Curiosity's experiments on Martian soil may be inadvertently eliminating traces of organics, British researchers reported this week. One of the compounds the rover is on the lookout for is jarosite, a mineral associated with conditions potentially suitable for life. Curiosity tests for jarosite and other interesting substances by flash-heating soil samples, watching for telltale signs of certain elements.
Tests conducted by a team at Imperial College London show that this heating process may cause the jarosite to break up and give off free oxygen — which can then destroy organic compounds in the soil. Essentially, the testing method could eliminate what it's looking for in the process.
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"The destructive properties of some iron sulphates and perchlorate to organic matter may explain why current and previous missions have so far offered no conclusive evidence of organic matter preserved on Mars' surface," Imperial College's Mark Sephton, the study's lead author, explained in a news release. "This is despite the fact that scientists have known from previous studies that organic compounds have been delivered to Mars via comets, meteorites and interplanetary dust throughout its history."
A member of the rover science team acknowledged that this is an issue, but assured NBC News in an email that the jarosite issue has been anticipated and controlled for.
"Certainly there is the potential for any sample that releases an oxidant such as O2 on heating to combust organic compounds and turn them into carbon dioxide," said Paul Mahaffy, chief of the Planetary Environments Laboratory at NASA's Goddard Space Flight Center. "This is in line with our extensive lab experiments that show that often organic compounds are able to escape on heating from a variety of samples including some that contain jarosite."
The jarosite may break up some of the organics in the soil, but it's probably not going to get all of them, and only a trace amount needs to escape to be detected.
Mahaffy also pointed out that the rover also carries a wet-chemistry experiment that avoids this particular issue. "When we have this experiment fully tested on our equipment in the laboratory and find the right sample on Mars we plan to utilize this experiment," he said.