NASA's rover Curiosity has detected evidence of organic compounds on the surface of Mars, but it is not clear at this stage whether they're the result of contamination or native to the red planet.
Curiosity's Sample Analysis at Mars (SAM) instrument has studied the planet's soil, and found evidence of chlorine, sulphur and water, and hints at organic compounds, reports space news site space.com.
"We really consider this a terrific milestone," says NASA's Paul Mahaffy SAM principal investigator at NASA's Goddard Space Flight Centre.
"We have no definitive detection of Martian organics at this point, but we will keep looking in the diverse environments of Gale Crater… We have to make sure that the carbon and the chlorine are coming from Mars."
The soil was made up of about "half common volcanic minerals and half non-crystalline materials such as glass", NASA said in a release this morning.
"Reactions with other chemicals heated in SAM formed chlorinated methane compounds - one-carbon organics that were detected by the instrument. The chlorine is of Martian origin, but it is possible the carbon may be of Earth origin, carried by Curiosity and detected by SAM's high sensitivity design."
It's this uncertainty which led NASA to downplay rumours in the last couple of weeks that Curiosity had found definitive proof that Mars could support life, such as carbon-based organic compounds.
Curiosity also found water molecules, oxygen and the chlorine compound perchlorate.
"We used almost every part of our science payload examining this drift," says John Grotzinger, Curiosity's project scientist. "The synergies of the instruments and richness of the data sets give us great promise for using them at the mission's main science destination on Mount Sharp."
The announcement was made at a conference in San Francisco this morning.
Curiosity has been operating on the surface of Mars since landing in August. It's the first rover with the ability to scoop up soil and analyse it. It has another two years left on its mission, but if past rovers are any indication, it could be operating long beyond that.