June 20, 2008
NASA Confirms Ice Found on Mars
Scientists rejoiced on Friday after learning NASA's Phoenix Lander dug up underground ice on the plains surrounding the North Pole of Mars, but said they have more to accomplish before the summer ends.
Using mini chemistry labs on the spacecraft, they hope to determine whether the frozen water excavated with the lander's robot arm, as well as nearby soil, contains the chemical building blocks of life.
Peter Smith, the University of Arizona researcher who leads the Phoenix mission's science team, announced late Thursday that colleagues were convinced eight pieces of white dice-sized soil crumbs dug up Sunday were ice, not salt deposits or quartz as some had speculated. The claim was based on photos taken four days apart.
The crumbs in the earlier image were no longer present in the photographs that reached the earth on Thursday, leading scientists to conclude the crumbs were ice that evaporated into the thin Martian atmosphere.
"To me personally, it was such a thrill to find ice under the lander," Smith told a news briefing on Friday. "I'm just sitting on the edge of my chair waiting to see what (the two chemistry labs) can tell us about the soil."
Phoenix touched down on Mars on May 25 as the centerpiece of a $457 million, 90-day mission to determine whether the cold, dry planet was once warm and wet enough to host some form of life. As the spacecraft's cameras came to life in the days after the landing, the imagers spotted what appeared to be a layer of ice exposed by thruster exhaust during the touchdown just a few inches below the surface.
More of the gleaming material was exposed two to three inches below the top layer of soil as the nearly eight-foot-long robot arm began to dig a network of trenches close to the probe. However, until the "before and after" images were examined by the Phoenix science team on Thursday, the bright material could have been a clump of ice, or light colored rocks or mineral deposits.
The cold temperatures and very thin atmosphere on Mars are just right for frozen water to vaporize into the air without becoming a liquid first, just like a block of "dry ice," or frozen carbon dioxide, evaporates on Earth.
"The images are the final proof. Salt does not behave like that," Mark Lemmon, a Texas A&M University astronomer who leads the mission's surface imager team, said Friday. "I'm very excited. We can reach out and touch it, we can sample it and use our instruments to sniff it."
The discovery of underground frozen water at the Martian north and south poles was made by NASA's Mars Odyssey, an orbital spacecraft that has been circling the Red Planet since 2001. The finding was based on the high hydrogen concentrations detected by Odyssey's instruments. Scientists concluded the source of the hydrogen was best explained by buried ice.
Over the coming weeks, the Phoenix science team plans to heat and dissolve samples of the soil and ice collected by the probe's robot arm in two mini chemistry labs. The labs are equipped to characterize the mineral and chemical makeup of the samples.
Scientists will be looking for evidence of carbon-based compounds that form the building blocks of life and evidence of minerals that form in water, a sign the ice on Mars was not always frozen. The carbon compounds scientists seek are vulnerable to the high levels of ultraviolet radiation from the sun that reach the Martian surface.
Smith said Friday that scientists will analyze the soil before the ice. The soil samples will come from the surface of the landing site and below ground and just on top of the ice. The ice is so hard "” as brittle as concrete "” that it must be collected either with drilling or scraping tools on the robot arm.
Neither the drilling or shaping devices have made test runs since the landing.
"We promised ourselves that we will have answers by the end of August," said Smith "But we all want them sooner."
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