Water Ice On Mars

cathector sends along a story from SpaceWeather.com on the discovery of water ice on Mars. "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.... 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 animated GIF showing the ice sublimating is pretty nice too.

Comments

average daily temperature

[Swampash]

Could we have this important information in units used by, I don't know, the rest of the world?

ice on Mars is nothing new

[speedtux]

Finding water was one of the key goals of the Phoenix mission.

That is a bizarre statement. Large quantities of ice have been observed in numerous ways already. Even the Viking lander observed water frost directly in the 1970's:

http://en.wikipedia.org/wiki/Viking_2

http://www.solarviews.com/cap/mars/frost.htm

That frost sublimated just like this ice did.

Here are other observations:

http://science.nasa.gov/headlines/y2002/28may_marsice.htm

Here you can see a frozen crater lake:

http://esamultimedia.esa.int/images/marsexpress/210-010705-1343-6-co-01-CraterIce_H.jpg

http://www.esa.int/SPECIALS/Mars_Express/SEMGKA808BE_0.html

Not only is that ice, it may actually be an outflow.

What makes the results from Phoenix exciting is that the actual experiments that Phoenix is supposed to perform depend on having landed on ice. But finding ice somewhere on Mars is not a surprise.

Re:Water sublimating

[PieSquared]

Pretty much anything can sublimate under the proper conditions. But when you say "a white solid that sublimates at -70 degrees F and martian surface pressure and is found in macroscopic quantities naturally" you narrow down the field quite a bit. In this case, to exactly one reasonable possibility.

Re:Wind?

[Free the Cowards]

Neither, because NASA only hires smart people.