Deeper Martian Ice

Scientists using the radar on the Mars Reconnaisance Orbiter to probe the ice cap over the north pole of the planet have found the ice there to be thicker than expected. They've also found it to be layered-- dusty layers alternating with layers of pure ice. Like the icefields on Earth, the north polar cap on Mars maintains a history of the planet's climate changes.

Thicker ice caps means flowing water is deeper below the surface. When NASA's Phoenix probe lands in the polar regions later this month and digs into the surface, it will hit ice, not water.