"Data from Curiosity reveal that billions of years ago, a water lake inside Gale Crater held all the ingredients necessary for life, including chemical building blocks and energy sources".
That leaves open the possibility that microorganisms once populated the red planet - and still might.
"While we don't know the source of the material, the awesome consistency of the results makes me think we have a slam-dunk signal for organics on Mars", said Jennifer Eigenbrode, a biogeochemist at Nasa's Goddard Space Flight Centre. Using SAM, Webster and his colleagues have found a persistent background level of methane in the atmosphere above Gale Crater over the last five years of about 0.4 part per billion-a scarcely detectable trace, to be sure, but enough to pique astrobiologists' interest. Over the intervening years, fluid flowing thought it would have initiated chemical reactions that could have destroyed the organic matter - the material discovered may in fact be fragments from bigger molecules.
Some of the new science instruments included on the next Mars rover include an X-ray spectrometer, ultraviolet laser, excited rings of carbon atoms, and a ground-penetrating radar that will allow the space agency to look under the surface of Mars up to 30 feet deep depending on terrain. The rover has returned a lot of fascinating science, but its latest discovery offers the best evidence yet for life on Mars.
NASA scientist Chris Webster confirmed that water has been found on the martian surface and has been present for "a very long time", which points strongly toward a "habitable environment".
Potential contaminants were analyzed and accounted for, so the results are the most conclusive yet.
But the boffins are far from certain the the organic molecules or methane that Curiosity turned up have anything to do with life.
Curiosity found seasonal changes in atmospheric methane on Mars. Before, researchers couldn't understand why the little bit of methane detected in the Martian atmosphere varied. Some of our planet's earliest organisms may have been methanogens - microbes that eat organic molecules and exhale methane gas.
Webster and his colleagues suspect that the methane comes from deep underground, and temperature swings on Mars's surface throttle its flow upward. In a second paper, a group of scientists described methane in the atmosphere of the red planet has been varying. And, of course, there is always the chance that Martian methanogens still slumber in the planet's subsurface even today, periodically awakening during clement periods to produce their gaseous calling-card.
The first, NASA's InSight Lander, will land on November 26 this year and spend two years determine whether the planet is still geologically active.
This work was funded by NASA's Mars Exploration Program for the agency's Science Mission Directorate (SMD) in Washington. For example, scientists want to know if it has "Mars quakes".
"We don't know, but these results tell us we are on the right track"'. "And it makes us more confident that if biomarkers" - or direct evidence of biologic activity - "are there, we might find them".