Jennifer Eigenbrode, an astrobiologist at NASA's Goddard Space Flight Center in Greenbelt, Maryland who led the organics study, said she's intrigued by the possibility that life might have existed and adapted on Mars.
Curiosity also has confirmed sharp seasonal increases of methane in the Martian atmosphere.
The search for life on Mars over the past half century has been an exercise in lowering the bar combined with ever more sophisticated ways of seeking clues.
"Are there signs of life on Mars?" said Michael Meyer, lead scientist for NASA's Mars Exploration Program, at NASA Headquarters.
Since Curiosity landed on Mars in 2012, the rover has been exploring Gale Crater, a massive impact crater roughly the size of CT and Rhode Island, for geological and chemical evidence of the chemical elements and other conditions necessary to sustain life. The significance of the finding, however, is that the results show organic matter can be preserved in Mars surface sediments. A smaller discovery was announced in 2014.
'Before this discovery we did not know if organic compounds existed in rocks on Mars, ' says Sanjeev Gupta, a planetary scientist at Imperial College London who collaborated in the study. Even more compelling was the fact that these compounds seemed to have broken off even bigger, more complex "macromolecules" - substances found on Earth in coal, black shale and other ancient organic remains.
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MIT News checked in with SAM team member Roger Summons, the Schlumberger Professor of Geobiology at MIT, and a co-author on the Science paper, about what the team's findings might mean for the possibility of life on Mars. Most of Earth's atmospheric methane comes from animal and plant life, and the environment itself.
Their precise source is still a mystery. "We were just blown away", he said. They thought mudstone rocks, formed from silt accumulated at the bottom of the ancient lake, might hold some clues and analyzed the powdered samples from Curiosity's Sample Analysis at Mars instrument suite. "We also don't know if that methane was created from rock chemistry or it was created by microbes".
The other paper in Science reported on new details in the search for the source of methane on Mars, which has wide spikes and dips according to the seasons.
The lab, nicknamed SAM, identified several fragments of larger organic molecules that don't easily vaporize. Schiaparelli ended up crashing into the Martian surface, but TGO arrived safely and recently settled into its final orbit. In an accompanying article, Inge Loes ten Kate of the Department of Earth Sciences in the Netherlands' Utrecht University described them as "breakthroughs in astrobiology". The release of methane is an active process on Mars, which could suggest new things about what's unfolding on the Red Planet.
Finding methane in the atmosphere and ancient carbon preserved on the surface gives scientists confidence that NASA's Mars 2020 rover and ESA's (European Space Agency's) ExoMars rover will find even more organics, both on the surface and in the shallow subsurface.
Using their fleet of Martian rovers and satellites, scientists have been searching for geochemical signs of ancient life. So what if scientists were able to drill 10 meters, 100 meters, 1,000 meters?
NASA also has another rover in the works with its Mars 2020 mission, which plans to drill cores and set them aside for a possible future pickup and return to Earth.