New measurements of Mars' south polar region using the Mars Express Orbiter's powerful radar indicate extensive frozen water.  Estimates have now been upgraded, and it is thought the polar region contains enough frozen water to cover the whole planet in a liquid layer approximately 11 meters (36 feet) deep. A joint NASA-Italian Space Agency instrument on the European Space Agency's Mars Express spacecraft provided these data.  The new estimate comes from mapping the thickness of the ice, and the radar instrument has made more than 300 virtual slices through layered deposits covering the pole to map the ice.  The radar sees through icy layers to the lower boundary, which is as deep as 3.7 kilometers (2.3 miles) below the surface.

Scientists believe the south polar layered deposits of Mars, which cover an area bigger than Texas , contain significantly more water than has been estimated before.  The findings are published in the March 15 online edition of the journal Science.  The instrument, named the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), also is mapping the thickness of similar layered deposits at the north pole of Mars.

The polar layered deposits extend beyond and beneath a polar cap of bright-white frozen carbon dioxide and water at Mars' south pole.  Dust darkens many of the layers.  However, the strength of the echo that the radar receives from the rocky surface underneath the layered deposits suggests the composition of the layered deposits is at least 90 percent frozen water.  One area with an especially bright reflection from the base of the deposits puzzles researchers.  It resembles what a thin layer of liquid water might look like to the radar instrument, but the conditions are so cold that the presence of melted water is deemed highly unlikely.  Detecting the shape of the ground surface beneath the ice deposits provides information about even deeper structures of Mars.  Now it is possible to see that the crust has not been depressed by the weight of the ice as it would be on the Earth.  The crust and upper mantle of Mars are stiffer than the Earth's, probably because the interior of Mars is so much colder.