IU Bloomington geologist reports results of Mars mineralogy investigation

  • Sept. 26, 2013


BLOOMINGTON, Ind. -- The first mineralogy experiments by the Mars Science Lab on board the Curiosity rover confirm the presence of basaltic minerals similar to those found on Earth at Mauna Kea volcano in Hawaii, according to research results published online today by the journal Science.

Indiana University Bloomington geologist David Bish is the lead author of one of five papers published online today by the journal Science and detailing the results of sophisticated mineralogical and geochemical measurements. He is a co-author of two of the other articles. Preliminary results were reported in a NASA news conference last fall.

The articles describe analyses of samples taken by Curiosity from a windblown drift of dust and sand in Gale Crater, which the scientists dubbed Rocknest. They provide new information relevant to understanding Mars, from its deep history to present-day interactions between soil and atmosphere.

Bish, the Haydn Murray Chair of Applied Clay Mineralogy in the Department of Geological Sciences in the College of Arts and Sciences, is co-investigator for the Chemistry and Mineralogy experiment, or CheMin, which uses a portable X-ray diffraction instrument to investigate the structure of minerals. X-ray diffraction is the preferred and most definitive method for determining the nature of crystalline phases, such as minerals, in solid samples.

Juergen Schieber, an IU Bloomington professor of geological sciences, is also part of the Mars Science Lab project. An expert in sedimentary geology, he is part of the team analyzing data from the Mars Hand Lens Imager, which shows textures, colors and shapes of target materials on Mars' surface.

In what Bish calls a "happy coincidence," the recent mineralogical analysis was undertaken in the year of the 100th anniversary of the discovery of X-ray diffraction by the German physicist Max von Laue, who won the 1914 Nobel Prize in Physics for the discovery.

The Rocknest samples include both crystalline minerals and glassy or amorphous material. X-ray diffraction of the crystalline material revealed the minerals plagioclase feldspar, forsteritic olivine, augite and pigeonite, with very small amounts of other minerals possibly present.

"The minerals we found on Mars are typical of the kind of minerals you find in basalt -- which isn't surprising, because the surface of Mars is mostly basaltic," Bish said.

The analysis gives scientists a better understanding of the windblown soil and dust that covers much of Mars and often obscures the surface, giving the planet its reddish color. Bish said the materials are old, even by geological standards, and have undergone no apparent alteration through interaction with water -- supporting the idea that Mars has been a dry planet for at least hundreds of millions of years.

Also significant was what X-ray diffraction did not find: No evidence of water molecules, or even hydrogen, in the crystalline material; and no evidence of clay minerals. The latter finding was a surprise, because data from other investigations had indicated clay minerals were present in Gale Crater.

"The presence of clay minerals would indicate an environment that once was wet, and potentially habitable," Bish said. "And we did not find that."

He said it's possible that clay minerals are present but the basaltic minerals "overwhelm everything else" in the analysis, or that clay minerals are there but below the detection limit. Research reported by NASA last week found no evidence of methane on Mars, also a surprise and a setback to hopes of finding current microbial life on the planet.

The research published today did indicate, however, that water molecules are present in the Martian dust, apparently in the amorphous or glassy material that Bish said was analogous to powdered obsidian. Heating Rocknest samples inside Curiosity released common gases including H2O, carbon dioxide, sulfur dioxide and oxygen. Measurements by the rover's Sample Analysis at Mars instrument established the dust as about 2 percent H2O.

Other Curiosity research, including analysis of rocks and examination of sediments, has suggested Mars was quite wet and included flowing water in the ancient past.

Bish said analysis of the Rocknest materials continues, and additional findings have been submitted for publication. Meanwhile, the rover is driving toward Mount Sharp, an 18,000-foot peak within Gale Crater, where researchers hope to find further evidence of past habitable environments.

"It's a research project," Bish said. "There's nothing about this project that's by the cook book. We're constantly learning new ways, better ways, to analyze the data. We're continuing to analyze our existing data and extract as much information as possible from that data."

Curiosity landed on Mars Aug. 6, 2012, and the mission is expected to continue through 2014. 

Related Links

Curiosity rover at Rocknest

This picture, assembled from high-resolution images taken by the Mars Hand Lens Imager, shows the Curiosity rover at Rocknest. | Photo by NASA image

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Mars X-ray diffraction data

This graphic shows results of the first X-ray diffraction analysis of Martian soil by the Chemistry and Mineralogy experiment, or CheMin, on NASA's Curiosity rover. | Photo by NASA image

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