Organic Matter May be on Mars: Scientists Discover Martian Soils Hold Carbon

Could there be organic matter on Mars? The organic matter that was recently detected by NASA's rover Curiosity probably isn't due to contamination brought from Earth, as originally thought. Scientists now suggest that the gaseous chlorinated organic compound, chloromethane, may come from the Martian soil.

Scientists have long debated whether or not there's organic matter on Mars, which is an essential requirement for life on the planet. That's why NASA's Mars Curiosity rover has been conducting investigations on Martian soil. When the rover heated soil samples, it detected simple organic molecules with its onboard measurement systems. One of the substances detected in particular was chloromethane, which contains carbon, hydrogen and chlorine atoms.  Yet at the time it was detected, NASA experts believed that the compound could have been formed during the heating experiments by a reaction between perchlorates in Martian soil and an onboard chemical that may have contaminated the sample.

Yet it turns out that this contamination may not have occurred. Scientists have now examined whether there could be another explanation for the observations of chloromethane on Mars. They assumed that the gaseous chlorinated organic compound was actually from the Martian soil, but that its carbon and hydrogen were produced by meteorites.

In order to see if this was possible, the scientists examined samples from a 4.6 billion-year-old meteorite that fell on Earth in 1969. The meteorite material contained two percent carbon. A relatively large amount of micrometeorites with a similar composition to this one are thougth to fall on the surface of Mars each year.

"The ratio of heavy to light carbon and hydrogen atoms, known as the isotopic fingerprint of gas, clearly shows that the organic material has an extraterrestrial origin," said Frank Keppler, one of the researchers, in a news release.  "Hence chloromethane which was found by the two separate Mars missions could be formed by the Martian soil, and the carbon and hydrogen would have their origin in the micrometeorites that rain down on Mars. However, it cannot be ruled out that microorganisms which might have been living on the planet some time ago might have provided a fraction of the organic matter."

The findings are published in the journal Scientific Reports.