NASA's Curiosity rover has found further evidence of organic matter within rocks on the surface of Mars, lending more weight to the belief that the ‘red planet' may once have supported life.
The new findings, NASA claimed in a press conference yesterday, include evidence of what it described as "tough" organic molecules in three-billion-year-old sedimentary rocks near the surface, as well as seasonal variations in the levels of methane in the atmosphere.
NASA's findings have been published today in two papers in the journal Science.
While another indication that Mars might once have supported life, it is not conclusive proof, the US space agency was keen to assert. The molecules were preserved within Gale Crater on Mars.
Organic molecules contain carbon and hydrogen, and also may include oxygen, nitrogen and other elements. While commonly associated with life, organic molecules can also be created by non-biological processes and are not necessarily indicators of life.
"With these new findings, Mars is telling us to stay the course and keep searching for evidence of life," said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA. "I'm confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the red planet."
"Curiosity has not determined the source of the organic molecules," added Jen Eigenbrode of NASA's Goddard Space Flight Center, lead author of one of the two new Science papers. "Whether it holds a record of ancient life, was food for life, or has existed in the absence of life, organic matter in Martian materials holds chemical clues to planetary conditions and processes."
The findings of organic matter come on top of evidence that the surface of Mars once had liquid water, indicating that its atmosphere once enabled temperatures that could have supported life.
In 2012, NASA released evidence from the Curiosity rover that suggested that Gale Crater on Mars "held all the ingredients necessary for life, including chemical building blocks and energy sources".
"The Martian surface is exposed to radiation from space. Both radiation and harsh chemicals break down organic matter," said Eigenbrode. "Finding ancient organic molecules in the top five centimetres of rock that was deposited when Mars may have been habitable, bodes well for us to learn the story of organic molecules on Mars with future missions that will drill deeper."
To identify organic material in the Mars' soil, the Curiosity rover drilled into sedimentary rocks, known as mudstone, from four areas in Gale Crater.
This mudstone was formed gradually billions of years ago from silt that accumulated at the bottom of the ancient lake. The rock samples were analysed by a device that uses an oven to heat the samples to 500 degrees Celsius to release organic molecules from the powdered rock.
The results suggest organic carbon concentrations of around 10 parts per million - about the same as the level observed in Martian meteorites and 100 times greater than earlier detections of organic carbon on Mars, explained NASA.
In the second of the two papers published in Science, NASA scientists describe seasonal variations of methane in Mars' atmosphere observed over three Mars years - or six Earth years. The presence of methane is significant because it may have organic origins, like methane gas on Earth.
The new analysis shows that low levels of methane within Gale Crater repeatedly peak in warm, summer months and drop in the winter every year.
Finding evidence of life on Mars will indicate that other planets across the universe with the right ‘ingredients' almost certainly do contain life - whether those life forms are capable of inventing and wearing digital watches is another matter, however.
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