A week after downplaying reports of a major discovery on Mars, NASA on Monday announced that the rover Curiosity has found complex chemicals on the surface of the planet.
The space agency noted that it has yet to find definitive evidence of organic matter on Mars.
NASA last week had said an NPR.com report that it was working to confirm a significant discovery by Curiosity was untrue.
During a press conference, Paul Mahaffy, a Curiosity principal investigator, said: "We have no definitive detection of Martian organics at this point, but we will keep looking in the diverse environments of Gale Crater."
Curiosity, the first NASA rover to scoop Martian soil into onboard analytical instruments, has found what agency scientists are calling a complex chemistry within the Martian soil, NASA said.
The analyzed soil came from a drift of windblown dust and sand that scientists dubbed "Rocknest." The site where the sand was found lies in a relatively flat part of Gale Crater where the rover landed in August.
Curiosity's scientific instruments are checking the soil for organic compounds, such as carbon-containing chemicals that can be a source for organic life, officials said.
The rover, on a two-year mission to discover whether Mars can or has ever been able to support life, this fall discovered evidence of a vigorous, thousand-year water flow on Mars.
NASA now is hoping to find other pieces of the Mars puzzle.
For instance, one of the rover's instruments has tentatively identified perchlorate, an oxygen and chlorine compound. This chemical had been found in 2008 in arctic Martian soil by NASA's Phoenix Lander, a predecessor to Curiosity.
Perchlorate, which is used in pyrotechnics and rocket fuel, could be used as an energy source for Martian microbes. Scientists are going to continue studying the chemical.
Scientists also said the instruments were used to identify other chemicals in the soil, including chlorinated methane compounds, which are categorized as organic chemicals since they contain carbon.
Paul Mahaffy, a lead scientist on the Curiosity team, noted that while part of the compound likely is native to Mars, the carbon in it could have been brought there from earth onboard Curiosity. Scientists are still studying the discovery.
"We used almost every part of our science payload examining this drift," said Grotzinger.
