Scientists say they know white stuff was frozen water because it vanished. The scientists behind NASA’s Phoenix Mars Lander mission now know that they had their first close-up look at Martian ice — because it has vanished from the picture. Days ago, streaks and bits of whitish material were spotted at the bottom of a trench dug by the lander’s robotic scoop, leading scientists to speculate that the stuff was either ice or salt. An initial chemical analysis was inconclusive, but scientists said they could tell by seeing if the material disappeared after exposure to the thin Martian atmosphere.

Under such conditions, water ice would turn directly into vapor rather than melting into liquid, in a process known as sublimation. When scientists compared Sunday’s pictures with imagery captured early Thursday, dice-sized crumbs of the white material were clearly missing.

“It must be ice,” the University of Arizona’s Peter Smith, principal investigator for the Phoenix mission, said Thursday in a NASA status report. “These little clumps completely disappearing over the course of a few days, that is perfect evidence that it’s ice. There had been some question whether the bright material was salt. Salt can’t do that.”

A larger vein of white material is still visible in the trench, which scientists have dubbed “Dodo-Goldilocks.”

The Phoenix team reported that the lander’s robotic scoop hit a hard surface while it was digging in a different trench early Thursday, and they speculated that the surface could represent a layer of ice. The new trench is nicknamed “Snow White 2,” and lies right next to the Snow White 1 trench in an area that has been set aside for scientific study.

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

After three attempts to dig further into the surface, the arm went into a holding position. Such an action is expected when the robotic arm comes upon a hard surface, NASA said.

One of the primary aims of Phoenix’s mission is to determine whether the layers of soil and ice in Mars’ north polar region contain the chemical building blocks of life. The lander can cook soil samples in its ovens and analyze the composition of the gases given off. The probe is not designed to detect life itself, however.

Posted by Zoov on 20 Jun 2008 02:48 am
Filed Under: Sci-Tech |