June 7 (UPI) -- NASA's Curiosity rover has found organic molecules in ancient sedimentary rock collected from Mars' surface. The rover's labs also confirmed seasonal fluctuations of methane in the Martian atmosphere.
Taken together, the discoveries suggest Mars once hosted ancient life.
"With these new findings, Mars is telling us to stay the course and keep searching for evidence of life," Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters, said in a news release. "I'm confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet."
The Martian climate is too dry and the atmosphere is too thin, leaving the surface exposed to significant amounts of radiation, for Mars to host life today. But many scientists believe the Red Planet could have hosted simple life forms several million years ago, when it was cooler, wetter and had a thicker atmospheric buffer.
Using their fleet of Martian rovers and satellites, scientists have been searching for geochemical signs of ancient life. The latest findings offer additional clues for where signs of ancient life might be hiding.
"Finding ancient organic molecules in the top five centimeters 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," said Jen Eigenbrode, Curiosity scientist at NASA's Goddard Space Flight Center.
Eigenbrode and her colleagues described the discovery of organic compounds in one of two new papers published Thursday in the journal Science. A second paper details the discovery of mercury fluctuations found in Mars' atmosphere.
Through three years of testing, Curiosity's lab analysis has revealed seasonal variations in the amount of methane in Martian air. The variations could be explained by interactions between water and rocks, but scientists say they can't rule out a biological cause.
The organic molecules identified by Curiosity and NASA scientists were found in samples of mudstone collected from the ancient lakebed inside Gale Crater. The rover's internal laboratory heated the powdered rock sample to 900 degrees Fahrenheit to release organic molecules.
The lab, nicknamed SAM, identified several fragments of larger organic molecules that don't easily vaporize. SAM also measured traces of sulfur, which may have helped preserve the organic molecules.
Curiosity's latest discoveries offer a blueprint for NASA's future Martian landers -- a map for where to look for more signs of ancient life.