Martian soil hints at water, nutrients

First analysis of Red Planet dirt shows what may be some of the 'requirements for life'

The first analyses of Martian soil scooped up by the robotic arm on NASA’s Mars Phoenix Lander supports the notion that liquid water has flowed on the Red Planet.

SPECIAL DELIVERY This picture documents the delivery of Martian soil to one of four miniature laboratories on the Mars Phoenix Lander. Soil was delivered on June 25, the 30th Martian day, or Sol, of the mission. JPL/NASA, U. of Arizona, Max Planck Institute

SOIL SAMPLE This microscopic image of Martian soil (red, lower image) collected by the robotic arm (pictured holding the soil) on Mars Phoenix Lander shows small clumps of fine, fluffy, red particles collected from a sample called Rosy Red. JPL/NASA, U. of Arizona, Max Planck Institute

A cubic centimeter of Martian soil — about the size of a sugar cube — delivered to one of the miniature laboratories on the lander has revealed several water-soluble elements and inorganic compounds, including sodium, potassium chloride and magnesium, reports Samuel Kounaves of Tufts University in Medford, Mass. Kounaves leads the wet-cell lab experiment, which adds water to samples in order to detect soluble substances.

“We have found what appears to be the requirements — the nutrients — to support life [on Mars], whether in the past, present or future,” he said during a telephone press briefing on June 26. The findings, he added, are one more piece of evidence showing the presence of salts created by “some sort of liquid action at some point in the history of Mars.”

“We were all flabbergasted by the data we got back,” he said. He notes that the composition of material analyzed by the wet-cell laboratory appears strikingly similar to that of the dry valleys in Antarctica on Earth.

The analysis also revealed that the soil is alkaline, between pH 8 and 9, which surprised some researchers, Kounaves noted.

A separate analysis of the first soil sample heated to 1,000° Celsius in one of Phoenix’s miniature ovens — the first time any parcel of a planet other than Earth has been artificially heated to such high temperatures — shows that the grains contain carbon dioxide and water vapor.

“The soil has clearly interacted with water in the past; we don’t know whether that interaction occurred in this area in the northern polar region or might have happened elsewhere and been blown to this area as dust,” said William Boynton of the University of Arizona in Tucson, principal investigator of the team for the Thermal and Evolved Gas Analyzer, or TEGA.

Phoenix landed safely in the planet’s arctic region on May 25, and its signature robotic arm has not yet scooped up any of the ice that resides in the region.

The first soil sample delivered to an oven, nearly two weeks ago, was so clumpy that soil particles clogged a screen over the oven. After vibrating the 30 milligrams or so of soil onto the screen over a period of 4 days, the sample finally went through the screen. The shaking of the sample appears to have caused a short circuit in wiring on one of the other ovens.

In future maneuvers, Phoenix’s robotic arm will tilt and sprinkle soil samples into the ovens to ease particles through the screen and avoid the possibility of other short circuits.

Last week, when scientists commanded the doors to open on another oven, the doors only opened partway. Laboratory studies on Earth indicate that the doors on the other six ovens are likely to have a similar problem, but that material can still pass through. Scientists plan to reserve the ovens with the largest openings for the ice samples. Each of Phoenix’s eight ovens, which make up TEGA, can only be used once.

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