June 14, 2008

NASA’s Phoenix Gets the Dirt on Mars

The National Aeronautics and Space Administration's Phoenix probe scraped the frigid Martian ground with its robotic arm on Friday and revealed what looks like a layer of ice or perhaps bright salt just beneath the red soil.

The lander also sent back its first microscopic pictures gathered from a scoopful of Martian soil, showing a mix of tiny red particles, minerals and glassy volcanic sand.

The findings suggest that Phoenix has landed in a good place to carry out its scientific mission of detailing the history of water and life-related compounds near the north pole of Mars. Mission scientists hope to determine whether the ice is ancient or formed recently.

If the ice is relatively young _ less than a hundred thousand years old or so _ it could mean the planet has a fluctuating climate, with brief warmer periods when the ice melts and then re-freezes. Such an active climate might increase the odds that microbial life has survived beneath the frozen surface of Earth's neighbor.

"On Earth, the polar regions preserve traces of climate change, and even preserve signs of life and organic material," Phoenix team leader Peter Smith said at a news briefing Friday.

Smith noted that not everyone on the team agrees that the white material beneath the soil is ice, though measurements taken from orbit make it all but certain that a layer of ice exists close to the surface at the Phoenix landing site.

Earthbound mission leaders spent most of the last week figuring out how to maneuver soil into one of the probe's onboard chemical analysis ovens. The soil was surprisingly clumpy, and at first it would not sift through the oven's filter screen.

That stickiness was evident in the microscopic photos of the soil that Phoenix beamed back Friday. Researchers are not sure why the soil particles clump together so well, but it may be because of electrostatic forces or a side effect of ice in the soil evaporating into the atmosphere.

"This is obviously a very sticky material, right down to the finest scale," said Tom Pike, a leader of the Phoenix microscopic imaging team.

On Wednesday the scientists succeeded in shaking a soil sample through the oven filter, and they hope to complete a chemical analysis of it over the next week. The team plans to analyze the soil in layers, studying the suspected ice layer last of all.

The chemical composition of the ice may hold a key to understanding how the polar regions evolved on Mars.

If the ice contains ratios of isotopes similar to what is present in the Martian atmosphere, that would imply the ice formed relatively recently. But if the ratios in ice and atmosphere diverge, that could mean the ice formed billions of years ago, when the Martian atmosphere had a different composition than today.

Phoenix is the first Mars probe since the Viking missions of the 1970s to dig into the alien soil and study it with onboard chemistry labs. The lander carries two kinds of chemical analysis devices and two microscopes that are the most powerful NASA has ever sent to another world.

"We're not going to be able to find life, but whether the environment would be conducive to life," said Leslie Tamppari, the Phoenix mission's lead scientist who's also with NASA's Jet Propulsion Laboratory in Pasadena, Calif.


(Chicago Tribune correspondent Michael Martinez contributed to this report from Los Angeles.)


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