Subsurface ice on Mars exposed by recent impacts.
19:22 30 March 2009 by Kelly Beatty, The Woodlands, SkyandTelescope.com
"Over the years spacecraft have glimpsed ever-finer features in the Martian landscape. These days, the HiRISE camera aboard NASA's Mars Reconnaissance Orbiter (MRO) can pick out objects only 0.3 metres in size; the High Resolution Stereo Camera on the European Space Agency's Mars Express is no slouch either, with a ground resolution of 2 metres.
"So HiRISE researchers were elated, but not particularly surprised, to discover some small, freshly gouged craters in images taken in 2008. Seen at five sites over a latitude range of 43° to 56° north, the excavations are typically 3 to 6 metres across and a third to two-thirds of a metre deep. One cluster must have appeared sometime between June and August, and a somewhat larger pit showed up between January and September.
"What did astound the team were splashes of white seen in and around a handful of these craterlets. Could it be water ice? Colleagues operating the spacecraft's CRISM instrument soon confirmed, for the one case large enough to yield a spectrum, that it was! Apparently fist-sized impactors had punched into a layer of ice hidden by a topping of dust about a third of a metre deep."
http://www.newscientist.com/article/dn16867-subsurface-ice-on-mars-exposed-by-recent-impacts.html

Here's the Lunar and Planetary Science Conference report referenced:

MODELING SUBLIMATION OF ICE EXPOSED BY RECENT IMPACTS IN THE MARTIAN MIDLATITUDES.
C. M. Dundas1, S. Byrne1, A. S. McEwen1 and the HiRISE Team. 1University of Arizona, Department of Planetary Sciences, Tucson, AZ, 85721 (e-mail: ****@lpl.arizona.edu).
http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2168.pdf

At about a foot deep, this ice may be shallow enough to reach the subzero temperatures for melting ice with salt or perchlorate mixed in at least during Martian summer.

Bob Clark