated, cyclic mobilization and redistribution of large surface ice reservoirs, a process similar to what occurred on Earth, is implicated. And for the vast majority of the billions of years of Mars’ existence, a gradually brightening Sun, chaotic orbital variations, and episodic volcanism strongly implicate an ever-changing climate system. Clearly, Mars today is not representative of what it was in the past. This article reviews the evidence for climate change on Mars and constructs a picture of how its climate might have evolved over time.
Before the spacecraft era, telescopic observers of Mars worked out its size, basic orbital properties, and noted its variable features including clouds and polar ice caps. Most famously, Percival Lowell claimed to see canals crisscrossing the surface that in his mind were constructed by intelligent beings trying to survive on a drying planet (Figure 1; Lowell, 1906). Lowell’s ideas were immensely popular and generated much interest in the red planet, but they were not scientifically sound. He recognized that the atmosphere was thin, for example, but argued for a warm climate, an inconsistency pointed out a year later by Alfred Wallace (1907).
Nevertheless, the possibility of life on Mars remained foremost in public discourse until the Mariner flybys of the 1960s. These missions revealed a much harsher Martian environment than Lowell envisioned. The seasonal polar caps were made of CO2 ice, not water ice; its atmosphere was primarily CO2, not nitrogen or oxygen; and the surface pressure was estimated to be very low (~7 hPa), much lower than previously thought. Most important, craters—not canals—dominated its surface. There was no evidence for life of any kind much less an advanced civilization engaged in a global-scale canal project. The landscape instead resembled the Moon, and like the Moon, it suggested that Mars was a dead planet whose story ended soon after it formed.
This perception changed with Mariner 9, the first spacecraft to orbit Mars giving a much greater view of its surface.

NASA’s Curiosity rover continues to make discoveries that challenge our understanding of the Martian environment. The latest puzzle confusing scientists is the variation of oxygen levels on the planet’s surface, as detected Curiosity’s portable chemistry lab, Sample Analysis at Mars (SAM).
While SAM was moving around the Gale Crater, Curiosity discovered the Martian atmosphere has a composition at the surface of 95% by volume of carbon dioxide (CO2), 2.6% molecular nitrogen (N2), 1.9% argon (Ar), 0.16% molecular oxygen (O2), and 0.06% carbon monoxide (CO). The nitrogen and argon levels keep a predictable seasonal pattern, changing relative to the amount of carbon dioxide. The levels of oxygen, though, didn’t conform to expected patterns, rising by as much as 30% over spring and summer.
The varying oxygen levels have scientists asking questions. “The first time we saw that, it was just mind-boggling,” Sushil Atreya, professor of climate and space sciences at the University of Michigan, said in a statement
The scientists attempted various hypotheses to explain the oxygen variation. They checked whether the SAM instrument was functioning correctly and looked at whether carbon dioxide molecules could be breaking apart in the atmosphere to create oxygen. Neither approach yielded results.
“We’re struggling to explain this,” Melissa Trainer, a planetary scientist at NASA’s Goddard Space Flight Center and leader of the research, said in the statement. “The fact that the oxygen behavior isn’t perfectly repeatable every season makes us think that it’s not an issue that has to do with atmospheric dynamics. It has to be some chemical source and sink that we can’t yet account for.”
One factor for consideration is that the oxygen levels are related to another Martian puzzle: The fluctuating levels of methane on the planet. There is also expected seasonal variations in methane levels, and Curiosity has detected spikes of methane of up to 60% at some times. Scientists still can’t explain this finding either, but they may have found a link between methane and oxygen levels: It seems like the two gases fluctuate together at certain times.
“We’re beginning to see this tantalizing correlation between methane and oxygen for a good part of the Mars year,” Atreya said. “I think there’s something to it. I just don’t have the answers yet. Nobody does.”

NASA'sCuriosityrover has found new evidence preserved in rocks on Mars that suggests the planet could have supported ancient life, as well as new evidence in the Martian atmosphere that relates to the search for current life on the Red Planet.
"Curiosity has shown that Gale crater was habitable around 3.5 billion years ago, with conditions comparable to those on the early Earth, where life evolved around that time", she wrote.
Apart from the organic evidences, Curiosity also found abnormal levels of methane in the atmosphere of Mars. It previously found hints of methane and organic compounds, but these findings are the best evidence yet. "Curiosity has not determined the source of the organic molecules", explains Eigenbrode. The press conference will be headed by the big NASA researchers along with people who were directly working on the samples Curiosity has been diligently gathering on Mars.
The studies were conducted using evidence collected by NASA's Curiosityrover, which is now rolling around the Martian surface.
The amount of methane peaked at the end of summer in the northern hemisphere at about 2.7 times the level of the lowest seasonal amount.
On Thursday NASA had made an announcement, stating that a recent finding seems to confirm that there used to be life on Mars, and maybe even still is. "That means Mars today is not a 'dead planet, ' but somewhere underground there are reactions occurring today that release and absorb an atmospheric gas that is nearly always related to warm water or life on Earth". The molecules in the mudstone could have once enabled life to form in lakes when Mars still had liquid water on its surface and the methane could have been produced by life.
Despite the fact that it is still not clear how these molecules were created, NASA emphasized that these kinds of particles could have been the food source for hypothetical microbial life on Mars. Mars scientists have long feared that any organics would be extremely tough to find.
Attention, however this does not mean that life exists or has ever existed on the Red planet! "But it gave us a lot of anticipation that, if we can find these molecules here, perhaps we're going to come across other layers of rock that have more organics in them".
The study, which has been in place for around six years (the equivalent of almost three martian years), shows that low levels of methane within the crater repeatedly peak in warm, summer months and drop in the winter every year.

The larger planet retained its internal heat, and with it a hot core of partially molten metal. As Earth rotates, the molten core churns and acts as a dynamo, generating a strong magnetic field--something Mars lacks. Unshielded, the Martian surface receives a heavy dose of deadly cosmic rays and is buffeted by the solar wind, which over time has stripped away Mars's atmosphere. Had Earth formed nearer to Jupiter, conditions might have turned out less favorably for its inhabitants. "The evolution and habitability of the planet are direct consequences of its initial conditions — how big it is, and where it is in the Solar System," Ebel says.
In March 2004, the NASA rovers Spirit and Opportunity found evidence that, like Earth, Mars once possessed large bodies of briny water, perhaps even a sea, on its surface. The discovery of acid-sulphate salts on the Martian surface indicate that the briny sea evaporated at some point. But when that occurred, and where all the water went, is unclear. "What happened to the water?" Ebel muses. "We don't know. The key missing evidence is the timing."
One possibility is that the water wound up in the polar ice caps, both of which are now known to contain frozen water in addition to frozen carbon dioxide, or "dry ice". "There's a lot of water in there, more than was previously thought," Ebel says. Scientists are trying to model the Martian atmosphere, to determine how carbon dioxide and water move around the surface of Mars and, by working backward in time, where it came from and went. But the orbit of Mars is far more eccentric than Earth's, thanks to the gravitational influence of Jupiter. As a result, Ebel explains, "Figuring out which part of the planet was cooler and which warmer, and when in history, is a challenging puzzle."
There's also a strong possibility that water, frozen or liquid, may still exist beneath the surface of Mars. (The Martian climate is too cold for liquid water to exist aboveground.) The European Space Agency's Mars Express orbiter is equipped with ground-penetrating radar, which can detect signs of frozen water beneath the rocky Martian surface — if it's there to be found.
The existence of both volcanic activity and water on Mars raise the tantalizing possibility that the planet might have harbored life at one time in its history.

- Formisano, Vittorio; Atreya, Sushil; Encrenaz, Thérèse; Ignatiev, Nikolai; Giuranna, Marco (2004). "Detection of Methane in the Atmosphere of Mars". Science. 306 (5702): 1758–61. Bibcode:2004Sci...306.1758F. doi:10.1126/science.1101732. PMID 15514118.
- Krasnopolsky, Vladimir A.; Maillard, Jean Pierre; Owen, Tobias C. (2004). "Detection of methane in the martian atmosphere: Evidence for life?". Icarus. 172 (2): 537–47. Bibcode:2004Icar..172..537K. doi:10.1016/j.icarus.2004.07.004.
- "Mars Express confirms methane in the Martian atmosphere" (Press release). ESA. March 30, 2004. Archived from the original on February 24, 2006.
- Moran, Mark; Miller, Joseph D.; Kral, Tim; Scott, Dave (2005). "Desert methane: Implications for life detection on Mars". Icarus. 178: 277–80. Bibcode:2005Icar..178..277M. doi:10.1016/j.icarus.2005.06.008.
- Krasnopolsky, Vladimir A. (2006). "Some problems related to the origin of methane on Mars". Icarus. 180 (2): 359–67. Bibcode:2006Icar..180..359K. doi:10.1016/j.icarus.2005.10.015.
- "Planetary Fourier Spectrometer website". Mars Express. ESA. Archived from the original on May 2, 2013.[verification needed]
- "Hunting for young lava flows". Geophysical Research Letters. Red Planet. June 1, 2011. Archived from the original on October 4, 2013.
- Court, Richard W.; Sephton, Mark A. (2009).

There’s never been much mystery surrounding the murder of Mars. Once a warm, wet world, Mars lost its magnetic field more than 4 billion years ago when its outer core cooled, shutting off the dynamo that kept the field in place. That exposed the planet to the solar wind, which clawed away at the atmosphere; and that in turn allowed the planet’s water to sputter off into space. To look at Mars today is to see a desert world, stamped with the dry riverbeds, delicate deltas and deep ocean basins hinting at the water that is no more.
At least, that’s the long-accepted view. But according to a study published Mar. 16 in Science by a team of researchers at the California Institute of Technology, that scenario might be all wrong. Mars is dry, alright—or at least it appears to be. But the researchers say much of its water—from 30% to a staggering 99% of it—is still there. It simply retreated into the martian rocks and clay rather than escaping into space.
Just how much water once flowed across the surface of Mars is expressed by a unit of measure known as “global equivalent layer” (GEL)—the depth that the water would be if it were not sequestered in basins and rivers, but instead were spread evenly across the entire planet. The best estimates for Mars’s original GEL is anywhere from 100 to 1,500 meters (330 to 4,900 ft). That’s an awfully wide range, but today it’s considerably narrower: the modern-day water on the planet’s surface—almost entirely trapped in its polar ice caps—has a GEL of just 20 to 40 m.
When Mars lost its atmosphere, all that original water had to go somewhere. The evaporation-to-space route was always the easiest explanation—but it’s a flawed one, too. The problem, as the Caltech researchers knew, involves hydrogen. As Martian water molecules rise into and then escape from the atmosphere, they disassociate into free hydrogen and oxygen atoms. An oxygen atom in water is just an oxygen atom, but hydrogen comes in two forms: ordinary hydrogen (with a single proton in its nucleus) and deuterium (with a proton and a neutron). Water molecules made of heavier deuterium instead of ordinary hydrogen are known, straightforwardly enough, as heavy water.

1993, 71: 1394-1400.View ArticleGoogle Scholar
- Tsapin AI, Goldfeld MG, McDonald GD, Nealson KH, Moskovitz B, Solheid P, Kemner KM, Kelly SD, Orlandini KA: Iron(VI): hypothetical candidate for Martian oxidant. Icarus. 2000, 147: 68-78. 10.1006/icar.2000.6437.View ArticleGoogle Scholar
- Hunten DM: Possible oxidant sources in the atmosphere and surface of Mars. J Mol Evol. 1979, 14: 71-78.View ArticlePubMedGoogle Scholar
- Rieder R, Economou T, Wanke H, Turkevich A, Crisp J, Bruckner J, Dreibus G, McSween HY: The chemical composition of Martian soil and rocks returned by the mobile alpha proton X-ray spectrometer: preliminary results from the X-ray mode. Science. 1997, 278: 1771-1774. 10.1126/science.278.5344.1771.View ArticlePubMedGoogle Scholar
- Banin A, Clark BC, Wanke H: Surface chemistry and mineralogy. In: Mars. Edited by: Keiffer HH, Jakosky BM, Snyder CW, Matthews MS. 1992, Tucson, The University of Arizona PressGoogle Scholar
- Wood RH: The heat, free energy, and entropy of the ferrate(VI) ion. J Amer Chem Soc. 1958, 80: 2038-2041.View ArticleGoogle Scholar
- Boynton WV, Feldman WC, Squyres SW, Prettyman TH, Bruckner J, Evans LG, Reedy RC, Starr R, Arnold JR, Drake DM, Englert PA, Metzger AE, Mitrofanov I, Trombka JI, D'Uston C, Wanke H, Gasnault O, Hamara DK, Janes DM, Marcialis RL, Maurice S, Mikheeva I, Taylor GJ, Tokar R, Shinohara C: Distribution of hydrogen in the near surface of Mars: evidence for subsurface ice deposits. Science. 2002, 297: 81-85.

- NASA revealed Thursday that solar wind has stripped away Mars' atmosphere
- The findings may give clues into what we can expect for Earth
(CNN)We now know more about what happened to Mars' climate.
NASA announced on Thursday several major scientific findings by its MAVEN spacecraft that reveal significant details on the fate of the Martian atmosphere.
Scientists have known that billions of years ago, Mars was a wet, warm planet with a thick atmosphere that protected it. The Martian landscape once had water flowing through its long rivers that spilled out into lakes and oceans.
That world is a stark contrast to the dry and bitter cold planet we know it as today. The question researchers have pondered for ages is: What happened to cause such a major transformation?
"Quoting Bob Dylan: 'The answer, my friend, is blowing in the wind,' " said Michael Meyer, lead scientist for the Mars Exploration Program at NASA Headquarter during the announcement.
New measurements from the MAVEN, Mars Atmosphere and Volatile Evolution, show solar winds have stripped ions from the Martian atmosphere. Solar wind -- charged particles from the Sun -- have removed gases like oxygen and carbon dioxide from the planet, important elements for understanding the potential for life, according to NASA.
The findings could mean there was big atmospheric loss early in the planet's history.
Mars' atmospheric fate could theoretically happen on Earth which is also losing ions, but NASA said during the conference that our planet is fine for now because of its magnetic field.
The MAVEN has also discovered auroras on Mars that are similar to Earth's northern lights. On our planet, auroras form when charged particles from the solar winds enter Earth's magnetic field and travel to the poles where the particles collide with atoms of gas in the atmosphere.
But the auroras on Mars may be caused by what is left of the magnetic field on the planet's crust, which means these northern lights are spread out across a bigger area.
Another major finding shows that Mars' notorious dust problem is believed to be interplanetary in origin, meaning from another planet. Scientists came to this conclusion based on the grains and distribution of dust on Mars' surface, which ruled out Martian moons Phobos and Deimos as the culprits.
The MAVEN has been on a mission to study Mars' upper atmosphere since its arrival to the planet's orbit in September 2014. Tasked with finding how Mars' climate changed in the last 4 billion years, it's possible we're closer to understanding future habitability on the planet.

When there was a magnetic field, the atmosphere would have been protected from erosion by solar wind, which would ensure the maintenance of a dense atmosphere, necessary for liquid water to exist on the surface of Mars. The loss of the atmosphere was accompanied by decreasing temperatures. A part of the liquid water inventory sublimed and was transported to the poles, while the rest became trapped in a subsurface ice layer.
Observations on Earth and numerical modeling have shown that a crater-forming impact can result in the creation of a long lasting hydrothermal system when ice is present in the crust. For example, a 130 km large crater could sustain an active hydrothermal system for up to 2 million years, that is, long enough for microscopic life to emerge.
Soil and rock samples studied in 2013 by NASA's Curiosity rover's onboard instruments brought about additional information on several habitability factors. The rover team identified some of the key chemical ingredients for life in this soil, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and possibly carbon, as well as clay minerals, suggesting a long-ago aqueous environment — perhaps a lake or an ancient streambed — that was neutral and not too salty. On December 9, 2013, NASA reported that, based on evidence from Curiosity studying Aeolis Palus, Gale Crater contained an ancient freshwater lake which could have been a hospitable environment for microbial life. The confirmation that liquid water once flowed on Mars, the existence of nutrients, and the previous discovery of a past magnetic field that protected the planet from cosmic and Solar radiation, together strongly suggest that Mars could have had the environmental factors to support life. However, the assessment of past habitability is not in itself evidence that Martian life has ever actually existed. If it did, it was probably microbial, existing communally in fluids or on sediments, either free-living or as biofilms, respectively.
Present[edit | hide | edit source]
Present day life on Mars could occur kilometers below the surface in the hydrosphere, or in subsurface geothermal hot spots, or it could occur on or near the surface. The permafrost layer on Mars is only a couple of centimeters below the surface. Salty brines can be liquid a few centimeters below that but not far down. Most of the proposed surface habitats are within centimeters of the surface. Any life deeper than that is likely to be dormant.

The researchers made a detailed analysis of the compounds involved in the clays, comparing them to those found in thousands of lakebeds on Earth. The time it takes for various chemicals to mix in with the clays is an important factor as well, as it affects how much of them we’d observe now.
The researchers conclude that the Martian atmosphere at the time the clays were formed had a lot more CO2 than the lower limits of previous estimates. But the numbers are still fall far short of what's needed to keep the temperature above freezing.
This doesn't definitively rule out the greenhouse explanation; certain environmental processes the researchers are not considering could have changed the composition of the clays. Where does that leave things? It's largely the same predicament as before. This study adds more evidence that Mars didn’t have enough CO2 in its atmosphere to have kept water liquid from 3.8 to 3.1 billion years ago. So either warming was driven by some other mechanism, or somehow the water was able to flow despite temperatures that were typically below freezing. Either conclusion would be interesting.
The data also provides more information about a critical period in the history of Mars—around the time these clays were formed, Mars was rapidly losing its atmosphere. This site is among the youngest of the now-dry sites of surface water yet discovered, meaning these clays were probably formed during the tail end of this process. Those were essentially the last days of the wet Mars.

The martian atmosphere bulk composition is not like any other known source of gas. Also, the Viking landers found that Mars atmosphere has unusual isotopic abundances; it is rich in nitrogen with weight 15 (15N) compared to nitrogen with weight 14 (14N), and relatively rich in two isotopes that form during radioactive decay of other elements, 40Ar and 129Xe. Telescopic observation from Earth also showed that the martian atmosphere is very rich in heavy hydrogen (also called deuterium, D) compared to the Earth. Again, this mix of isotopic abundances is not like any other known source of gas.
This martian atmosphere gas was first discovered in the Antarctic meteorite EETA79001 (Bogard and Johnson, 1983), and traces of it are present in almost all of the martian (SNC) meteorites.
B. Is this martian atmosphere in ALH 84001?
Yes. This same martian atmosphere gas is also present in ALH 84001, which has hydrogen rich in deuterium, nitrogen rich in 15N, argon rich in 40Ar, and xenon rich in 129Xe (Miura and Sugiura, 1995; Gilmour et al., 1995, 1996; Grady et al., 1996; Leshin et al., 1996; Miura et al., 1995; Swindle et al., 1995).
C. Is there other evidence that the martian meteorites are from Mars?
All circumstantial. The martian meteorites except ALH 84001, the SNCs, all crystallized from lava less than 1300 million years ago. The only objects in the solar system with volcanoes active so recently are Venus, Earth, Mars, and Io. The SNCs arent from the Earth because their oxygen isotope compositions are utterly distinct from anything on Earth. Theyre probably not from Venus, because most of the SNC meteorites contain extraterrestrial clays or water-bearing minerals, and they could not have formed on Venuss hot surface. Io remains possible, but pretty unlikely as the escape velocity for a rock near Jupiter is so high.
Although ALH 84001 is not young like the other SNCs, it is linked to them in other ways.

Argon lost to interactions with solar wind hints at transformed climate
The Martian atmosphere definitely had more gas in the past.
Data from NASA’s MAVEN spacecraft indicate that the Red Planet has lost most of the gas that ever existed in its atmosphere. The results, published in the March 31 Science, are the first to quantify how much gas has been lost with time and offer clues to how Mars went from a warm, wet place to a cold, dry one.
Mars is constantly bombarded by charged particles streaming from the sun. Without a protective magnetic field to deflect this solar wind, the planet loses about 100 grams of its now thin atmosphere every second (SN: 12/12/15, p. 31). To determine how much atmosphere has been lost during the planet’s lifetime, MAVEN principal investigator Bruce Jakosky of the University of Colorado Boulder and colleagues measured and

The presence of near-surface ice at mid to high latitudes is corroborated by the Odyssey orbiter data (Boynton et al., 2002; Feldman et al., 2002; Mitrofanov et al., 2002), the Phoenix lander (Mellon et al., 2009; Smith et al., 2009), and images of fresh impact craters (Byrne et al., 2009). The inferred ice abundances from these data are generally in excess of that expected from the filling of pore space alone, suggesting that the ice is very pure. Although the tropics are generally ice-free, fan-shaped deposits on the northwest flanks of the Tharsis volcanoes appear to be remnants of cold-based tropical glaciers that existed in the past (Head & Marchant, 2003). Global circulation modeling simulations show that such glaciers could form at times of high obliquity (Forget et al., 2006). These simulations clearly demonstrate that obliquity variations can mobilize and redistribute surface ice deposits from the polar regions to the tropics. Thus, there is ample evidence for Amazonian climate change, and a plausible forcing mechanism has been identified.
Theories of Climate Evolution
The origin and evolution of the Martian atmosphere and climate system are not yet well understood, but there are plausible scenarios (e.g., Lammer et al., 2013). The following is intended to provide an overview of such scenarios, recognizing that uncertainties remain and alternatives may emerge. The narrative is chronological and includes geophysical topics relevant to the discussion. A timeline is given in Figure 15.
From isotope systematics of NWA 7034, a 4.43-Gy-old brecca meteorite from Mars known as “Black Beauty,” accretion, core formation, and magma ocean crystallization were completed less than 20 My after the formation of the solar system (Bouvier et al., 2018). Thus, a stable primordial crust existed on Mars very early in its history. During accretion, impact devolatilization probably created a temporary steam atmosphere that could have contained many kilometers (GEL) of water (Elkins-Tanton et al., 2005). Under these circumstances, the high extreme ultraviolet (EUV) output of the young Sun would have powered an intense phase of hydrodynamic escape, leading to removal of most of the steam atmosphere.

further propose that the presence of a strong oxidant such as ferrate would make the Martian surface self-sterilizing, eliminating the possibility for detection of life, or its remnants, on that planet. In support of their hypothesis, they conducted spectral and polymerase chain reaction (PCR) experiments with Fe(VI), finding that it destroys DNA, nucleotides, proteins, and amino acids.
It is quite possible that iron in the +5 and/or +6 oxidation states is present in the soil of Mars. However, recent observations by the Mars Odyssey orbiter indicate that significant amounts of water ice exist at or near the surface of Mars . Since transient temperatures above freezing occur at some locations on Mars , this water likely would be present at least briefly in the liquid form. Under slightly alkaline conditions, as found on Mars, and in the presence of liquid water, Fe(VI) reacts quickly with water and is oxidized to Fe(III). Thus, in regions where liquid water forms even briefly, Fe(VI) is less likely to exist. However, Mars is a relatively large planet, and conditions across its surface vary. We cannot assume that iron exists in the same oxidation state(s) everywhere on Mars. It is possible that some regions of Mars might harbor Fe(V) and Fe(VI), while regions with a frequent occurrence of liquid water might be dominated by Fe(III). Also, it is possible the Fe(VI) if removed might be reformed in a continuing cycle through interactions with the planet's atmosphere.
Stoker and Bullock  examined the oxidation of glycine under simulated Martian conditions and concluded that any organic matter brought to the Mars surface by meteorites likely would be destroyed by UV radiation faster than it might be delivered. They further suggested that no organic compounds found on Mars by the Viking Lander Gas Chromatograph Mass Spectrometer experiment could be explained without invoking the presence of strong oxidants in the surface soils. They felt their estimates of the organic destruction rate caused by irradiation at the Mars surface were an upper limit for a globally averaged biomass production rate that might be comparable to the slow-growing cryptoendolithic microbial communities found in dry Antarctica deserts .
An alternative hypothesis is that given the possible presence of ferrate in the soil, the present environmental conditions on Mars are not highly conducive to ferrate-based oxidation reactions, including those potentially affecting dormant and hostile-environment-resistant life forms.

Mars has lost at least half its atmosphere since the planet’s inception, Curiosity confirms. Mars’ atmosphere is 100 times thinner than Earth’s. Other than shielding life from harmful UV radiation, atmosphere also controls the fluctuations in climate. Because Mars’ atmosphere contains more heavier varieties of carbon dioxide than lighter ones, the ratio suggest the planet has sadly lost much of its atmosphere. Mars’ thin atmosphere has nearly untraceable amounts of methane, only a few parts of methane per billion parts of Martian atmosphere. Microbes like bacteria emit methane. In fact, 95% of methane on Earth is produced by biological processes. Though Curiosity failed to find traces of methane in Gale Crater, Mars may yet host methane elsewhere.
Curiosity used its SAM instruments (Sample Analysis at Mars) and TLS (Tunable Laser Spectrometer). In the near future, SAM will analyze its first solid sample to search for organic compounds in rocks.
In addition, air samples from Curiosity match ones from trapped air bubbles in meteorites found on Earth. Ergo, those meteorites definitely originated from Mars. 1 billion years ago, a large asteroid collided into Mars and split into fragments.
The latest of Curiosity’s analyses show that the Martian minerals is similar to “weathered basaltic salts of volcanic origin in Hawaii.” Curiosity’s CheMin (Chemistry and Mineralogy) instrument refines and identifies minerals in X-ray diffraction analysis on Mars. X-ray diffraction records hows minerals’ internal structures’ crystals react with X-rays. Identifying minerals in rocks and soil is crucial in assessing past environmental conditions. Each mineral has evidence of its unique formation. These minerals have similar chemical compositions but different structures and properties. The samples taken at “Rocknest” were consistent with scientists’ initial ideas of the deposits in Gale Crater. Ancient rocks suggest flowing water, while minerals in younger soil suggest limited interaction with water.
“NASA Rover’s First Soil Studies Help Fingerprint Martian Minerals First X-ray View of Martian Soil” JPL Caltech. JPL, 30 Oct 2012. Web. 5 Nov 2012.
Curiosity first discovered “Jake Matijevic,” the pyramid rock on Mars, on September 19, 2012, but on October 11, 2012, NASA released a report on the chemical composition of this unusual rock.

Life on Mars
|This article is a clone of a Wikipedia article. It has not yet been vetted by our editors.|
|This article is one of a series on:|
|Life in the Universe|
|Habitability in the Solar System|
|Life outside the Solar System|
The possibility of life on Mars is a subject of significant interest to astrobiology due to the planet's proximity and similarities to Earth. To date no proof has been found of past or present life on Mars. However, there is strong evidence that the ancient surface environment of Mars had seas in the northern hemmisphere, and abundant liquid water and may have been habitable for microorganisms. Since 2008 then evidence has also been building for the presence of traces of thin filims of liquid water in near surface layers/ Most of it is expected to be very salty, and including more reactive cholorates, perchlorates and sulfates instead of the chlorides and sulfides of Earth, but some of it may possibly be habiable for microbes and lichens in microhabitats. The atmosphere also may have enough humidity at times for lichens to survive in semi-shade on the surface according to some experiments at DLR. The existence of habitable conditions does not necessarily indicate the presence of life.
Scientific searches for evidence of life began in the 19th century, and they continue today via telescopic investigations and landed missions. While early work focused on phenomenology and bordered on fantasy, modern scientific inquiry has emphasized the search for water, chemical biosignatures in the soil and rocks at the planet's surface, and biomarker gases in the atmosphere. On November 22, 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior.
Mars is of particular interest for the study of the origins of life because of its similarity to the early Earth. This is especially so since Mars has a cold climate and lacks plate tectonics or continental drift, so it has remained almost unchanged since the end of the Hesperian period. At least two thirds of Mars's surface is more than 3.5 billion years old, and Mars may thus hold the best record of the prebiotic conditions leading to abiogenesis, even if life does not or has never existed there.

Earth’s oxygen levels rose and fell more than once hundreds of millions of years before the planetwide success of the Great Oxidation Event about 2.4 billion years ago, new research from the University of Washington shows.
The evidence comes from a new study that indicates a second and much earlier “whiff” of oxygen in Earth’s distant past — in the atmosphere and on the surface of a large stretch of ocean — showing that the oxygenation of the Earth was a complex process of repeated trying and failing over a vast stretch of time.
The finding also may have implications in the search for life beyond Earth. Coming years will bring powerful new ground- and space-based telescopes able to analyze the atmospheres of distant planets. This work could help keep astronomers from unduly ruling out “false negatives,” or inhabited planets that may not at first appear to be so due to undetectable oxygen levels.
“The production and destruction of oxygen in the ocean and atmosphere over time was a war with no evidence of a clear winner, until the Great Oxidation Event,” said Matt Koehler, a UW doctoral student in Earth and space sciences and lead author of a new paper published the week of July 9 in the Proceedings of the National Academy of Sciences.
“These transient oxygenation events were battles in the war, when the balance tipped more in favor of oxygenation.”
In 2007, co-author Roger Buick, UW professor of Earth and space sciences, was part of an international team of scientists that found evidence of an episode — a “whiff” — of oxygen some 50 million to 100 million years before the Great Oxidation Event. This they learned by drilling deep into sedimentary rock of the Mount McRae Shale in Western Australia and analyzing the samples for the trace metals molybdenum and rhenium, accumulation of which is dependent on oxygen in the environment.
Now, a team led by Koehler has confirmed a second such appearance of oxygen in Earth’s past, this time roughly 150 million years earlier — or about 2.66 billion years ago — and lasting for less than 50 million years. For this work they used two different proxies for oxygen — nitrogen isotopes and the element selenium — substances that, each in its way, also tell of the presence of oxygen.
“What we have in this paper is another detection, at high resolution, of a transient whiff of oxygen,” said Koehler.

In turn, combination of chlorine with metal ions requires virtually no hydrogen ions and therefore vanishingly little water in the moon, otherwise chlorine would have been combined in HCl and not subject to any fractionation when that volatilised on eruption. So that seems settled, then…
Carbonates on Mars
Ancient valley systems, huge water-carved gorges and sedimentary deposits signify with little room for doubt that early in its history Mars was wet; it must therefore have been warm. A thick CO2-rich atmosphere seems obligatory to give the kind of greenhouse warming that prevented Earth from freezing over when the young Sun was weaker than now. The question is, where did the CO2 go so that the planet became chilled? Gravity on Mars is sufficient to have retained the gas, unlike water vapour that dissociates to hydrogen and oxygen, of which hydrogen easily escapes even a much stronger gravitational field. A consensus is developing that it resides in carbonate minerals. The other likely greenhouse gas is sulfur dioxide, for whose drawdown there is ample evidence in the form of sulfates detected from orbit and by surface rovers. Carbonates have a relatively simple, and unique spectrum of reflected solar radiation, with an absorption feature at a wavelength around 2.3 micrometres. Carbonates have been detected on Mars using orbital hyperspectral imaging, but only in patches. The NASA rovers rely on serendipity for any discovery, yet Spirit did stumble on a large carbonate-rich outcrop identified by its on-board Mössbauer spectrometer (Morris, R.V. and 12 others 2010. Identification of carbonate-rich outcrops on Mars by the Spirit rover. Science, v. 329, p. 421-424). It appears to be a Fe-Mg variety in association with olivines, and carbonate makes up to 34 % of part of the outcrop. The texture is granular, yet the area abounds with evidence for hydrothermal activity in the form of sulfates and silica-rich materials, implying that some kind of circulation system deposited the carbonates. The associated olivine is odd, as that mineral is prone to rapid breakdown to serpentines in the presence of water.

It's Mars, Jim, but not as we know it
Everything you knew about Mars is wrong, or nearly everything, say European and US space scientists studying compelling new data from the Mars Express spacecraft.
Take, for instance, the common perception that Mars' surface is old and dead.
Mars Express is obliterating that view with evidence of a planet dominated not by dust, wind and ancient craters, but by an ongoing war between volcanoes and glaciers.
It's also uncovering mineralogical signs that are making it much harder to argue that the Red Planet ever had large lakes or seas, and certainly not within the past 3.5 billion years.
"We may have to revise some of the previous views," says Mars Express investigator Professor Gerhard Neukum of Freie Universität in Berlin. "It wasn't so warm and not so wet in much of its time."
Signs of water
Among the evidence against Martian seas is the now-confirmed absence of any telltale spectral signatures of water-formed carbonates on Mars' surface.
Stranger, however, is the discovery that even in Mars' water-carved canyons there is no sign of water-made minerals, says Mars Express investigator Dr Jean-Pierre Bibring of the Institut d'Astrophysique Spatiale in Orsay, France.
Instead, such minerals as clays, which require water to form, are found on odd patches in the cratered landscape, where rocks from Mars' earliest history may be exposed, says Bibring.
More importantly, it's in those clays, which come from the only potentially Earth-like period of Mars' history, that we'd have the best chances of finding evidence of early Martian life, he says.
High-resolution stereo imaging by Mars Express has also revealed far more recently glaciated landscape and even what appears to be a lava flow that ends in long, abrupt wall.
The wall appears to be where the molten rock ran into now-evaporated glaciers just tens of millions of years ago, says Neukum.
Mars Express has also begun looking under the Martian surface with radar. Already, the ground-penetrating radar has revealed the first in what may be a hidden population of buried ancient craters, possibly soaked with frozen water.

A new study of gas in meteorites suggests Mars was bitterly cold for pretty much all of the past 4 billion years, putting the freeze on hopes that the Red Planet had any extended wet periods during which life could have flourished.
Several rocks that were once near the surface of Mars, and have in the past few million years been kicked up by impacts that sent them to Earth, have been freezing cold for most of the past 4 billion years, the study concludes.
While the findings don't rule out the possibility of life on Mars, they indicate that biology's best shot would have come in the first 500 million years of the Red Planet's 4.5-billion-year existence.
"Our research doesn't mean that there weren't pockets of isolated water in geothermal springs for long periods of time, but suggests instead that there haven't been large areas of free-standing water for 4 billion years," said David Schuster, a graduate student at the California Institute of Technology.
Shuster and Benjamin Weiss, an assistant professor at the Massachusetts Institute of Technology, present their results in Friday's issue of the journal Science.
Many scientists have tried to open ancient chapters in the book of Mars geology by modeling the past based on large channels carved into the dusty surface. In some scenarios — very popular a few years ago — the computers said Mars was warmer and wetter during much of its early time.
But recent evidence of past water, provided by the Mars rovers, has not revealed the sorts of huge and deep oceans that some might have hoped for. Instead, water might have existed in shallow lakes that did not necessarily last too long, providing only lukewarm support for the warmer and wetter theory.
Life as we know it requires liquid water, so much of the money spent to explore Mars is geared toward searching for signs of liquid water, past or present.
Yet scientists have failed to conclude whether the channels on Mars, some deeper and wider than any on Earth, were carved mostly by water or whether other substances — such as carbon dioxide — might have been involved. It is also not clear if the riverbeds were created gradually or, as many scientists have come to believe in recent years, by catastrophic floods of water and mud that came in short, hellish bursts.
"Our results seem to imply that surface features indicating the presence and flow of liquid water formed over relatively short time periods," Shuster said.

Moreover, Baker believes that there may be cold interludes within those brief warmer periods, and that Mars today may be in such a brief cold period.
"We don't know the answer to that yet -- that's very speculative," he said. "But if it's true, it would have major implications for sending people to Mars, because it may mean that water is more available than otherwise thought."
The warm periods are triggered, Baker believes, by a period of massive volcanic activity. The heat from that activity melts ice trapped below the surface, possibly enough to form a temporary ocean in the planet's northern region. A greenhouse effect created by carbon dioxide released into the atmosphere through the volcanic activity warms the atmosphere and allows water to remain in liquid form at the surface.
However, the warm, wet atmosphere eventually generates precipitation, which washes carbon dioxide out of the atmosphere. This cools the atmosphere again, freezing the water and eventually returning the planet to the cold, dry conditions that existed before the volcanic activity began.
While such conditions may seem harsh, Baker notes that it may still be hospitable to life. "This is the type of environment in which the extremophile progenitors of Earth's biosphere probably evolved," he said. "Indeed, early Mars provided an arguably better habitat for the inception and incubation of early life than did early Earth."

For more than two decades, the presence of an ancient Martian ocean has been a source of academic controversy. In recent years, radar and visual maps provided by orbiting space probes have strongly supported the existence of an ocean, billions of years ago. The European Space Agency’s “Mars Express” orbiter, for instance, detected probable ocean floor sediments in regions ringed by ancient Martian shorelines. Scientists at the University of Colorado at Boulder also mapped river deltas on the Martian service that apparently fed into vanished oceans. Now, planetary scientist Geronimo Villanueva and a team of researchers have published an article in the journal Science that provides compelling new evidence for a vast, long-lived Martian ocean. Their article has received major media attention, and, as of this writing, is on the front page of CNN.
Even without that breakthrough, human exploration and colonization of Mars will be influenced by the history of the planet’s atmosphere, hydrosphere, cryosphere, and perhaps biosphere. The presence of water on Mars will be essential for the survival of future colonists. The historical transformation of Mars from habitable world to frozen wasteland provides a window into what might have been on Earth, and that will encourage scientific missions. The Martian past might even provide a romantic stimulus for terraforming projects that aim to restore the planet to the liveable world it once was.
Note: I explore these ideas in greater detail in a journal article that I am preparing for submission.
Villanueva, G. L., M. J. Mumma, R. E. Novak, H. U. Käufl, P. Hartogh, T. Encrenaz, A. Tokunaga, A. Khayat, and M. D. Smith. "Strong water isotopic anomalies in the martian atmosphere: Probing current and ancient reservoirs." Science, 2015. DOI: 10.1126/science.aaa3630

When it arrived in November 1971, Mars was in the middle of one of its famous global dust storms. But when the storm cleared, Mariner 9’s cameras revealed volcanoes, canyons, flood features, dried-up riverbeds, layered sediments, and many landforms shaped by ground ice. The surface, it turned out, was much more geologically diverse than indicated by the earlier flybys. Mars had been active for much of its history, and water and climate change were implicated.
With each successive spacecraft mission, evidence for climate change accumulated. Many of the fluvial features discovered by Mariner 9 and mapped at higher resolution by subsequent missions are best explained by flowing liquid water in a warm climate. Furthermore, they are frequently found on surfaces that cratering statistics suggest date to the Noachian period between 4.1 and 3.7 billion years ago (Gya). Thus, billions of years ago, a warm, wet climate apparently existed on Mars. The hypothesis that emerged was that Mars had a thicker CO2 atmosphere then—one that was capable of providing a strong enough greenhouse effect to warm the surface to the melting point despite the faint young Sun (Pollack et al., 1987). Evidence also emerged for relatively recent climate change. Both polar regions on Mars are geologically young (<100 My) and consist of thick deposits of layered sedimentary material composed predominantly of water ice. These were interpreted as evidence for periodic climate change associated with variations in Mars’ orbit parameters (e.g., Pollack, 1979; Toon et al., 1980). Thus, there is evidence for two different types of climate change on Mars: one related to a change in the mass and composition of the atmosphere early in its history, and one related to changing orbital properties relatively late in its history. The connection between these two epochs implies that the atmosphere thinned over time and that the climate system was dominated by changes in radiative forcing. This picture remains the general consensus, although the details are still under debate.
The most important controls on a planet’s climate system are the mass1 and composition of its atmosphere, its orbital properties, and the luminosity of the star it orbits.

“The most difficult aspect is letting go of Earth and the bias that we have and really trying to get into the foundations of the chemistry, physics, and environmental processes on Mars,” said Goddard astrobiologist Jennifer L. Eigenbrode, who took part in the carbon research. Eigenbrode previously led an international team of Curiosity scientists in the discovery of a wide range of organic compounds on the Martian surface.
Eigenbrode said, “We need to broaden our thoughts and look beyond the box, and that is what this study accomplishes.”
In their report, the researchers suggest two non-biological reasons for the odd carbon signature. Molecular clouds are one of them.
Our Solar System went through a molecular cloud hundreds of millions of years ago, according to the molecular cloud theory. Although this is a rare occurrence, it occurs once per 100 million years, so scientists cannot rule it out.
Molecular clouds are typically made up of molecular hydrogen, but one in Gale Crater may have been particularly rich in the sort of lighter carbon found by Curiosity.
In this scenario, the cloud would have caused Mars to cool substantially, resulting in glaciers. Because of the cooling and glacial, the lighter carbon in the molecular clouds would not have mixed with the rest of Mars’ carbon, resulting in deposits of increased C12. “Glacial melt during the glacial epoch and ice retreat thereafter should leave interstellar dust particles on the glacial geomorphological surface,” according to the report.
Curiosity discovered some of the heightened C12 levels at the summits of ridges, such as the top of Vera Rubin Ridge, and other high spots in Gale Crater, which supports the concept. According to the article, the samples were collected from “a diversity of lithologies (mudstone, sand, and sandstone) and are temporally distributed across the mission activities to date.” Nonetheless, the molecular cloud idea is an improbable series of occurrences.
Ultraviolet light is the other non-biological idea. The atmosphere of Mars contains over 95% carbon dioxide, and UV radiation would have reacted with the carbon dioxide gas in the atmosphere to produce new carbon-containing molecules in this scenario.
The molecules would have showered down on Mars’ surface, becoming ingrained in the rock. This theory is comparable to how methanogens make C12 indirectly on Earth, except it is completely abiotic.
“All three interpretations suit the data,” said Christopher House, the study’s primary author.

- "Curiosity Mars rover detects 'useful nitrogen'". NASA. BBC News. 25 March 2015. Archived from the original on March 27, 2015. Retrieved 2015-03-25.
- Boxe, C. S.; Hand, K.P.; Nealson, K.H.; Yung, Y.L.; Saiz-Lopez, A. (2012). "An active nitrogen cycle on Mars sufficient to support a subsurface biosphere". International Journal of Astrobiology. 11 (2): 109–115. Bibcode:2012IJAsB..11..109B. doi:10.1017/S1473550411000401. Archived from the original on May 18, 2015. Retrieved 2015-05-10.
- Schuerger, Andrew C.; Ulrich, Richard; Berry, Bonnie J.; Nicholson, Wayne L. (February 2013). "Growth of Serratia liquefaciens under 7 mbar, 0°C, and CO2-Enriched Anoxic Atmospheres". Astrobiology. 13 (2): 115–131. Bibcode:2013AsBio..13..115S. doi:10.1089/ast.2011.0811. PMC . PMID 23289858.
- Heldmann, Jennifer L.; Toon, Owen B.; Pollard, Wayne H.; Mellon, Michael T.; Pitlick, John; McKay, Christopher P.; Andersen, Dale T. (2005). "Formation of Martian gullies by the action of liquid water flowing under current Martian environmental conditions". Journal of Geophysical Research. 110 (E5): E05004. Bibcode:2005JGRE..11005004H. doi:10.1029/2004JE002261.
- Kostama, V.-P.; Kreslavsky, M. A.; Head, J. W. (2006). "Recent high-latitude icy mantle in the northern plains of Mars: Characteristics and ages of emplacement". Geophysical Research Letters. 33 (11): 11201. Bibcode:2006GeoRL..3311201K. doi:10.1029/2006GL025946.

A number of scientists have suggested that a shallow ocean subsequently covered the lava-coated northern plains. However, no evidence in support of this is provided by the new results.
“Our studies do not find any signs of the lava plains in the north being altered by water,” says Dr Bibring.
On a positive note, the new results may suggest sites for future landers because evidence for water during the early history of Mars suggests that conditions may have been favourable for the evolution of primitive life.
“These results reveal the history of Mars derived from the planet’s mineralogy,” says Olivier Witasse, ESA Project Scientist for Mars Express. “It is another example of the fruitful cooperation between European and American scientists.”

Journal of Geophysical Research, 110(E12).
- Hu, R., Kass, D. M., Ehlmann, B., & Yung, Y. L. (2015). Tracing the fate of carbon and the atmospheric evolution of Mars. Nature Communications, 6, 10003.
- Ingersoll, A. P. (1970). Mars: Occurrence of liquid water. Science, 168, 972–973.
- Jakosky, B. M., Brain, D., Chaffin, M., Curry, S., Deighan, J., Grebowsky, J., Halekas, J., Leblanc, F., Lillis., R., Luhmann, J. G., Andersson, L., Andre, N., Andrews, D., Baird, D., Baker, D., Bell, J., Benna, M., Bhattacharyya, D., Bougher, S., Bowers, C., … Zurek, R. (2018). Loss of the Martian atmosphere to space: Present-day loss rates determined from MAVEN observations and integrated loss through time. Icarus, 315, 146–157.
- Kahre, M. A., Hollingsworth, J. L., Haberle, R. M., & Wilson, R. J. (2015). Coupling the Mars dust and water cycles: The importance of radiative-dynamic feedbacks during northern hemisphere summer. Icarus, 260, 477–480.
- Kahre, M. A., Murphy, J. R., Newman, C. E., Wilson, R. J., Cantor, B. A., Lemmon, M. T., & Wolff, M. J. (2017). The Mars dust cycle. In R. M. Haberle, R. T. Clancy, F. Forget, M. D. Smith, & R. W. Zurek (Eds.), The atmosphere and climate of Mars (pp. 295–337). Cambridge University Press.
- Kasting, J. F. (1991). CO2 condensation and the climate of early Mars. Icarus, 94, 1–13.
- Kerber, L., Forget, F., & Wordsworth, R. (2015).

It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
What some argue is evidence of ancient life in a meteorite from Mars could have a simple chemical explanation, scientists now suggest. These findings could also shed light on of the tricky chemistry going on in the atmospheres of both Mars and Earth.
Impacting space rocks on Mars over the years have hurled debris off the planet, some of which has landed on Earth. One such rock — the 3.9 billion-year-old meteorite known as ALH84001 — had globular, micron-sized carbonate particles seemingly arranged in chains that some thought must have been made by ancient Martian life. However, researchers have now discovered a new way to form carbonates on Earth without interference from biological organisms. They suggest this process likely takes place on Mars as well.
Unusual oxygen type: The carbonates seen in ALH84001 possessed unusually high levels of the isotope oxygen-17. (An oxygen atom has eight protons in its nucleus, and while most of these also have eight neutrons, oxygen-17 has nine.) Atmospheric chemist Robina Shaheen at the University of California at San Diego discovered anomalously high levels of oxygen-17 in carbonates found on dust grains, aerosols and dirt on Earth as well. This hinted that a chemical process common to both planets might be at work.
I don't. I was alive in 1996 when they made the initial announcement which said:
Originally posted by anon72
Now, most of us will remember the ground breaking news of 2007 (I think) of LIFE ON MARS-Proof.
So, it says "inorganic formation is possible"!!
The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features, including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota.
I'm skeptical of some science too, however the far bigger problem we need to be skeptical of, are media reports which distort what the scientists actually say.

(2010). Lakes on Mars. Elsevier.
- Carr, M., & Head, J. (2019). Mars: Formation and fate of a frozen Hesperian ocean. Icarus, 319, 433–443.
- Carr, M. H. (1979). Formation of Martian flood features by release of water from confined aquifers. Journal of Geophysical Research, 84, 2995–3007.
- Carr, M. H. (1981). The surface of Mars. Yale University Press.
- Carr, M. H. (1992). Post-Noachian erosion rates: Implications for Mars climate change. In 23rd Lunar and Planetary Science Conference (Vol. 23, pp. 205–206). Lunar and Planetary Science Institute.
- Carr, M. H., & Head, J. W. (2010). Geological history of Mars. Earth and Planetary Science Letters, 294, 185–203.
- Cassata, W. S., Shuster, D. L., Renne, P. R., & Weiss, B. P. (2012). Trapped Ar isotopes in meteorite ALH 84001 indicate Mars did not have a thick ancient atmosphere. Icarus, 221, 461–465.
- Chassefière, E., Langlais, B., Quesnet, Y., & Leblanc, F. (2013). The fate of early Mars’ lost water: The role of serpentinization. Journal of Geophysical Research: Planets, 117, 1123–1134.
- Clifford, S. M., & Parker, T. J. (2001). Evolution of the Martian hydrosphere: Implications for the fate of a primordial ocean and the current state of the northern plains. Icarus, 154, 40–79.
- Craddock, R. A., & Greeley, R. (2009). Minimum estimates of the amount and timing of gases released into the Martian atmosphere from volcanic eruptions. Icarus, 204, 512–526.
- Craddock, R. A., & Howard, A. D. (2002).

New evidence suggests that Mars' dry climate was once wetter and possibly more Earth-like. The European Space Agency (ESA) has released images of two side-by-side craters offering clues to the dusty, barren Red Planet's past. Here's what you should know about the new theory:
What exactly do the photographs depict?
The high-resolution stereo images showcase the Danielson and Kalocsa craters, which sit side by side in a desert-like region called Arabia Terra. Snapped on June 19, 2011, from aboard the Mars Express spacecraft, the photos highlight new topographical evidence that has led experts to posit that the larger crater was once filled with water.
What's the evidence?
In the much bigger, 38-mile-across Danielson crater — named after George E. Danielson, who pioneered many of the cameras used to photograph Mars today — steep, wind-carved hills called "yardangs," characterized by distinct layers of sediment, protrude from the crater's bottom. (See a photo below.) ESA scientists believe the sediment that forms these yardangs was deposited there by strong north-northeasterly winds and then hardened (or cemented) by water, "possibly from an ancient deep groundwater reservoir," says Alan Boyle at MSNBC. In contrast, the more elevated, 20-mile-wide Kalosca crater features a smooth bottom with no such structures jutting out, possibly because it was never deep enough to reach the groundwater.
What happened to the water?
The theory is that slight shifts in the planet's axis triggered drastic climate changes over millions of years, leading to intermittent wet and dry periods. Judging from the yardangs' orientation, researchers believe that the same strong north-northeasterly winds that deposited the original sediments battered them with dust and sand during a dry spell after the water disappeared, carving the yardangs into their characteristic shapes. Similar axis changes are thought to have wrought the extreme ice age cycles here on Earth. Take a look at the yardangs in the Danielson crater:

Martian Greenhouse: Volcanic CO2 Doesn’t Cut It
With all the evidence for water on the surface of Mars in the distant past, we always return to the same question: how was it possible for water to be stable back then? These days any liquid water on the surface would boil due to the low pressure or freeze due to the low temperature (or maybe do both at the same time!).
To explain liquid water on the past, there has been a lot of work done to see whether a thicker atmosphere of CO2 could provide high enough pressure and temperature to allow stable water. Today Marc Hirschmann gave an interesting talk about whether volcanoes could give off enough gas to do the job.
It turns out that since the sun was dimmer in the past, and since Mars is farther from the sun than the Earth, the early CO2 atmosphere of mars would have to be several times as thick as Earth’s current atmosphere to keep liquid water stable at the surface. Hirscmann estimated how much volcanism there was on Mars based on the heat flow from the planet, and then calculated the amount of CO2 released based on the amount of carbon in the mantle. Hirschmann showed that on Mars, with the amount of oxygen available to react with rocks (the so-called “oxygen fugacity”), the carbon in many lavas would likely be in the form of graphite, or even diamonds deep in the mantle where the pressure is higher.
With reasonable estimates of the amount of volcanism and the amount of carbon in the lavas, Hirschmann estimated that even in the “best case” scenario, volcanism can only provide an atmosphere with 0.1 bars of CO2: only a tenth of Earth’s atmospheric pressure and not nearly enough to make Mars warm. This led Hirschmann to look at the possibility of CO2 from the formation and stabilization of the crust. Depending on the assumptions you make, this process can give either 10s of bars of CO2, or a negligible amount.
Hirschmann concluded that if crust formation was the source of a thick atmosphere, it would require the most extreme limits of likely conditions. Alternatively, a CO2 atmosphere could have somehow persisted from the very earliest period of martian evolution, when the planet had a “magma ocean”. Alternatively, there may have been a greenhouse effect caused by something other than CO2, such as SO2 or methane.

Imaginative, but lovely
If you've ever wondered what Mars might have looked like in the distant past when it had oceans and a cloud-filled atmosphere, an enterprising geek and digital artist from Nashua, NH, can help. But before we inspect the results of the imaginative Kevin Gill's combination of programming chops and artistic skills, let's take a …
Imaginative, but lovely
Obviously you have not seen the US documentary "Total Recall", where historian Arnold Schwarzenegger clearly demonstrates that not only did life on Mars exist, but if you flip the big switch the atmostphere and water will return.
Not pure speculation. There are several theories addressing the origins and development of life on planets like ours and some do involve (ongoing) exchanges with neighboring planets or being at the receiving end of the same common mechanism. So instead of speculation it's a falsifiable claim backed up by theory and therefore a serious hypothesis and not just speculation.
Pure speculation. True (at present)
Surface water existed on Mars (at some point). Fact.
Life existed on Mars (in the past) possible.
What has not changed is Martian gravity (roughly 1/3 g). and the level of Sunlight it has gotten.
I'd suggest that they would have a major impact on what atmospheric pressure can be retained (and hence things like the boiling point of water) and temperature.
Start with an arbitrary air pressure and see how if it's retained or decays over time (and if so what to).
Saying life may have existed on mars at some point in the past is misleading. It gives far more credence to the idea than is warranted by the data.
How many of the life millions of forms that we know of could survive there if transplanted there?
Which of the mechanisms for the generation of life from inorganic materials that we have observed on earth have we observed evidence for on mars?
He said "it's possible". Who would have though it's possible for organisms to live at Challenger Deep, 36,000 ft below the oceans surface, where there's zero light and the water pressure is the equivalent of having about 50 jumbo jets piled on top of you. Or bacteria living in Antarctic lakes that have been covered by ice for thousands of years. Yet they do.

How thick is uncertain, but estimates based on the observed crater size distribution (Kite et al., 2014), isotopic modeling (Kurokawa et al., 2018), the 40Ar/36Ar ratio in ALH84001 (Cassata et al., 2012), lava flow volumes (Craddock & Greeley, 2009; Phillips et al., 2001), atmospheric escape (Hu et al., 2015), and magma composition (Lammer et al., 2013) suggest that the Noachian atmosphere was likely composed primarily of CO2, having surface pressures between ~0.5 and 2 bars. It is worth noting that above ~2 bars, CO2 begins to condense in a pure CO2 atmosphere (e.g., Forget et al., 2013; Kasting, 1991), which limits its abundance in the atmosphere; above ~3 bars, permanent CO2 ice caps form and surface pressures are buffered by their heat balance.
The main challenge for this period of Martian history, however, is finding an explanation for the comparatively high erosion rates and fluvio-lacustrine features. Rainfall and runoff in a warm early climate are an obvious explanation, but the circumstances producing such conditions are in dispute. The main problem is overcoming the faint young Sun, which was ~30% less luminous during the Noachian. An atmosphere producing a strong greenhouse effect can overcome the faint young Sun problem, but it must have enough greenhouse power to raise the surface temperature 77 K above the effective temperature to reach the melting point of water (Haberle, 1998). Considering that Earth’s atmosphere, whose greenhouse is powered by CO2 and water, provides 33 K of greenhouse warming, reaching the 77 K mark is clearly a challenge. Complicating matters further, Mars climate models cannot produce such a strong greenhouse effect for atmospheres consisting of CO2 and water alone (e.g., Forget et al., 2013; Wordsworth et al., 2013).
One way to overcome this problem is with supplemental greenhouse gases. Gases such as SO2, NH3, and CH4 are good greenhouse gases, but raising and sustaining their concentrations to the required amounts is problematic given plausible estimates of their sources and sinks.

How much manganese oxide was detected and what is the meaning?
“The Curiosity rover observed high-Mn abundances (>25 wt% MnO) in fracture-filling materials that crosscut sandstones in the Kimberley region of Gale crater, Mars,” according to the AGU paper.
“On Earth, environments that concentrate Mn and deposit Mn minerals require water and highly oxidizing conditions, hence these findings suggest that similar processes occurred on Mars.”
“Based on the strong association between Mn-oxide deposition and evolving atmospheric dioxygen levels on Earth, the presence of these Mn-phases on Mars suggests that there was more abundant molecular oxygen within the atmosphere and some groundwaters of ancient Mars than in the present day.”
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Curiosity, Curiosity Rover, Featured, Gale crater, Jet Propulsion Laboratory (JPL), JPL, manganese oxide minerals, Mars, mars red planet, Mars Science Laboratory (MSL), Mars Science Laboratory (MSL) Curiosity Rover, MSL, NASA, Search for Life, The Kimberley waypoint, windjana

The mineralogical evidence is mounting that early Mars had a significant amount of liquid water on its surface, though exactly how long it remained is unclear.
The highest-resolution spectrometry ever taken from orbit shows both a greater variety and a greater abundance of clay minerals – which formed in the presence of water – than previously detected in the planet’s oldest terrain. Researchers say any life the planet may have hosted may be preserved in the clays, making them good targets for future rovers.
Since the 1970s, spacecraft have beamed back images of deep channels and canyons that suggest water once flowed across the Red Planet. But researchers have only recently begun to find the mineralogical signature of that water.
That’s because the spectrometers on previous spacecraft have operated at relatively long wavelengths and low spatial resolutions, parameters best-suited to mapping the basaltic materials and dust that dominate the planet’s surface.
The first high-resolution data was taken by an instrument called OMEGA on Europe’s Mars Express spacecraft, which went into orbit around the planet in 2003. In 2006, researchers using OMEGA found clays , or phyllosilicates, in about two dozen sites scattered around the planet, all in terrain estimated to date from the planet’s first 500 million years.
Still, OMEGA could only resolve sections of the surface as wide as a few hundred metres. Sections as small as 18 metres across can now be resolved with an instrument called CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) on NASA’s Mars Reconnaissance Orbiter, which began orbiting the planet in March 2006.
“We can really see individual outcrops of rocks,” says Ralph Milliken of NASA’s Jet Propulsion Laboratory in Pasadena, California. He is a member of a team led by John Mustard of Brown University in Providence, Rhode Island, that studied the CRISM data.
‘Quite a bit of water’
CRISM has mapped a bit more than half the planet’s surface at a resolution of about 100 metres, focusing in on some areas at even higher resolutions.
“We’ve seen a lot more hydrated minerals, and a lot more occurrences of them” than observed with OMEGA, Milliken told New Scientist.

Scientists have learned a lot about Mars in recent years, and based on observations from the fancy hardware NASA has sent to the Red Planet we know that it once held far more water than we see today. But knowing there was lots of water (or at least abundant ice) on Mars long ago doesn’t necessarily tell us what the climate was like.
Without a time machine, we can’t know exactly what ancient Mars looked like, but researchers have come up with a pretty solid guess. Using data from NASA’s CRISM spectrometer and the Curiosity rover, scientists have a good idea of what kinds of minerals are present in the Martian soil. Using various areas of Earth as analogs, they can observe the conditions that caused similar mineral deposition patterns on our planet and assume that similar climates were responsible for their formation on Mars as well.
At the Goldschmidt Geochemistry Conference in Barcelona this week, Purdue University professor Briony Horgan announced the findings of a new research effort that draws comparisons between the climate of present-day Earth with that of ancient Mars.
“Our study of weathering in radically different climate conditions such as the Oregon Cascades, Hawaii, Iceland, and other places on Earth, can show us how climate affects pattern of mineral deposition, like we see on Mars,” Horgan said. “This leads us to believe that on Mars 3 to 4 billion years ago, we had a general slow trend from warm to cold, with periods of thawing and freezing.”
The study dives deep into the nuances of various mineral deposits such as silica, which the scientists believe hints at melting ice. This suggests that the planet had some ups and downs with regard to temperature, with warm periods characterized by occasional rains and then colder periods where everything was frozen.
Mars today is frigid compared to Earth, and that’s largely owed to the fact that the planet’s atmosphere has been almost entirely stripped away. Billions of years ago, the planet is thought to have had a much more robust atmosphere which would have aided in it retaining heat. A temperate climate with rain and flowing water certainly sounds like a recipe for life as we know it, but we may have to wait and see what the Mars 2020 rover has to say about that once it arrives in early 2021.

- McEwen, Alfred S.; Ojha, Lujendra; Dundas, Colin M.; Mattson, Sarah S.; Byrne, Shane; Wray, James J.; Cull, Selby C.; Murchie, Scott L.; et al. (2011). "Seasonal Flows on Warm Martian Slopes". Science. 333 (6043): 740–3. Bibcode:2011Sci...333..740M. doi:10.1126/science.1204816. PMID 21817049.
- "Mars Rover Spirit Unearths Surprise Evidence of Wetter Past" (Press release). Jet Propulsion Laboratory. May 21, 2007. Archived from the original on May 24, 2007.
- "Mars Rover Investigates Signs of Steamy Martian Past" (Press release). Jet Propulsion Laboratory. December 10, 2007. Archived from the original on December 13, 2007.
- Leveille, R. J. (2010). "Mineralized iron oxidizing bacteria from hydrothermal vents: Targeting biosignatures on Mars". American Geophysical Union. 12: 07. Bibcode:2010AGUFM.P12A..07L.
- Walter, M. R.; Des Marais, David J. (1993). "Preservation of Biological Information in Thermal Spring Deposits: Developing a Strategy for the Search for Fossil Life on Mars". Icarus. 101 (1): 129–43. Bibcode:1993Icar..101..129W. doi:10.1006/icar.1993.1011. PMID 11536937.
- Allen, Carlton C.; Albert, Fred G.; Chafetz, Henry S.; Combie, Joan; Graham, Catherine R.; Kieft, Thomas L.; Kivett, Steven J.; McKay, David S.; et al. (2000). "Microscopic Physical Biomarkers in Carbonate Hot Springs: Implications in the Search for Life on Mars". Icarus. 147 (1): 49–67. Bibcode:2000Icar..147...49A. doi:10.1006/icar.2000.6435.

astroengine writes: At one time, Mars had a thick, protective atmosphere — possibly even cushier than Earth’s — but the bubble of gases mostly dissipated about 4 billion years ago and has never been replenished, new research shows. The findings come from NASA’s Mars rover Curiosity, which has been moonlighting as an atmospheric probe as it scours planet’s surface for habitats that could have supported ancient microbial life. “On Earth, our magnetic field protects us, it shields us from the solar wind particles. Without Earth’s magnetic field, we would have no atmosphere and there would be no life on this planet. Everything would be wiped out — especially when you go back 4 billion years. The solar wind was at least 100 times stronger then than it is today. It was a young sun with a very intense radiation, ” Chris Webster, manager of the Planetary Sciences Instruments Office at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News. Unfortunately for Mars, the last 4 billion years have not been kind.
DEAL: For $25 - Add A Second Phone Number To Your Smartphone for life! Use promo code SLASHDOT25. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. Check out the new SourceForge HTML5 internet speed test! ×

Journal of Geophysical Research. 109. Bibcode:2004JGRE..10909006F. doi:10.1029/2003JE002160.
- "Mars Global Surveyor Measures Water Clouds". Archived from the original on August 12, 2009. Retrieved 2009-03-07.
- Baker, V. R.; Strom, R. G.; Gulick, V. C.; Kargel, J. S.; Komatsu, G.; Kale, V. S. (1991). "Ancient oceans, ice sheets and the hydrological cycle on Mars". Nature. 352 (6336): 589–594. Bibcode:1991Natur.352..589B. doi:10.1038/352589a0.
- "Flashback: Water on Mars Announced 10 Years Ago". SPACE.com. June 22, 2000. Archived from the original on December 22, 2010.
- "The Case of the Missing Mars Water". Science@NASA. Archived from the original on March 27, 2009. Retrieved 2009-03-07.
- "Mars Rover Opportunity Examines Clay Clues in Rock". NASA. Jet Propulsion Laboratory. May 17, 2013. Archived from the original on June 11, 2013.
- "NASA Rover Helps Reveal Possible Secrets of Martian Life". NASA. November 29, 2005. Archived from the original on November 22, 2013.
- ISBN 0-312-24551-3[page needed][full citation needed]
- "PSRD: Ancient Floodwaters and Seas on Mars". Psrd.hawaii.edu. July 16, 2003. Archived from the original on January 4, 2011.
- "Gamma-Ray Evidence Suggests Ancient Mars Had Oceans". SpaceRef. November 17, 2008.
- Carr, Michael H.; Head, James W. (2003). "Oceans on Mars: An assessment of the observational evidence and possible fate". Journal of Geophysical Research: Planets. 108: 5042. Bibcode:2003JGRE..108.5042C.

Most encouraging were a discovery by the orbiter science team that the permanent polar caps are made of water, and a finding, made during lander entry, that nitrogen, considered essential to life on Earth, is present in the atmosphere of Mars. Analysis of argon isotope ratios in the atmosphere indicated that Mars, at some time in the past, had a warmer climate and thicker atmosphere than at present. On the negative side, water is present but scarce, and the Mars of the past, according to admittedly tentative attempts by planetologists to reconstruct its history, may have been only marginally more hospitable than the Mars of today. Nitrous oxide – laughing gas – was found in the Martian atmosphere, and Earth’s nitrous oxide is produced by living creatures, but there are other ways to produce nitrous oxide, and its presence is not considered evidence of life on Mars. The modern climate is harsh. During the six months of summer (the Martian year, and therefore its seasons, are twice as long as Earth’s) temperatures seldom exceed 20° Fahrenheit below zero, and at night typically drop to 150° below zero. Atmospheric pressure at the lander sites is only seven or eight millibars, or about that of Earth at an altitude of some 20 miles. If there is life on Mars, it is a tough life.
Earth organisms can be found living happily in boiling sulfur springs and at the floor of the ocean under enormous pressures. Spores blown into Antarctic valleys – the regions Wolf Vishniac was exploring when he died – hibernate successfully for centuries in temperatures that never rise as high as the freezing point of water. So life is tenacious, and probably could survive on Mars. The question is, did life get started there?
Viking was conceived and presented to the public as an attempt to answer that question, but little was done to convey to the public the audacity of the assignment. Science at its present stage of development does not know how life began on Earth, let alone on Mars: only a few of the steps by which biology may have arisen from primordial seas have been reconstructed. Just over a century has passed since Darwin discovered the nature of evolution, less than a generation since Watson and Crick decoded the molecular basis of life, and even so straight forward a matter as satisfactorily defining life remains for the future.

Mars was a warm, wet planet that was likely capable of supporting life billions of years ago. Something caused the planet to lose its atmosphere and turn into the harsh, frozen desert it is today.
The Curiosity rover, which landed on Mars in 2012, has been exploring different aspects of Gale Crater on Mars to understand more about this transition from warm and wet to dry and very cold.
The latest study, gathered from data captured by one of the rover’s instruments, suggests that Mars actually transitioned back and forth between wetter and drier times before losing its surface water completely around three billion years ago.
Curiosity has been steadily climbing the 3-mile-high Mount Sharp, located at the center of Gale Crater, since 2014.
An instrument called a ChemCam sits on the rover’s mast and includes a high-resolution camera and laser that can vaporize rocks to help the rover analyze their chemical composition. ChemCam has an infrared-colored laser that can heat rock pieces to 18,000 degrees Fahrenheit. This vaporizes the rock and creates plasma, allowing scientists to essentially look inside the minerals and chemicals comprising the rock and peer back into the planet’s geologic history.
The camera on ChemCam was used for capturing observations of Mount Sharp’s terrain, which reveals slices of the Martian past as the rock varies.
A Mars history lesson
Mount Sharp is an intriguing feature on Mars because it’s one of the best ways the red planet recorded the history of its climate, water and sediment.
“A primary goal of the Curiosity mission was to study the transition between the habitable environment of the past, to the dry and cold climate that Mars has now. These rock layers recorded that change in great detail,” said Roger Wiens, study co-author on the paper and ChemCam team scientist at Los Alamos National Laboratory, in a statement.
The study published last week in the journal Geology.
Orbiters around Mars have previously recorded information about the minerals within Mount Sharp’s slopes. Curiosity’s data has provided even more detailed observations from the layers of sedimentary rocks and revealed dry and wet periods across the planet’s past.
Curiosity detects big changes in layers
As Curiosity has ascended Mount Sharp, the layers have changed dramatically.
The base of Mount Sharp is made of clay deposited by the lake that once filled the crater. Above that are layers of sandstone that still preserve evidence of how they were formed by wind-shaped dunes during drier times.

Fate of outflow channel effluents in the northern lowlands of Mars: The Vastitas Borealis Formation as a sublimation residue form frozen, ponded bodies of water. Journal of Geophysical Research, 4, 1–25.
- Kuhn, W. R., & Atreya, S. K. (1979). Ammonia photolysis and the greenhouse effect in the primordial atmosphere of the Earth. Icarus, 37, 207–213.
- Kurokawa, H., Kurosawa, K., & Usui, T. (2018). A lower limit of atmospheric pressure on early Mars inferred from nitrogen and argon isotopic compositions. Icarus, 299, 443–459.
- Lammer, H., Chassefiere, E., Karatekin, O., Morschhauser, A., Niles, P. B., Mousis, O., Odert, P., Möstl, U. V., Breuer, D., Dehant, V., Grott, M., Gröller, H., Hauber, E., & Pham, L. B. S. (2013). Outgassing history and escape of the Martian atmosphere and water inventory. Space Science Reviews, 174, 113–154.
- Laskar, J., Correia, A. C. M., Gastineau, M., Joutel, F., Levrard, B., & Robutel, P. (2004). Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus, 170, 343–364.
- Laskar, J. Levrard, B., & Mustard, J. F. (2002). Orbital forcing of the Martian polar layered deposits. Nature, 419, 375–377.
- Lee, D. C., & Halliday, A. N. (1997). Core formation on Mars and differentiaed asteroids. Nature, 388, 854–857.
- Leighton, R. B., & Murray, B. C. (1966). Behavior of carbon dioxide and other volatiles on Mars. Science, 153, 136–144.

And that has really been the premise of why scientists have been so hot and heavy on studying Mars, to find out next habitable planet when we toast our current one with Global Warming and pollution like we have been for decades. So far from this data Mars is looking like the next eligible bachelor for us to relocate to.
Villanueva`s research team exploited the chemistry of water molecules to trace the history of water on Mars back through time. The water molecules make-up equal two parts hydrogen and one part oxygen and the hydrogen part of the water molecule can also come in another form known as a heavy isotope which is called deuterium that is made up of a neutron in its nucleus which is different than the regular single proton most normal hydrogen atoms have.
The reasoning behind this is that when water molecules contain deuterium and are referred to as heavy or partially heavy water, regular water can be stripped from the atmosphere of Mars and lost into space much more easily.
Villanueva went on to add more insight on this by saying, "Over a long time, the lighter form [of water] will escape preferentially relative to the heavy form"
Over billions of years, this preferential water loss has left Mars enriched in semi-heavy water compared to regular water by a factor of seven times greater than the ratio in Earth`s water. Extrapolating backward from the current ratio of "normal" hydrogen to deuterium, and incorporating factors such as collisions between water molecules and the predominant molecule in Mars` atmosphere, carbon dioxide, Villanueva`s team were able to calculate how much water Mars has lost. (Cooper, K., Astrology Magazine)
Scientists are still speculating that there is still water on Mars which is locked up in its polar caps. And they are saying if you took the amount of water on Mars today it would more than likely equal an ocean around sixty-nine feet deep.
From the earlier number of there was supposedly once an ocean one-mile deep on the surface of Mars and now today it only has around an ocean of sixty-nine feet deep left on it, we can see the significant water loss over time which equals more than all the water in the Earths Artic Ocean.
Robin Wordsworth who is a planetary scientist at the Harvard School of Engineering and Applied Sciences who was not involved in the study commented, "Their [Villanueva et al.`s] results are entirely consistent with a predominantly cold, icy scenario for early Mars," said Wordsworth.

In R. M. Haberle, R. T. Clancy, F. Forget, M. D. Smith, & R. W. Zurek (Eds.), The atmosphere and climate of Mars (pp. 338–373). Cambridge University Press.
- Moore, J. M., Howard, A. D., Dietrich, W. E., & Schenk, P. M. (2003). Martian layered fluvial deposits: Implications for Noachian climate scenarios. Geophysical Research Letters, 30.
- Mustard, J. F., Cooper, C. D., & Rifkin, M. K. (2001). Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice. Nature, 412, 411–414.
- Newman, C. E., Lewis, S. R., & Read, P. L. (2005). The atmospheric circulation and dust activity at different orbital epochs on Mars. Icarus, 174, 135–160.
- Olsen, A. A., & Rimstidt, J. D. (2007). Using a mineral lifetime diagram to evaluate the persistence of olivine on Mars. American Mineralogist, 92, 598–602.
- Palucis, M. C., Dietrich, W. E., Williams, R. M. E., Hayes, A. G., Parker, T., Sumner, D. Y., Mangold, N., Lewis, K., & Newsom, H. (2016). Sequence and relative timing of large lakes in Gale crater (Mars) after the formation of Mount Sharp. Journal of Geophysical Research: Planets, 121, 472–496.
- Phillips, R. J., Davis, B. J., Tanaka, K. L., Byrne, S., Mellon, M. T., Putzig, N. E., Haberle, R. M., Kahre, M. A., Campbell, B. A., Carter, L. M., Smith, I. B., Holt, J. W., Smrekar, S. E., Nunes, D. C., Plaut, J. J., Egan, A. F., Titus, T. N., & Seu, R. (2011).

- Solomon, S. C., Aharonson, O., Aurnou, J. M., Banerdt, W. B., Carr, M. H., Dombard, A. J., Frey, H. V., Golombek, M. P., Hauck, S. A., II, & Zuber, M. T. (2005). New perspectives on ancient Mars. Science, 307, 1214–1220.
- Steakley, K., Murphy, J., Kahre, M., Haberle, R., & Kling, A. (2019). Testing the impact heating hypothesis for early Mars with a 3-D global climate model[https://doi.org/10.1016/j.icarus.2019.04.005], Icarus, 330, 169–188.
- Tarnas, J. D., Mustard, J. F., Lollar, B. S., Bramble, M. S., Cannon, K. M., Palumbo, A. M., & Plesa, A.-C. (2018). Radiolytic H2 production on Noachian Mars: Implications for habitability and atmospheric warming. Earth and Planetary Science Letters, 502, 133–145.
- Tera, F., Papanastassiou, F. A., & Wasserburg, G. J. (1974). Isotopic evidence for a terminal lunar cataclysm. Earth and Planetary Science Letters, 22, 1–22.
- Tian, F., Kasting, J. F., & Solomon, S. C. (2009). Thermal escape of carbon from the early Martian atmosphere. Geophysical Research Letters, 36.
- Toon, O. B., Pollack, J. B., Ward, W., & Bilski, K. (1980). The astronomical theory of climatic change on Mars. Icarus, 44, 552–607.
- Turbet, M., Boulet, C., & Karman, T. (2020). Measurements and semi-empirical calculations of CO2 + CH4 and CO2 + H2 collision-induced absorption across a wide range of wavelengths and temperatures: Application for the prediction of early Mars surface temperature. Icarus, 346, 113762.

"A global depth of 137 meters still implies a relatively dry planet, and doesn`t allow a deep northern ocean. The water could have mainly been in the form of ice rather than liquid." (Woodsworth, R.)
The results according to Wordsworth would indicate that Mars is not really a very habitable planet. If the comments and data by Wordsworth are correct then all the hype and excitement about Mars being our next planet we could relocate to because it is supposedly habitable would shoot down that theory.
Like anything though the study is ongoing and new data and information are constantly being revealed like an up and down roller coaster about Mars which changes current hypothesis about the Red planet so it is going to take a lot more time and study to get to the real answers about Mars
According to Bethany Ehlmann of the California Institute of Technology in Pasadena, the evidence for a northern ocean is scant. (Cooper, K.)
Bethany Ehlmann went on to further comment on this, "An ocean is an intriguing possibility but mineralogical evidence, such as carbonates or evaporates, which are typical of evidence for Earth`s large ocean basins, has not been found in the north, although researchers are still looking." (Ehlmann, B.)
So, the question if water ever existed on Mars is ongoing but Geronimo Villanueva still remains optimistic about this and went on to say, "It is difficult to assess the temperature of ancient Mars, and for how long water was in liquid form, from our results but our results do indicate that a substantial amount of water was available in the past."
Scientists and NASA continue researching every square inch on Mars for the evidence that water did really exist. NASA`s MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft is currently in orbit studying and investigating the atmosphere of Mars and will explore new ventures to try to find firm evidence of the existence of water.
Villanueva went on to comment, "We still don`t know how the molecules are escaping more sophisticated measurements are going to give us a much better idea of how and when the molecules escaped from Mars."
So, Mars continues to live up to its reputation of being the red headed step child of the planets in our solar system. It continues to reveal new and interesting information that blows away scientists and conflicting information that baffle scientists.

In order for the lake to have been sustained for millions of years, the planet must have had a vigorous hydrological cycle, probably involving rains or snows, to keep the atmosphere humid enough. This challenges the widely held notion that Mars’ early climate was only wet during short periods after volcanic activity or space rock impacts. Furthermore, the findings could even suggest that the planet once featured a surface ocean, which would have prevented the lake from evaporating.
Scientists also thought that, alongside water, Gale could have had the “right ingredients and environment to have been able to support microbial life,” said Michael Meyer, lead scientist of the Mars Exploration Program. But they didn’t know whether the conditions lingered long enough for life to form; now, tantalizingly, it seems that water may have persisted long enough for this to be a possibility.

And from Mars it's just a short hop to Ice Age Earth...
Written by Andy Lloyd, 22nd March 2015
1) Malin, M. C., and K. S. Edgett "Evidence for recent groundwater seepage and surface runoff on Mars", Science, 288: 5475, 2330–2335, 30 June 2000
2) James Dickson et al "Recent climate cycles on Mars: Stratigraphic relationships between multiple generations of gullies and the latitude dependent mantle", Icarus, 252: 83-94, 15 May 2015
3) Elizabeth Howell "Could water have carved channels on Mars half a million years ago?" 19 March 2015, with thanks to Jim
4) A. Johnsson, D. Reiss, E. Hauber, H. Hiesinger, M. Zanetti. "Evidence for very recent melt-water and debris flow activity in gullies in a young mid-latitude crater on Mars", Icarus, 235: 37, June 2014
5) A. Lloyd "A Martian Riddle" 22 September 2014
Dark Star Blog 18
6) 2) Lisa Grossman "
8) James Dickson et al "Formation of Gullies on Mars by Water at High Obliquity: Quantitative Integration of Global Climate Models and Gully Distribution" 46th Lunar and Planetary Science Conference, 2015
9) Bruce Moomaw Cameron Park "The Obliquity of Mars" 30 June 2000
10) Lori Stiles "The Ancient Oceans of Mars: Gamma-Ray Evidence Suggests Ancient Mars Had Oceans" 17 November 2008
11) Ian Sample "Curiosity rover's discovery of methane ‘spikes’ fuels speculation of life on Mars" 17 December 2014
12) Touma, J. & Wisdom, J. "The Chaotic Obliquity of Mars", Science, 259 (5099): 1294–1297, 1993
13) MSSS "Cydonia: Two Years Later" 5 April 2000
14) DLR News "The Cydonia Region – was the North of Mars Once Covered by an Ocean?" 12 March 2015 with thanks to Jim.

The fate of water on Mars has been hotly debated by scientists because the planet is currently dry and cold, in contrast to the widespread fluvial features that carve much of the planet’s surface. Scientists believe that if water did once flow on the surface of Mars, the planet’s bedrock should be full of carbonates and clays. Such minerals could provide further evidence that Mars once hosted habitable environments with liquid water. Researchers have struggled to find physical evidence for carbonate-rich bedrock, which may have formed when paleoatmospheric carbon dioxide was trapped in ancient surface waters.
A new study by Wray et al. provides evidence for widespread buried deposits of Fe- and Ca-rich carbonates on Mars. The researchers, supported by the SETI Institute NASA Astrobiology Institute (NAI) team, identified carbonates on the planet using data from CRISM and HiRISE on the Mars Reconnaissance Orbiter.
“Outcrops in the 450-km wide Huygens basin contain both iron- and calcium-rich carbonate-bearing rocks” according to study lead Dr. James Wray of Georgia Tech and NAI team Co-Investigator. The Huygens basin is an ideal site to investigate carbonates because multiple impact craters and troughs expose ancient, subsurface materials where carbonates are detected across a broad region. The study highlights evidence of carbonate-bearing rocks in multiple sites across the Red Planet, including Lucaya crater, where the ancient 3.8 Ga year old carbonates and clays were buried by as much as 5 km of lava and caprock. Study co-author Dr. Janice Bishop of the SETI Institute and also a NAI Co-Investigator says that “identification of these ancient carbonates and clays on Mars represents a window into the past when the climate on Mars was very different from the cold and dry desert of today”. The extent of the global distribution of Martian carbonates is not yet resolved and the early climate on Mars remains under debate. However, this study moves us forward in our understanding of potential Martian habitability.
Aeolian bed forms overlie ancient layered, ridged carbonate-rich outcrop exposed in the central pit of Lucaya crater, northwest Huygens basin, Mars. The image was taken by the High Resolution Imaging Science Experiment (HiRISE) instrument aboard the Mars Reconnaissance Orbiter. Credit: NASA/JPL/University of Arizona.

The ClO3− suggests presence of other highly oxidizing oxychlorines such as ClO2− or ClO, produced both by UV oxidation of Cl and X-ray radiolysis of ClO4−. Thus only highly refractory and/or well-protected (sub-surface) organics are likely to survive. In addition, recent analysis of the Phoenix WCL showed that the Ca(ClO4)2 in the Phoenix soil has not interacted with liquid water of any form, perhaps for as long as 600 Myr. If it had, the highly soluble Ca(ClO4)2 in contact with liquid water would have formed only CaSO4. This suggests a severely arid environment, with minimal or no liquid water interaction.
Mars Science Laboratory[edit | hide | edit source]
The Mars Science Laboratory mission is a NASA project that launched on November 26, 2011, the Curiosity rover, a nuclear-powered robotic vehicle, bearing instruments designed to assess past and present habitability conditions on Mars. The Curiosity rover landed on Mars on Aeolis Palus in Gale Crater, near Aeolis Mons (a.k.a. Mount Sharp), on August 6, 2012.
On 16 December 2014, NASA reported the Curiosity rover detected a "tenfold spike", likely localized, in the amount of methane in the Martian atmosphere. Sample measurements taken "a dozen times over 20 months" showed increases in late 2013 and early 2014, averaging "7 parts of methane per billion in the atmosphere." Before and after that, readings averaged around one-tenth that level.
In addition, low levels of chlorobenzene (C
5Cl), were detected in powder drilled from one of the rocks, named "Cumberland", analyzed by the Curiosity rover.
Future astrobiology missions[edit | hide | edit source]
- ExoMars is a European-led multi-spacecraft programme currently under development by the European Space Agency (ESA) and the Russian Federal Space Agency for launch in 2016 and 2020. Its primary scientific mission will be to search for possible biosignatures on Mars, past or present. A rover with a 2 m (6.6 ft) core drill will be used to sample various depths beneath the surface where liquid water may be found and where microorganisms (or organic biosignatures) might survive cosmic radiation.

Is hydrogen the secret to water on Mars?
An unlikely greenhouse gas could have absorbed enough heat to keep liquid water stable on the surface of Mars about 4 billion years ago, argue scientists in a new article.
Mars has valleys deeper than the Grand Canyon, braided river channels, and a level seashore reaching around the northern third of the planet. These signs point to water – a lot of water – in Mars's early history. But it's too cold for liquid water now, so how could Mars have had rivers and oceans 3.8 billion years ago, back when the sun was colder and dimmer?
Just add hydrogen, suggests a team of scientists from Penn State and NASA. "A CO2 -H2 greenhouse could have done the trick," writes Ramses Ramirez, lead author of a new paper appearing in the Nov. 24 Nature Geoscience.
"You just need a little nudge," explains Jim Kasting, a Penn State professor and fellow author on the paper. "On early Mars, you can almost make it warm enough with carbon dioxide and water vapor, but not quite. You need something to push you over the edge."
Ever since the valleys were discovered in the 1970s, scientists have been trying to explain how a cold planet with a negligible atmosphere could ever have been warm enough to have running water on the surface. It hasn't been easy. Various greenhouse gases have been suggested – carbon dioxide, sulfur dioxide, water vapor – but none were abundant enough to keep Mars balmy. Also, many gases create clouds, which undercut their greenhouse effectiveness by reflecting sunlight back up into space.
Considering all the problems with keeping Mars warm, some scientists have considered a series of "transient" atmospheres. They argue that big meteor impacts could blast enough material into Mars's sky to create a temporary atmosphere that would heat the planet into a brief warm spell, lasting just long enough to flash-thaw huge chunks of ice into catastrophic floods that would pour across the surface, quickly carving the visible channels and valleys.
But the longer we look at Mars, the more valleys and channels we find, note Ramirez and Kasting. Big ones. The amount of water required to carve and shape them just isn't compatible with flash-in-the-pan transient atmospheres, they argue. So they set out to model a stable, warm climate on early Mars.
Hydrogen: an unlikely hero
They got a hint from the hydrogen-rich atmosphere of the outer planets.

For example, Olympus Mons is a massive (extinct) Martian volcano and is actually the largest volcano known to exist—nearly three times as tall as Mt. Everest. Yet, even though its base would cover the combined states of Ohio, Indiana, and Kentucky, a mild gradient makes Olympus Mons seem far less impressive than the rugged slopes of Everest. Several other immense volcanoes exist on Mars, dwarfing their terrestrial counterparts. Most astronomers believe that all of these volcanoes are extinct and that Mars currently has essentially no geologic activity.
One of Mars’ most spectacular features is a canyon called Valles Marineris that is long enough to reach from one end of the United States to the other and is over 120 miles wide and about four miles deep.3 For comparison, this is ten times longer, nearly seven times wider, and four times deeper than the Grand Canyon. Valles Marineris is thought to be a tectonic fissure—a place where the surface cracked open.4
Scientists have been intrigued to learn that the surface of Mars has dry river beds and deltas. Though there is essentially no liquid water on the planet today, evidence clearly suggests that Mars once had surface water. Such evidence is especially perplexing in light of the planet’s thin atmosphere. Water can only exist as a liquid between certain temperatures and under sufficient atmospheric pressures, and the atmosphere of Mars is far too thin to allow water to be liquid for any length of time at any temperature. Heating an ice cube on Mars would cause it to sublime, not melt. That is, the ice would go directly to vapor, bypassing the liquid state entirely. Frozen carbon dioxide behaves in the same way under Earth’s atmosphere.
So, was the atmosphere of Mars different in the past? Or was the water released catastrophically, boiling away almost immediately? Could volcanic eruptions increase the atmospheric pressure locally to the point where liquid water could exist temporarily? These are mysteries that remain unsolved. It is noteworthy that secularists are willing to believe in catastrophic, planet-scale flooding on Mars—a planet that cannot support liquid water. Yet, they simultaneously deny the Genesis Flood on Earth—a planet that is 71 percent covered with water.
The two moons of Mars are quite tiny compared to Earth’s moon. Phobos is the larger of the two and only about 10 miles in diameter. Since Phobos has so little mass, its gravity is minuscule.

Sulfur in the early Martian atmosphere revisited: Experiments with a 3-D global climate model. Icarus, 261, 133–148.
- Kieffer, H. H., & Zent, A. P. (1992). Quasi-periodic climate change on Mars. In H. H. Kieffer, B. M. Jakosky, C. W. Snyder, & M. S. Matthews (Eds.), Mars (pp. 1180–1218). University of Arizona Press.
- Kite, E. S., Gao, P., Goldblatt, C., Mischna, M. A., Mayer, D. P., & Yung, Y. L. (2017). Methane bursts as a trigger for intermittent lake-forming climates on post-Noachian Mars. Nature Geoscience, 10, 737–740.
- Kite, E. S., Steele, L. J., Mischna, M. A., & Richardson, M. I. (2021). Warm early Mars surface enabled by high-altitude water ice clouds. Proceedings of the National Academy of Sciences of the USA, 118(18), e2101959118.
- Kite, E. S., Williams, J.-P., Lucas, A., & Aharonson, O. (2014). Low palaeopressure of the Martian atmosphere estimated from the size distribution of ancient craters. Nature Geoscience, 5, 335–339.
- Koutnik, M., Byrne, S., & Murray, B. (2002). South polar layered deposits of Mars: The cratering record. Journal of Geophysical Research, 107(E11), 10-1–10-10.
- Kreslavsky, M. A., & Head, J. W. (2000). Kilometer-scale roughness of Mars’ surface: Results from MOLA data analysis. Journal of Geophysical Research, 105, 26695–26712.
- Kreslavsky, M. A., & Head, J. W. (2002).

Secondly, there are no processes underway that could lead to a collapse in the Martian atmosphere.
Nevertheless, if an incident of this kind were to eject water molecules into space, once they have acquired 'escape velocity', they would no longer be influenced by the gravitational pull of Mars. Therefore, theoretically, these molecules could drift further into the Solar System and at some stage might be captured by Earth's gravitational field. The majority of this 'Martian water' would originate from the surface of Mars (ice deposits at the north and south poles), or from layers of ice beneath the planet's surface. Today’s Martian atmosphere contains just 210 parts per million water molecules, which is negligible. So initially, it would be molecules, atoms or ions of carbon dioxide (96 percent), nitrogen (1.9 percent, argon (1.9 percent), oxygen (0.15 percent) and carbon monoxide (0.06 percent) – in descending order of their relative contribution to the Martian atmosphere – that would arrive before water molecules.
If this transfer of water molecules from Mars to Earth did indeed occur, it would be possible, in theory at least, to identify them as 'Martian', based on their slightly different isotope composition (the relative proportions of different 'types' of hydrogen and oxygen atoms in the water molecules). However, given that it is likely to be very, very, very few atoms, any kind of identification using current analysis techniques is probably impossible.
The situation with tiny gaseous inclusions found in meteorites is slightly different. Some meteorites have been found that must have originated from Mars, as they contain small pockets of gas in which the noble gas argon is found in similar concentrations to those that orbiters have measured in the Martian atmosphere. This is considered definite proof of their origin.

Tim Parker of NASA's Jet Propulsion Laboratory first proposed such an idea in 1989. Parker, examining images taken by the Viking Orbiters, found what he believed were remnants of two ancient ocean shorelines, which he called "contacts," one inside the other, in the Martian north.
Expanding on this notion, in 1991 Vic Baker of the University of Arizona, suggested that Mars might not be geologically dead and permanently frozen. Instead, he proposed, Mars might undergo cycles, or pulses -- first heating up, releasing groundwater and forming an ocean in the north, then dissipating the ocean back into the planet's crust and re-freezing.
More recently, Jim Head and colleagues at Brown University, found evidence that is consistent with a shoreline that might indeed have existed at the inner of Parker's two proposed contacts, contact 2. Head and colleagues examined elevation data gathered by the Mars Orbiter Laser Altimeter (MOLA) on board the Mars Global Surveyor (MGS) and found that the elevation at points along contact 2 were much closer to a straight line than those at contact 1. They also found that the terrain below this elevation was smoother than the terrain above it. Both of these findings are consistent with the former presence there of an ocean.
But the story doesn't end there. Shortly after Head and colleagues published their findings, Mike Malin and Ken Edgett of Malin Space Systems used the Mars Orbital Camera (MOC) aboard MGS, to take a series of high-resolution images of contact 2 terrain. Their conclusion: there's nothing there.
Right: In this topographic drawing of Mars, blue indicates the area where an ocean once may have existed. Credit: NASA Mars Global Surveyor Project; MOLA Team Rendering by Peter Neivert, Brown University
And the debate continues. Says Mike Carr of the U.S. Geological Survey, author of the book Water on Mars, "We're getting all this new data from MGS, and I think a lot of it is just not understood yet. It's very hard to understand. The whole business of the oceans, the evidence is so contradictory."
Mars's small-valley networks, which occur mainly in the southern highlands, pose another perplexing problem. Scientists who first studied images of these valleys thought they resembled river valleys on Earth.

In his explanation of the most intriguing of the biology tests, the Viking labeled release (LR) experiment, Oyama built upon an idea first suggested by John Oro, of the molecular analysis team (responsible for the Viking gas chromatograph-mass spectrometer). Oro had suggested early on that the results from both the GEX and LR experiments were due to the presence of peroxidelike materials in the Martian soil. In Oyama's view, hydrogen peroxide formed photochemically in the atmosphere and reacted with a catalyst on the surface of the soil grains to form oxygen which then diffused into the grains, reacting with the alkaline earths and metals to form superoxides. Atmospheric water vapor converts the superoxides to peroxides, which combined with water in the LR nutrient to form hydrogen peroxide. This in turn oxidized the labeled components of the nutrients to release the observed labeled carbon dioxide. As for the observed release of oxygen, Oyama pointed to what happens when hydrogen peroxide, a commonly used disinfectant, is applied to a wound. Bubbles of oxygen form as a result of the catalytic action of iron (present in blood hemoglobin) on hydrogen peroxide. A similar process operates on Mars, but in this case, suggested Oyama, the catalyst is probably a form of iron oxide known as maghemite.
Related categories MARS TOPICS
Home • About • Copyright © The Worlds of David Darling • Encyclopedia of Alternative Energy • Contact

That discovery may help us work out when and how the Red Planet lost most of its atmosphere (see "Heavy hydrogen bombshell").
Curiosity is now getting ready for its trek to Aeolis Mons, taking in other points of interest en route. Grotzinger likens Curiosity to a car with a 10,000-page user manual that was still being written as the science team tested its instruments. With all the gear up and running, it's time to drive, he says. "Our car is ready to go."
Heavy hydrogen bombshell
Gravity means everything is lighter on Mars, but it seems the Red Planet likes its hydrogen heavy. In its first chemical analysis of the Martian soil, the Curiosity rover has found an unusually high proportion of deuterium, also known as heavy hydrogen. The finding may help pin down when and how Mars lost most of its atmosphere.
Most hydrogen atoms consist of a proton and an electron, but some also boast a neutron, forming deuterium. On Earth, deuterium is much rarer than hydrogen. For example, in our oceans, there is one deuterium atom to every 6420 hydrogen atoms. As deuterium is thought to have been produced in the big bang, it should once have had similar abundances on all the planets in the solar system. But when Curiosity's Sample Analysis at Mars experiment (SAM) vaporised Martian soil, it found a ratio five times higher: one deuterium for every 1284 hydrogens.
That could help pin down when Mars's atmosphere, today much thinner than Earth's, started, for some reason, to dissipate. Paul Mahaffy, SAM's principal investigator, suggests that Mars could have lost its light hydrogen when its climate was warmer and wetter. Ultraviolet light from the sun could have broken up water in the atmosphere, creating free hydrogen. The lighter isotope would then have escaped into space more rapidly, leaving proportionately more deuterium behind. That version of events would be strengthened if the rover finds hydrated minerals - signs of water from a bygone era - on the slopes of Aeolis Mons, a mountain that may preserve a layered geological history.
A model of the early environment will help determine whether Mars was conducive to life, Mahaffy says.
- New Scientist
- Not just a website!

- 2 updates
The evidence "seems to be building that we are actually all Martians" and "that life started on Mars and came to Earth on a rock," according to a scientist from The Westheimer Institute for Science and Technology in the US.
Professor Steven Benner said, "It's lucky that we ended up here nevertheless, as certainly Earth has been the better of the two planets for sustaining life. If our hypothetical Martian ancestors had remained on Mars, there might not have been a story to tell."
Prof Benner told the Goldschmidt 2013 conference in Italy that the oxidised mineral form of the element molybdenum, "couldn't have been available on Earth at the time life first began, because three billion years ago the surface of the Earth had very little oxygen, but Mars did".
"It's yet another piece of evidence which makes it more likely life came to Earth on a Martian meteorite, rather than starting on this planet," he added.
Life on Earth may have started on Mars, a major science conference has heard.
An element believed to be crucial to the origin of life would only have been available on the surface of the Red Planet, Geochemist Professor Steven Benner claims.
Professor Benner argues that the "seeds" of life probably arrived on Earth in meteorites blasted off Mars by impacts or volcanic eruptions.
He points to the oxidised mineral form of the element molybdenum, thought to be a catalyst that helped organic molecules develop into the first living structures, as evidence of his theory.

Xenon fractionation data support this possibility. Thus, an early impact-generated atmosphere that accumulated during accretion was likely rapidly lost to space (Scherf & Lammer, 2021).
A secondary atmosphere then developed from outgassing of the planet’s interior. As the planet cooled, convection within the core generated a dynamo and magnetic field that would have offered some protection to the growing atmosphere from solar wind stripping, but not EUV. The composition of this secondary atmosphere would have depended on the mantle redox state. As is the case for Mars, rapid core formation would quickly separate iron from volatiles favoring a more oxidized mantle like that of Earth where outgassed volatiles would have been dominated by H2O, CO2, and SO2. However, some of the SNC meteorites2 indicate a more reduced mantle than that of Earth, in which case H2, CO, CH4, and H2S would have been favored. Complicating matters further is the fact that the early outgassing history is not known and EUV-driven thermal escape (Tian et al., 2009) could have significantly depleted any pre-Noachian atmosphere. Thus, the mass, composition, and fate of a secondary pre-Noachian atmosphere between 4.1 and 4.5 Gy are highly uncertain, and this atmosphere may even have been largely absent (see Scherf & Lammer, 2021).
By the beginning of the Noachian (4.1 Gy), however, rapid thermal escape would no longer be operative because of the decline in the EUV flux. However, impact erosion during a possible Late Heavy Bombardment period3 could be a factor (Melosh & Vickery, 1989). And the loss of the magnetic field would have exposed the atmosphere to the solar wind. Nevertheless, the buildup of a thick atmosphere would have been possible if outgassing rates exceeded loss rates. Because the Tharsis volcanic province is believed to have been constructed during the Noachian, enhanced outgassing rates were likely at this time. Phillips et al. (2001) estimate that Tharsis could have outgassed 1.5 bars of CO2. Thus, it is plausible that a thick atmosphere developed during the Noachian.

The sustainability of habitability on terrestrial planets: Insights, questions, and needed measurements from Mars for understanding the evolution of Earth-like worlds. Journal of Geophysical Research: Planets, 1231, 1927–1961.
- Elkins-Tanton, L. T., Hess, P. C., & Parmentier, E. M. (2005). Possible formation of ancient crust on Mars through magma ocean processes. Journal of Geophysical Research, 110(E12).
- Fanale, F. P., & Cannon, W. A. (1978). Mars: The role of the regolith in determining atmospheric pressure and the atmosphere’s response to insulation changes. Journal of Geophysical Research, 83, 2321–2325.
- Fassett, C. I., & Head, J. W. (2008). The timing of Martian valley network activity: Constraints from buffered crater counting. Icarus, 195, 61–89.
- Feldman, W. C., Boynton, W. V., Tokar, R. L., Prettyman, T. H., Gasnault, O., Squyres, S. W., Elphic, R. C., Lawrence, D. J., Lawson, S. L., Maurice, S., McKinney, G. W., Moore, K. R., & Reedy, R. C. (2002). Global distribution of neutrons from Mars: Results from Mars Odyssey. Science, 297, 75–78.
- Forget, F., Byrne, S., Head, J. W., Mischna, M. A., & Schörghofer, N. (2017). Recent climate variations. In R. M. Haberle, R. T. Clancy, F. Forget, M. D. Smith, & R. W. Zurek (Eds.), The atmosphere and climate of Mars (pp. 497–525). Cambridge University Press.
- Forget, F., Haberle, R. M., Montmessin, F., Levrard, B., & Head, J. W. (2006). Formation of glaciers on Mars by atmospheric precipitation at high obliquity. Science, 311, 368–371.

“Nitrogen isotopes tell a story about oxygenation of the surface ocean, and this oxygenation spans hundreds of kilometers across a marine basin and lasts for somewhere less than 50 million years.”
The team analyzed drill samples taken by Buick in 2012 at another site in the northwestern part of Western Australia called the Jeerinah Formation.
The researchers drilled two cores about 300 kilometers apart but through the same sedimentary rocks — one core samples sediments deposited in shallower waters, and the other samples sediments from deeper waters. Analyzing successive layers in the rocks years shows, Buick said, a “stepwise” change in nitrogen isotopes “and then back again to zero. This can only be interpreted as meaning that there is oxygen in the environment. It’s really cool — and it’s sudden.”
The nitrogen isotopes reveal the activity of certain marine microorganisms that use oxygen to form nitrate, and other microorganisms that use this nitrate for energy. The data collected from nitrogen isotopes sample the surface of the ocean, while selenium suggests oxygen in the air of ancient Earth. Koehler said the deep ocean was likely anoxic, or without oxygen, at the time.
The team found plentiful selenium in the shallow hole only, meaning that it came from the nearby land, not making it to deeper water. Selenium is held in sulfur minerals on land; higher atmospheric oxygen would cause more selenium to be leached from the land through oxidative weathering — “the rusting of rocks,” Buick said — and transported to sea.
“That selenium then accumulates in ocean sediments,” Koehler said. “So when we measure a spike in selenium abundances in ocean sediments, it could mean there was a temporary increase in atmospheric oxygen.”
The finding, Buick and Koehler said, also has relevance for detecting life on exoplanets, or those beyond the solar system.
“One of the strongest atmospheric biosignatures is thought to be oxygen, but this study confirms that during a planet’s transition to becoming permanently oxygenated, its surface environments may be oxic for intervals of only a few million years and then slip back into anoxia,” Buick said.
“So, if you fail to detect oxygen in a planet’s atmosphere, that doesn’t mean that the planet is uninhabited or even that it lacks photosynthetic life. Merely that it hasn’t built up enough sources of oxygen to overwhelm the ‘sinks’ for any longer than a short interval.

The study determined that perchlorate —discovered in 2008 by Phoenix lander— can destroy organic compounds when heated, and produce chloromethane and dichloromethane as byproduct, the identical chlorine compounds discovered by both Viking landers when they performed the same tests on Mars. Because perchlorate would have broken down any Martian organics, the question of whether or not Viking found organic compounds is still wide open.
The Labeled Release evidence was not generally accepted initially, and, to this day lacks the consensus of the scientific community.
Meteorites[edit | hide | edit source]
NASA maintains a catalog of 34 Mars meteorites. These assets are highly valuable since they are the only physical samples available of Mars. Studies conducted by NASA's Johnson Space Center show that at least three of the meteorites contain potential evidence of past life on Mars, in the form of microscopic structures resembling fossilized bacteria (so-called biomorphs). Although the scientific evidence collected is reliable, its interpretation varies. To date, none of the original lines of scientific evidence for the hypothesis that the biomorphs are of exobiological origin (the so-called biogenic hypothesis) have been either discredited or positively ascribed to non-biological explanations.
Over the past few decades, seven criteria have been established for the recognition of past life within terrestrial geologic samples. Those criteria are:
- Is the geologic context of the sample compatible with past life?
- Is the age of the sample and its stratigraphic location compatible with possible life?
- Does the sample contain evidence of cellular morphology and colonies?
- Is there any evidence of biominerals showing chemical or mineral disequilibria?
- Is there any evidence of stable isotope patterns unique to biology?
- Are there any organic biomarkers present?
- Are the features indigenous to the sample?
For general acceptance of past life in a geologic sample, essentially most or all of these criteria must be met. All seven criteria have not yet been met for any of the Martian samples, but continued investigations are in progress.
As of 2010, reexaminations of the biomorphs found in the three Martian meteorites are underway with more advanced analytical instruments than previously available.

Curiosity draws a blank on Martian methane
No gas, no life? After more than a month of searching, scientists using NASA's rover Curiosity to study Mars' atmosphere have found no evidence that the planet has methane, a gas tied to biological processes.
The finding adds a new twist into a puzzling story about methane on Mars, which previously was detected by ground-based telescopes and orbiting spacecraft.
"Maybe it's understandable because it's a very early measurement and they're just really still learning the idiosyncrasies of the instrumentation," says planetary scientist Michael Mumma, with NASA's Goddard Space Flight Center.
Mumma led a team that found methane in Mars' atmosphere in 2003.
On Earth, living systems produce more than 90 per cent of the methane in the atmosphere, with the rest tied to geochemical processes. The gas is easily broken down by sunlight, so its presence in the Martian atmosphere would imply a continuous source on the planet's surface.
But on Mars, solar radiation is likely not the only methane-killer, nor the most lethal.
For example, the planet's atmosphere and soil is believed to contain chemicals that are highly destructive to molecular bonds, including those in methane.
"The oxidation process could start in the atmosphere and diffuse into the surface of Mars. There possibly are oxidants in the surface of Mars, including hydrogen peroxide ... that could potentially result in the rapid destruction of methane," says Curiosity scientist Sushil Atreya with the University of Michigan in Ann Arbor.
Mars' dust storms could play a role as well, blasting methane-busting chemicals into the atmosphere, as well as generating massive electrical fields that could directly destroy the gas, Atreya adds.
Curiosity landed on Mars in August to determine if the planet has or ever had the ingredients needed to develop and preserve life. The rover includes a suite of science instruments to chemically analyse soil, rock and atmospheric samples.
Rover scientists found methane in the first two atmospheric samples analysed by the rover's Sample Analysis at Mars (SAM) instrument, but believe the gas was a remnant from Earth. Two more experiment runs did not find methane in concentrations of at least five parts per billion.
Mumma says that's not surprising.
"A year-and-a-half after we published our results, we noted that the global mean average had decreased to about three parts per billion.

- Staff (28 September 2015). "Video Highlight - NASA News Conference - Evidence of Liquid Water on Today's Mars". NASA. Archived from the original on October 1, 2015. Retrieved 30 September 2015.
- Staff (28 September 2015). "Video Complete - NASA News Conference - Water Flowing on Present-Day Mars m". NASA. Archived from the original on October 15, 2015. Retrieved 30 September 2015.
- Ojha, L.; Wilhelm, M. B.; Murchie, S. L.; McEwen, A. S.; Wray, J. J.; Hanley, J.; Massé, M.; Chojnacki, M. (2015). "Spectral evidence for hydrated salts in recurring slope lineae on Mars". Nature Geoscience. 8 (11): 829–832. Bibcode:2015NatGe...8..829O. doi:10.1038/ngeo2546.
- "Mars Reconnaissance Orbiter Telecommunications" (PDF). JPL. September 2006. Archived (PDF) from the original on February 15, 2013.
- Luhmann, J. G.; Russell, C. T. (1997). "Mars: Magnetic Field and Magnetosphere". In Shirley, J. H.; Fainbridge, R. W. Encyclopedia of Planetary Sciences. New York: Chapman and Hall. pp. 454–6.
- Phillips, Tony (January 31, 2001). "The Solar Wind at Mars". NASA. Archived from the original on August 18, 2011.
- "What makes Mars so hostile to life?". BBC News. January 7, 2013. Archived from the original on August 30, 2013.
- Keating, A.; Goncalves, P. (November 2012). "The impact of Mars geological evolution in high energy ionizing radiation environment through time". Planetary and Space Science – Eslevier. 72 (1): 70–77. Bibcode:2012P&SS...72...70K. doi:10.1016/j.pss.2012.04.009.

- Levin, Gilbert V.; Straat, Patricia Ann (2009). "Methane and life on Mars". In Hoover, Richard B; Levin, Gilbert V; Rozanov, Alexei Y; Retherford, Kurt D. Instruments and Methods for Astrobiology and Planetary Missions XII. 7441. pp. 12–27. Bibcode:2009SPIE.7441E..12L. doi:10.1117/12.829183. ISBN 978-0-8194-7731-6.
- Oze, Christopher; Jones, Camille; Goldsmith, Jonas I.; Rosenbauer, Robert J. (June 7, 2012). "Differentiating biotic from abiotic methane genesis in hydrothermally active planetary surfaces". PNAS. 109 (25): 9750–9754. Bibcode:2012PNAS..109.9750O. doi:10.1073/pnas.1205223109. PMC . PMID 22679287.
- Staff (June 25, 2012). "Mars Life Could Leave Traces in Red Planet's Air: Study". Space.com. Archived from the original on June 30, 2012.
- Brogi, Matteo; Snellen, Ignas A. G.; de Krok, Remco J.; Albrecht, Simon; Birkby, Jayne; de Mooij, Ernest J. W. (June 28, 2012). "The signature of orbital motion from the dayside of the planet τ Boötis b". Nature. 486 (7404): 502–504. arXiv: . Bibcode:2012Natur.486..502B. doi:10.1038/nature11161. PMID 22739313.
- Mann, Adam (June 27, 2012). "New View of Exoplanets Will Aid Search for E.T." Wired. Archived from the original on August 29, 2012.
- Webster, Guy; Neal-Jones, Nancy; Brown, Dwayne (December 16, 2014). "NASA Rover Finds Active and Ancient Organic Chemistry on Mars". NASA. Archived from the original on December 17, 2014.