Martian Ice Confirmed, Exposed by Meteorite Impacts

Meteorites recently striking Mars have exposed deposits of frozen water not far below the Martian surface. Pictures of the impact sites taken by NASA's Mars Reconnaissance Orbiter show that frozen water may be available to explorers of the Red Planet at lower latitudes than previously thought."This ice is a relic of a more humid climate from perhaps just several thousand years ago," says Shane Byrne of the University of Arizona, Tucson.Byrne is a member of the team operating the orbiter's High Resolution Imaging Science Experiment, or HiRISE camera, which captured the unprecedented images. Byrne and 17 co-authors report the findings in the Sept. 25 edition of the journal Science.

[Images]: A fresh, 6-meter-wide, 1.33-meter-deep crater on Mars photographed on Oct. 18, 2008, and again on Jan. 14, 2009, by Mars Reconnaissance Orbiter's HiRISE camera. The bright material is ice, which fades from Oct. to Jan. because of sublimation and obscuration by settling dust.

"We now know we can use new impact sites as places to look for ice in the shallow subsurface," adds Megan Kennedy of Malin Space Science Systems in San Diego, a co-author of the paper and member of the team operating the orbiter's Context Camera.

So far, the camera team has found bright ice exposed at five Martian sites with new craters that range in depth from approximately half a meter to 2.5 meters (1.5 feet to 8 feet). The craters did not exist in earlier images of the same sites. Bright patches darkened in the weeks following initial observations, as freshly exposed ice vaporized into the thin Martian atmosphere.

The finds indicate water-ice occurs beneath Mars' surface halfway between the north pole and the equator, a lower latitude than expected in the dry Martian climate.

During a typical week, the spacecraft's Context Camera returns more than 200 images of Mars that cover a total area greater than California. The camera team examines each image, sometimes finding dark spots that fresh, small craters make in terrain covered with dust. Checking earlier photos of the same areas can confirm a feature is new. In this way, the team has found more than 100 fresh impact sites. ...

via Nasa.gov