cathector writes "
wow, if they found water ice on mars just a few inches below where the lander uh landed, the place must be lousy with the stuff !
Scientists have figured out the mysterious white substance unearthed by NASA's Phoenix lander on Mars. It's frozen water
. The breakthrough came last week when Phoenix's stereo camera caught the substance in the act of disappearing. Bathed in martian sunlight for four days, the white substance sublimated — i.e., it transformed from solid to gas without passing through the liquid state. This is how water behaves on Mars. Atmospheric pressure on the Red Planet is so low (1% that of Earth), it rarely allows H2O to exist in liquid form on the planet's surface; solid and gas are the only options. Some readers have asked, how do we know the white substance is not frozen CO2 (dry ice) instead of frozen water? Answer: Phoenix's landing site is too warm for dry ice. The average daily temperature is about -70 F while dry ice requires temperatures lower than about -109 F.
the article includes an animated gif showing the ice sublimating."