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Pay Dirt: Martian Soil Fit for Earthly Life

Phoenix finds alkaline soil with plenty of minerals
soil sample



Color: NASA/JPL-Caltech/University of Arizona/Max Planck Institute

Martian soil around NASA's Phoenix Lander is slightly alkaline and has enough different minerals that it could support Earthly plants and—more to the point—microbes beneath the Martian surface, according to the first results from the probe's wet chemistry experiment released today.

Mission scientists say the soil has a pH between 8 and 9, which places it somewhere around seawater or baking soda in alkalinity. It also contains the minerals magnesium, sodium, potassium and chloride. Further analysis is expected to reveal whether it contains other chemicals such as nitrogen and sulfates. The finding implies that life could indeed survive below the surface, where it would be protected from harmful ultraviolet rays and harsh oxidants that might accumulate on the top layer of soil.

Michael Hecht, lead researcher on Phoenix's Microscopy, Electrochemistry and Conductivity Analyzer (MECA) instrument, at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said it would be safe, if gritty, to sprinkle a spoonful of the soil on your breakfast cereal.

"If you had it on Earth, you could grow something, no problem," MECA co-investigator Samuel Kounaves, chemist at Tufts University, said during a news conference at the University of Arizona in Tucson.

Were astronauts to set up a greenhouse on Mars, Hecht said, they might be able to grow plants that thrive in basic soil, such as asparagus, green beans and turnips; not so strawberries, blueberries and other fruit, however, that require more acidic soil. (So much for a healthy breakfast.)

The results were announced a day after Phoenix's robot arm placed about 0.06 cubic inch (one cubic centimeter) of soil, skimmed from the top inch of dirt at Wonderland, the probe's current dig site, into MECA's wet chemistry experiment, which melted a small block of ice brought from Earth and then dropped the soil into the water for analysis.

"We're making mud, we're stirring it up, we're measuring it with sensors," Hecht said.

The question is whether similar mud exists or previously existed at the site. Coming closer to an answer, Phoenix scientists reported they had finished heating their first soil sample with another instrument, the Thermal and Evolved-Gas Analyzer (TEGA).

As expected, they did not find any evidence of ice; the sample came from the top layer of soil, where frozen ice would have quickly vaporized, as it seemed to do last week.

But TEGA did produce a whiff of water vapor as well as carbon dioxide, implying that the soil was once exposed to liquid water. This confirms earlier findings from Phoenix's fellow surface explorers—the Mars rovers Spirit and Opportunity, still operating at other locations on the Red Planet, have turned up evidence of minerals formed in the presence of water.

Phoenix scientists hope to use such data to determine where and when Martian life might find (or had found) a moist refuge. They are not certain whether the soil baked in TEGA has long been at its present location or whether winds may have blown it there from elsewhere on the planet.

The findings also do not yet paint a picture of the soil at different depths and locations. "It's only part of the story," Kounaves said. "We'll have to see the rest of the story."

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