Saturday, June 21, 2008

Scientists rejoiced Friday after the Phoenix Mars lander confirmed their long-held belief that ice is hiding under the surface in the Red Planet’s northern region.

The lander’s robotic arm started digging trenches into Martian soil after touching down near the planet’s north pole on May 25, revealing a white substance that scientists had said could be either salt or ice.

Phoenix flexed its arm again to enlarge a trench Sunday. It then took pictures of eight bright bits of material the size of dice inside the hole, which scientists dubbed “Dodo-Goldilocks.”

When the lander took new photographs of the trench four days later on Thursday, the material had vanished, settling the debate about whether it was salt or ice.

Scientists at the Jet Propulsion Laboratory in Pasadena, Calif., concluded the material was frozen water that evaporated when exposed to the sun. Salt would not have reacted that way, scientists said.

“We found what we were looking for,” Phoenix science team member Mark Lemmon said during a news conference. “We came to this site because we were expected to find water ice.”

Scientists believed a vast sheet of ice was hiding in the planet’s north pole after NASA’s Mars Odyssey surveyed it in 2002.

“If you had a big broom and swept this area off, we are on an ice sheet,” said Phoenix principal investigator Peter Smith of the University of Arizona at Tucson.

“We have found the proof that we have been seeking that showed that this bright material really is water ice, and not another substance,” Mr. Smith said.

“Now we know for sure that we are on an icy surface and we can really meet the science goal of our mission at the highest level,” he said.

Besides evidence of water, the three-month Phoenix mission is also hoping to find life-supporting organic minerals in the polar region.

The probe is equipped with oven-like instruments that can melt ice collected by the robotic arm and analyze the water.

The trick, Mr. Smith said, is for Phoenix to move ice samples fast enough from the ground into one of the lander’s eight ovens. It has to be accomplished within 30 minutes, before the ice evaporates in the atmosphere.

“Just the fact that there’s ice there doesn’t tell you if it’s habitable,” he said.

“With ice and no food it’s not a habitable zone. We don’t eat rocks. We have to have carbon chain materials that we ingest into our bodies to create new cells and give us energy. That’s what we eat and that’s what has to be there if you’re going to have a habitable zone on Mars.”

Mars is currently too cold for liquid water, but it is possible that in the distant past the polar regions were warmer, scientists posit.

Phoenix’s robotic arm made contact in another trench Thursday with a hard surface scientists believe could be an icy layer.

“We have dug a trench and uncovered a hard layer at the same depth as the ice layer in our other trench,” said Ray Arvidson of Washington University in St. Louis, co-investigator for the robotic arm.

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