In the meantime, Curiosity will take a break over the Thanksgiving holiday, during which scientists will use the rover's camera to look for future routes and targets for investigation.
"This data is one for the history books," NASA Jet Propulsion Laboratory scientist John Grotzinger recently told National Public Radio, while adding that he could not divulge more until scientists had a better chance to vet the data. Hypotheses have ranged from a discovery of complex organic matter to chemicals indicating the presence of water.
According to Grotzinger, NASA's Sample Analysis at Mars (SAM) was the tool that facilitated the discovery. SAM is a hypersensitive set of three instruments -- a quadrupole mass spectrometer, a gas chromatograph and a tunable laser spectrometer -- that process and analyze soil samples in search of compounds containing carbon and other elements associated with life.
[ Learn more about the Mars mission. See NASA Curiosity Visual Tour: Mars, Revealed. ]
SAM is the largest tool on Curiosity, weighing in at 88 pounds. The tool's mass spectrometer separates compounds and elements by mass to help scientists identify them, while the chromatograph vaporizes samples and analyzes the resulting gasses, and the laser spectrometer measures isotopes of carbon, hydrogen and oxygen in gasses.
"Because these compounds are essential to life as we know it, their relative abundances will be an essential piece of information for evaluating whether Mars could have supported life in the past or present," NASA says in an online description of SAM's mission online.
NASA sent SAM to Mars with five specific goals, all of which aim to address questions about habitability on Mars. These goals include surveying carbon sources on Mars, searching for organic compounds, revealing the state of isotopes on Mars that are important for life as we know it on Earth, determining Mars' atmospheric composition and measuring other gases in order to "better constrain models of atmospheric and climatic evolution."
Curiosity recently spent six weeks testing its soil sampling tools at a sand dune that NASA named Rocknest. The $2.5 billion Curiosity is on a broader two-year mission to investigate Mars' present or past habitability after landing in August in the Red Planet's Gale Crater -- a site that, according to NASA analysis of satellite imagery, was historically covered with water.
NASA first used SAM's soil sample tool with soil from Rocknest on November 9, and followed that sampling with two days of analysis on the sample. In a statement issued November 13, SAM principal investigator Paul Mahaffy indicated that the sample yielded "good data," but did not tip his hand as to what that data portended.
While the discovery of organic compounds would be significant, as previous missions have not found them on Mars, NASA officials have previously said in interviews that they expect that Curiosity would find organic materials. The presence of organics would not necessarily indicate past or present presence of life on Mars: For example, organics can be found on meteorites, and methane can be produced by abiotic processes.
NASA plans to announce the news at the fall meeting of the American Geophysical Union, which takes place December 3 to 7 in San Francisco. NASA scientists have already used SAM to analyze Mars' atmosphere, finding little evidence of methane in the atmosphere despite an earlier false alarm.