Curiosity gets the dirt on Mars

Whiffs of chemicals found in rocket fuel, a dark pyramid that resembles rare volcanic rocks on Earth and glassy particles bearing traces of water are among the Curiosity rover’s finds in its first chemical investigation of Martian dirt.

“This is the first time we’ve known precisely and definitively what this stuff is made of,” says astrobiologist David Blake of the NASA Ames Research Center in Moffett Field, Calif. He and his colleagues report the results of the analysis September 26 in Science.

In samples scooped from Martian dust, Blake and his colleagues found a mix of crystals from volcanic rocks plus glassy particles. Researchers discovered the blend by bombarding soil with radioactive alpha particles and using the energy signatures bounced back to identify the soil’s chemical contents.

The scientists also used a shoe box–sized instrument at the front of the rover that identifies minerals based on how their crystal structures diffract, or bend, X-rays.

“The exciting part for many of us is getting the X-ray diffraction data,” says mineralogist David Bish of Indiana University. An X-ray diffraction instrument used to be the size of a large refrigerator, he explains. But he and his colleagues figured out how to miniaturize the machine for Curiosity, in part by borrowing a tiny image recording device from cell phones.

To further dissect the dirt, geochemist Laurie Leshin of Rensselaer Polytechnic Institute in Troy, N.Y., and colleagues fired up a microwave-sized instrument in the belly of the rover. There, scientists heated a tiny pile of soil to about 835° Celsius and examined the gases that came off.

They found that the sample contained around 2 percent water, probably hidden in the glassy particles. The analysis also found a variety of chlorine compounds, including perchlorate, a toxic component of rocket fuel, which could complicate future plans for humans to live and work on Mars. Both the water and the chlorine probably come from the atmosphere, Leshin explains. “The dirt is acting as a bit of a sponge,” she says. So far, they haven’t found any organic compounds that might signal life.

Last, researchers examined a black, pyramid-shaped boulder about 50 centimeters tall, which they dubbed Jake_M after NASA engineer Jacob “Jake” Matijevic, who passed away in 2012.

Jake_M is unlike any Martian rock ever examined, and most closely resembles a rare type of lava found on islands on Earth. “It’s not just that it looks sort of like it,” says geologist Edward Stolper of Caltech, “you would have a hard time telling them apart.” The find gives some hints about how rocks have formed on Mars, he says.

“The question is: ‘Will we find another one?’ ”