Martian soil is similar to Hawaii's

Posted by Kate Taylor

NASA's Curiosity rover has finished its first set of tests on the soil sample it scooped up earlier this month and discovered it's a lot like the volcanic soils of Hawaii.

Curiosity used its Chemistry and Mineralogy instrument (CheMin) to obtain the results, which will improve knowledge of past environmental conditions on Mars.

"We had many previous inferences and discussions about the mineralogy of Martian soil," says David Blake, the principal investigator for CheMin.
"Our quantitative results provide refined and in some cases new identifications of the minerals in this first X-ray diffraction analysis on Mars."

Minerals bear the fingerprints of the conditions under which they formed, but the chemical composition of a rock doesn't tell the whole story: for example, diamond and graphite have the same chemical composition, but strikingly different structures and properties.

CheMin uses X-ray diffraction, the standard practice for geologists on Earth, which provides more accurate identifications of minerals than any method previously used on Mars. X-ray diffraction reads minerals' internal structure by recording how their crystals distinctively interact with X-rays.

"Our team is elated with these first results from our instrument," says Blake. "They heighten our anticipation for future CheMin analyses in the months and miles ahead for Curiosity."

The soil sample concerned was scooped up at a patch of dust and sand dubbed Rocknest, and processed through a sieve to exclude particles larger than 0.006 inches. It has at least two components: dust distributed globally in dust storms and fine sand originating more locally.

Unlike the conglomerate rocks Curiosity investigated a few weeks ago, which are several billion years old and indicative of flowing water, the soil material CheMin has analyzed is more representative of modern processes on Mars.

"Much of Mars is covered with dust, and we had an incomplete understanding of its mineralogy," says David Bish, CheMin co-investigator with Indiana University in Bloomington. "We now know it is mineralogically similar to basaltic material, with significant amounts of feldspar, pyroxene and olivine, which was not unexpected. Roughly half the soil is non-crystalline material, such as volcanic glass or products from weathering of the glass."

So far, says Bish, the materials Curiosity has analyzed are consistent with the theory that the deposits in Gale Crater record a transition from a wet to dry environment.

"The ancient rocks, such as the conglomerates, suggest flowing water, while the minerals in the younger soil are consistent with limited interaction with water," he says.