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Published: Sat, June 09, 2018
Research | By Jennifer Evans

NASA finds more evidence that Mars could have once supported life

NASA finds more evidence that Mars could have once supported life

NASA's Curiosity rover 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. There is no way for Curiosity to determine if the materials it found came from ancient Martian life or not, according to Eigenbrode.

While all of these findings could point to life on the planet, there could be other explanations.

"Are there signs of life on Mars?" asked Michael Meyer, lead scientist for the Mars Exploration Program at NASA Headquarters.

'Curiosity has not determined the source of the organic molecules, ' said Jen Eigenbrode of NASA's Goddard Space Flight Center in Greenbelt, Maryland, who is lead author of one of the two new Science papers. While commonly associated with life, organic molecules can also be created by non-biological processes and are not necessarily indicators of life. The space agency announced Thursday that its Curiosity rover had uncovered "tough" organic molecules preserved in three-billion-year-old rocks in the planet's Gale Crater, which is believed to have once contained a shallow lake.

Curiosity sampled sites by drilling five centimeters below the surface in the Gale crater, which is where the rover landed in 2012.

Siebach said that while neither of the new discoveries "require life in the past or present, they present compelling evidence that Martian life could have existed in the past, that if it did we have a chance of finding evidence of it, and that there are ongoing reactions deep below the surface of Mars that could potentially be related to liquid water or life". The mudstone gradually formed from silt that settled out of the water and accumulated at the bottom of the lake.

And although hopes were high that the two landers and their instruments would detect signs of life or organic compounds in samples taken from the surface, that didn't happen. While water-rock chemistry might have produced those variations, NASA said it "cannot rule out the possibility of biological origins". The organic molecules and volatiles, comparable to samples of sedimentary rock rich in organics on Earth, included thiopene, methylthiophenes methanethiol and dimethylsulfide.

"Methane previously had been detected in Mars' atmosphere in large, unpredictable plumes".

The organic molecules identified by Curiosity and NASA scientists were found in samples of mudstone collected from the ancient lakebed inside Gale Crater. Some of these fragments contain sulfur, which could have helped preserve them in the same way sulfur is used to make vehicle tires more durable, according to Eigenbrode. This new result shows that low levels of methane within Gale Crater repeatedly peak in warm, summer months and drop in the winter every year.

The results indicate organic carbon concentrations on the order of 10 parts per million or more.

'Both these findings are breakthroughs in astrobiology, ' says Inge Loes ten Kate, at Utrecht University, the Netherlands, who wrote a perspective piece about the studies in Science.

Like meteorites crashing into Mars. That leaves open the possibility that microorganisms once populated our planetary neighbor and might still exist there.

"This is the first time we've seen something repeatable in the methane story, so it offers us a handle in understanding it", said Dr. Chris Webster, a scientist at NASA's Jet Propulsion Laboratory.

Almost all of Earth's methane is biologically produced, so when methane was first detected in Mars' atmosphere in 2003 it immediately generated excitement - although its origins remain unknown. The methane then seeps to the surface through cracks and fissures, and processes linked to surface temperature control the release of the gas to produce the seasonal cycle.

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