“When we look in the soil we see a bunch of chemicals in there,” said geologist John Grotzinger of Caltech, project scientist for the mission, during a NASA press conference here at the American Geophysical Union conference on Dec 3.

The rover’s instruments found water, sulfur, and chlorine-containing compounds, including chlorinated methane gas — a molecule that contains carbon. Curiosity detected these chemicals by scooping a small sample of Martian dust and heating it up slowly in a small-internal oven and then analyzing the resulting gases that get released. This was one of the first tests of the rover’s Sample Analysis at Mars (SAM) instrument, a microwave-sized machine that allows scientists to conduct experiments on Mars similar to ones they could if they had a sample of Mars soil in a laboratory on Earth. In addition to looking at gases, SAM used a laser spectrometer to determine the isotopes of different atoms in the sample, which could help understand the complicated history of water and other elements on Mars.  Curiosity’s science team thinks that heating the soil sample caused the perchlorates to release chlorine, which readily bonds to other gases such as carbon dioxide, and could have produced the chlorinated methane. We know from previous missions such as Viking and the Phoenix lander that Martian soil contains perchlorate salts, harsh compounds that tend to destroy any organic molecules when heated. Mars’ atmosphere contains carbon dioxide but the team also said that the carbon may simply have been carried from Earth in small amounts since they weren’t able to scrub out every last trace of contamination beforehand.