Scientists working with the Mars Lander mission believe the robotic arm on the lander has found ice crystals in the Martian soil. Crumbly bits of bright material like shown in the picture below have been unearthed, (or is the term here unmars-ed?),  but later disappeared after exposure to the sunlight.

The thinking is that it must be ice, for if it was a substance like salt, it would still be present. As ice, frozen water that is, it would have vaporized shortly after being uncovered by the robotic arm.

More digging by the robotic arm and further testing should help confirm this hypothesis.

Mars Lander 06.19.08

My guess is that it is ice. There is still a ways to go to determine how much is present and if any pools of water lie below the surface. It’s an interesting development. More data should be available later.