Topic: Martian polar water or "water water everywhere"

[Nemesis]

Link to 1st article

Deep probe

Plaut and his colleagues probed the deposits with radar echo sounding, typically used on Earth to study the interiors of glaciers. The instrument, called the Mars Advanced Radar for Subsurface and Ionospheric Sounding, or MARSIS, beams radio waves which penetrate the planet’s surface and bounce off features having different electrical properties.

The reflected beams revealed that 90 percent or more of the frozen polar material is pure water ice, sprinkled with dust particles. The scientists calculated that the water would form a 36-foot-deep ocean of sorts if spread over the Martian globe.

Link to 2nd article

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 structure of Mars. "We didn't really know where the bottom of the deposit was," Plaut said. "We can see now 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."