Signs of water, and signs of life– recent news from Mars is showing increased signs of both!

For the former: new long-term analysis has found that water may have been present on the Martian surface for longer than originally anticipated.  Additionally, the discovery of abundant carbon isotopes associated with biological functions adds to a growing mountain of evidence that life may exist on the Red Planet.

Using the 16 years worth of data collected by the Mars Reconnaissance Orbiter (MRO), researchers at NASA’s Jet Propulsion Laboratory (JPL) have found that water appears to have been present on the Martian surface much later than originally estimated, lasting until at least 2 billion years ago, stretching the timeframe of a wet Mars by roughly a billion years.

The research team used the MRO data to conduct a survey of salt deposits present in meteorite craters on the Martian surface, including craters that were as small as the space probe itself; these results were then compiled against the age of the regions surveyed, a factor determined by the relative scarring of the surface by meteorite impacts: younger surface conditions would sport fewer impact craters, and older regions would show a more meteor-wary face.

If this timeline is correct, it allows Mars a great deal more time for the chance to develop complex life forms: although life appeared on Earth only a few hundred million years after the planet’s formation, it wasn’t until between 2.4 and 2 billion years ago that carbon dioxide-breathing cyanobacteria were able to produce enough oxygen to allow more efficient O2-breathing creatures to develop, an important step in allowing the proliferation of multi-cellular creatures to evolve 1.5 billion years later during the Cambrian explosion. If Mars was following the same timeline and the taps were shut off 3 billion years ago as was previously assumed, that early lack of water might have put a damper on more complex Martian life before it had a chance to evolve.
To that end, a new development on the Martian surface, courtesy of NASA’s Curiosity Rover, has uncovered the presence of substantial amounts of a carbon isotope—specifically, carbon-12—that is associated with biological processes.

Having explored Mars’ Gale Crater for nearly a decade, the robust rover has discovered soil deposits containing carbon isotopes, including the element’s two most common flavors: carbon-12 and carbon-13. Although both isotopes are stable (unlike their unstable counterpart, carbon-14), carbon-12’s weaker chemical bonds produce more active chemical reactions, meaning it winds up being favored over carbon-13 in biological processes, and thus winds up being the dominant carbon isotope in the biological compounds that result from said processes.

“The amounts of carbon-12 and carbon-13 in our Solar System are the amounts that existed at its formation. Both exist in everything, but because carbon-12 reacts more quickly than carbon-13, looking at the relative amounts of each in samples can reveal the carbon cycle,” explains Penn State Department of Geosciences researcher Professor Christopher House.

Although the ratios between C-12 and C-13 varied wildly between samples from different areas of Gale Crater, the C-13-poor samples “are a little like samples from Australia taken from sediment that was 2.7 billion years old,” House said. However, he cautions that “those [Australian] samples were caused by biological activity when methane was consumed by ancient microbial mats, but we can’t necessarily say that on Mars because it’s a planet that may have formed out of different materials and processes than Earth.”

Although the proliferation of carbon-12 on Earth is typically due to Earthlings going about their biological business, House and his team can’t definitively point a finger to a biological source for the imbalanced C-12 and C-13 isotopes without more direct evidence of microbes in the Martian soil.

They offer a number of non-biological sources as possible explanations for this isotopic imbalance, including the Solar System having passed through a cosmic dust cloud at some point, or the breaking down of carbon dioxide or methane by ultraviolet radiation. Regardless, “all three possibilities point to an unusual carbon cycle unlike anything on Earth today,” according to Professor House.

He went on to point out that “we need more data to figure out which of these is the correct explanation. It would be nice if the rover would detect a large methane plume and measure the carbon isotopes from that, but while there are methane plumes, most are small, and no rover has sampled one large enough for the isotopes to be measured.”

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