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Planetary scientists looking for water ice on Mars have employed a number of tactics to great success in their search. The Phoenix lander dug it up; orbiting radar measurements have seen it under insulating blankets of debris. (Frozen water sublimates to vapor in Mars's climate and so is not stable when exposed at the surface.)

Now a team of researchers has let meteorite impacts do the digging for them—a paper in this week's Science presents observations of fresh impacts and what they turn up from below the surface.

Using instruments on NASA's Mars Reconnaissance Orbiter (MRO), a group led by Shane Byrne, a planetary scientist at the University of Arizona's Lunar and Planetary Laboratory, found five recent impact craters in the Martian mid-latitudes, near the boundary where subsurface ice is thought to be no longer tenable. All were relatively small, ranging in size from about four to 12 meters across.

In three cases, the craters were less than a year old, because imagery of the same regions just months prior had shown no such impact scar. But all five showed visual indications of ice, and at the crater with the largest presumed ice deposit, the icy composition was confirmed by the orbiter's spectrometer. (The suspected ice blankets around the other four craters, each occupying only a fraction of a spectrometer pixel, were too small to register in the instrument's readings.)

By checking on the craters over time, MRO saw the bright excavated material fading, consistent with sublimating ice. Modeling the sublimation process for one of the craters, the team concluded that the upturned ice was nearly pure, with a debris content of less than 1 percent. The others appear to be comparably clean also.

Byrne and his co-authors note that the monitoring of such relatively common craters and their ejected ice can give scientists a view of the Martian ice table's boundaries and depth, as well as helping to constrain how much water Mars had in its atmosphere in the past.

Photo of an eight-meter crater surrounded by what appears to be clean ice: NASA/JPL-Caltech/University of Arizona

6 Comments

1. 1. freeasthewind 04:32 PM 9/25/09

   To: Whom who are sick and tired to live on earth
   
   Dear prostective Mars settlers,
   
   As you have been convinced by NASA and nature that water on Mars is plentiful for you to use to live and to grow corn and raising chicken and goats and dog and cat over there!
   And for sure, I believe that sooner or later many but not all folks on earth will move to Mars to stay for awhile or live permanently there for claiming as citizens of Mars instead of the earth!
   
   So
   
   it is time to build a larger and safer Mars-buse or Mars-Shuttle spacecraft to move to Mars and start farming like people on Earth have done !

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2. 2. freeasthewind 04:35 PM 9/25/09

   WATER! WATER!
   
   IT IS TIME TO PACK UP AND MOVE TO MARS TO GROW CORN AND RAISING CHICKEN! AND GOATS AND COWS!
   MAYBE NASA CAN BUILD FASTER MARS-SHUTTLE BUSES TO ALLOW PEOPLE FROM EARTH TO GO TO THIS RED PLANET!
   WE WILL MAKE THIS RED PLANET TURN GREEN FULL WITH GRASS AND CORNS AND OAK TREES!
   \
   AND WHY NOT?
   
   SO,
   
   LET'S GO BOYS!
   
   SEE YOU THERE! SOONER IS BETTER!

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3. 3. mikehattan 09:42 AM 9/27/09

   Please leave all religious fanatics behind here on earth and let God sort 'em out!

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4. 4. aaanouel 09:40 AM 10/6/09

   To those who are sick and tired to live on earth...
   No matters where, you'd better learn to live, just live, and learn to enjoy our beautiful planet the way it is. To learn to appreciate your resemblances the way they are, to enjoy work and the work of dealing with others. If not, no different planet will be created and no happier place could exist in the whole universe.

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5. 5. Vaseghi 09:46 AM 11/29/09

   As like as small crumbs of a bright material called "Dodo-Goldilocks" buried under a thin layer of dirt, is not water ice but truly it is mineral mirabilite by thenardit. ( Thenardite, Na2SO4 samples will gradually absorb water and convert to the mineral mirabilite, Na2SO4,10H2O. Or vice versa)
   You can see similar matter on Earth's desert.
   http://rapidshare.com/files/285656551/Mars.jpg
   Ali Vaseghi
   MSc Prospector

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6. 6. joetommasi 03:55 PM 12/30/09

   How can we tell if the ice was there to begin with adn got dug out or it came down as a small comet and splattered all over the place?

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