Phoenix Hits Ice

Mysterious white marble-sized chunks of material lying in a trench dug in martian soil by the Phoenix lander last week have disappeared over the past four days, confirming speculations that the lander's scoop had unearthed ice.

??"It is with great pride and lot of joy that we announce we have proof that the hard white material is water ice," Peter Smith, principal investigator for the Phoenix mission at the University of Arizona, said at a press conference on June 20.

Scientists had postulated that the recently uncovered stark-white substance could be either salts or ice. But the images, taken on the 20th and 24th martian days of Phoenix's operation, show that patches of the white substance have shrunk and chunks are missing.

"Salt does not behave like that," said Texas A&M's Mark Lemmon, lead scientist for the craft's surface stereo imager, at the press conference. The chunks, he added, have "literally disappeared."

After being unearthed by Phoenix's robotic arm, the lumps sat exposed in the cold dry martian environment, where they sublimated or became water vapor, Lemmon explained.

Phoenix will continue to dig in several trenches, which team scientists have given whimsical fairy-tale-themed names, such as "Goldilocks," "Wonderland," and "Snow White."?? Over the next couple of weeks, the team will analyze soil samples, using Phoenix's mass spectrometer and onboard wet chemistry lab.

The goal of the mission is to study the possible ancient role of water near Mars's north pole, a region where NASA's Mars Odyssey spacecraft detected fields of subsurface ice several years ago.