Perchlorates: Mars Chemical Changes Search for Red Planet Life

The Curiosity Rover took this composite self-portrait in the Rocknest sand patch on Mars. Tests of soil at the site suggest that troublesome chemicals called perchlorates are common on the Red Planet.

Credit: NASA

Astronauts sent to Mars on future space missions will have to contend with the toxic and explosive chemical known as perchlorate that's widespread in Red Planet dirt.

Perchlorates have already proved to be problematic for researchers using robotic rovers to hunt for possible traces of Martian life, a new study has found.

As part of its science mission, NASA's Mars rover Curiosity heats up scoops of Red Planet dirt to test for organic carbon compounds — the building blocks of life on Earth.

But that heat can cause perchlorates in soil samples to set off a chemical reaction that destroys organics, researchers discovered.

Daniel Glavin

"The presence of perchlorates isn't good news for some of the techniques currently being used with Curiosity," study lead author Daniel Glavin, an astrobiologist at NASA’s Goddard Space Flight Center in Greenbelt, Md., said in a statement.

"This may change the way we search for organics in the future on Mars."

Perchlorates, which are salts comprised of chlorine and oxygen, were first detected in Martian polar soil by NASA's Phoenix lander in May 2008.

More recently, Curiosity found perchlorates while trekking around the Rocknest sand dune in November 2012.

Curiosity's Sample Analysis at Mars (SAM) system uses a pyrolysis gas chromatograph mass spectrometer, which is an instrument that breaks soil down into its chemical components and measures the concentration of each type of molecule.

But when perchlorates in these soil samples are heated above 392 degrees Fahrenheit (200 degrees Celsius), they release pure oxygen, the researchers say.

This oxygen then causes organic molecules in the sample to combust into carbon dioxide.


However, Glavin said not all of the organic carbon would be destroyed in this reaction; some might be preserved inside more heat-resistant materials, or the molecules could possibly be detected before the breakdown of perchlorates.

Scientists might be able to account for the organic carbon that has combusted if they assume a certain baseline of perchlorate in Martian dirt, he added.

The recent findings at Rocknest could help scientists establish this baseline.

"It will be absolutely critical as we move on to other samples to compare them to the Rocknest dune to infer the presence or absence of Martian organic material," Glavin said in a statement.