NASA's Mars rover Curiosity has discovered complex chemistry on the Red Planet after, as well as hints of long-sought organic compounds that could aid primitive life, scientists announced today (Dec. 3).

The Curiosity rover found evidence of chlorine, sulfur and water in Mars dirt studied by its onboard laboratory, as well as organic compounds (chemicals containing carbon) inside its Sample Analysis at Mars instrument. However, the science team can't yet be sure whether these compounds truly come from Mars, or arise from contamination transported to the Red Planet onboard Curiosity.

"SAM has no definitive detection to report of organic compounds," Paul Mahaffy, SAM principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Md., said during a press conference at the annual meeting of the American Geophysical Union in San Francisco.

"Even though instrument detected organic compounds, first of all we have to determine whether they're indigenous to Mars," said John Grotzinger, Curiosity's project scientist.

The announcement came after recent rumors—which NASA attempted to dampen last week — that Curiosity had made a huge discovery on Mars.