Visions of dirt

Lander captures picture of Martian soil

The Phoenix Lander has sent back the most-detailed view of the Red Planet’s soil to date.

UP CLOSE AND PERSONAL This image, taken by the optical microscope on the Phoenix Lander, shows a magnified view and three zoomed-in portions of Martian soil particles. The left zoom box shows a composite particle. The top of the particle has a green tinge, indicating the mineral olivine. The bottom of the particle has been reimaged at a different focus position in black and white; the middle zoom box shows that this is a clump of finer particles. The right zoom box shows a black, smooth soil particle. Scientists think it is a glassy, volcanic soil grain. NASA, JPL-Caltech, Univ. of Ariz.

Not since the Viking Landers, in the 1970s, has a spacecraft scooped and tested Martian dirt to learn more about the composition of Mars, said Peter Smith, the mission’s principal investigator, in a news conference Friday.

On June 12, using an optical microscope inside one the lander’s instruments, the Phoenix science team took the highest resolution image of individual soil grains. The team can now begin to identify, in great detail, the minerals making up the north polar region of Mars.

The bigger particles are a little less than the diameter of a human hair, about 50 micrometers in size, said Tom Pike, a coinvestigator from Imperial College London who used the Microscopy, Electrochemistry and Conductivity Analyzer or MECA, which houses the optical microscope.

Going on color alone, he said, the team has detected the mineral olivine, which has a greenish tinge. In the same image, the team saw the characteristic iron-enriched reddish, orange soil grains that cover all of Mars. The scientists even picked out smooth, black particles that indicate the presence of volcanic glass.

“What we are looking at is the past history of Martian soil,” Pike said. “The black, glassy material has been there for millions or billions of years, and the iron-enriched grains tell about weathering that has gone on for that period of time.”

The new microscopic images are the first scientific evidence from which the team can draw conclusions about the planet’s polar soil. Early next week, the lander will transmit data from the spacecraft’s other instruments to reveal information about the region’s salt and ice content.

“Stay tuned,” Smith said, “and we will see what is under the surface.”

Ashley Yeager is the associate news editor at Science News. She has worked at The Scientist, the Simons Foundation, Duke University and the W.M. Keck Observatory, and was the web producer for Science News from 2013 to 2015. She has a bachelor’s degree in journalism from the University of Tennessee, Knoxville, and a master’s degree in science writing from MIT.

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