Ice Found By Phoenix

"It must be ice." That's the conclusion of Peter Smith, principal investigator of the Mars Phoenix Lander. He based that conclusion on a Martian disappearing act. The Phoenix robotic arm dug a trench in the soil a few days ago and uncovered clumps of whitish material. Scientists couldn't decide whether the stuff was salt or water ice. Imaging the trench again a few days later, after the clumps had been exposed to the sun's heating-- the clumps were gone. Water ice vaporizes on Mars when exposed to heat. Salt does not.

So, Phoenix has already made a major discovery. Water, in the form of ice, seems to exist over much of subsurface Mars. Earlier, NASA's rovers had found evidence of water nearer the equator. Easily accessible water bodes well for future human exploration and colonization of the planet.

Of course, fairly abundant water also leaves open the possibility of life. Discovering evidence of past or current life on Mars may be the only bigger discovery Phoenix could make.