Curiosity rover finds organic compounds, but are they from Mars?

NASA / JPL-Caltech / MSSS

By Alan Boyle

Although NASA's Curiosity rover hasn't yet confirmed the detection of organic compounds on Mars, it's already seeing that the Red Planet's soil contains water and more complex chemicals — including signs of an intriguing compound called perchlorate.

The first soil sample analysis from Curiosity's Sample Analysis at Mars lab, or SAM, was the leadoff topic today at the American Geophysical Union's fall meeting in San Francisco. The findings were eagerly awaited because of rumors that the Curiosity team was on the verge of announcing major findings — and although NASA tamped down expectations, the scientists said they were overjoyed with the first round of analysis.

"We really consider this a terrific milestone," Paul Mahaffy, a NASA researcher who is SAM's lead scientist, said at the AGU briefing.

Mahaffy said in a statement issued by NASA's Jet Propulsion Laboratory that "we have no definitive detection of Martian organics at this point, but we will keep looking in the diverse environments of Gale Crater."

Curiosity landed in Gale Crater on Aug. 5, and since then it's been studying Martian rocks, soil and atmosphere with a suite of 10 scientific instruments. Its two-year, $2.5 billion primary mission is aimed at determining whether conditions in the crater were ever conducive for microbial life.

SAM is a key tool for that mission, because it can cook Martian samples in a mini-oven and then analyze the gases that are given off to identify the compounds contained in the sample. Other instruments — including the Chemistry and Mineralogy instrument, or CheMin — were used as well to study the initial soil samples, collected over the past several weeks from a drift of windblown sand and dust called Rocknest.

This Oct. 31 view from Curiosity's Mars Hand Lens Imager, or MAHLI, shows two of the trenches made by the rover's 1.6-inch-wide (4-centimeter-wide) sampling scoop. The dust and sand from a dune known as Rocknest were fed into Curiosity's onboard labs for analysis.

NASA said CheMin found that the composition of the Rocknest samples was similar to that of soil analyzed by other Mars rovers such as Pathfinder, Spirit and Opportunity — about half common volcanic minerals, and half non-crystalline minerals such as glass. SAM identified other ingredients in much lower concentrations, including water molecules that were apparently bound to the grains of sand and dust. Although the water wouldn't be enough to support any sort of life, the concentration was higher than expected.

SAM also identified a type of perchlorate, a compound that includes oxygen and chlorine. Perchlorate, which was also found by NASA's Phoenix Mars Lander in 2008, is considered a toxic substance and used as an ingredient in rocket fuel on Earth. But scientists say the compound could conceivably serve as an energy source for hardy microbes on Mars. Mahaffy said the particular type of compound detected by Curiosity appeared to be calcium perchlorate, but "we have to study that further."

Reactions with other chemicals in SAM's oven formed chlorinated methane compounds, which geologists consider organic chemicals because they contain carbon and hydrogen. Mahaffy said it was most likely that the chlorine came from a perchlorate-like compound in the soil. However, he said it wasn't yet clear whether the tiny amount of carbon in the compounds came from the Martian soil or was actually brought to Mars from Earth by Curiosity itself.

"We have to be very careful to make sure both the carbon and the chlorine are coming from Mars," he told reporters. More >>