This is interesting since it appears to show there is abundant water ice below the south polar cap within about a meter of the surface, the depth limit of the GRS instrument. It had already been argued that there is likely water ice below a CO2 cover at the south pole, though the thickness of this CO2 cover could be at the kilometer scale.
If the amount of water this close to the surface is at the several percent scale as suggested by these preliminary results then a water explanation might be possible for the "spider" features seen in the south polar regions. Dentritic features had been seen in these spiders. One proposed explanation of this is CO2 gas under pressure within the CO2 ice. However, a natural explanation would be flowing water under the ice.

The swirled "fingerprint" terrain seen at the south pole during summer might also be naturally explained as from convection due to water below the surface:

Icy Shapes on Mars Reveal Two Climates
http://www.space.com/scienceastronomy/solarsystem/mars_poles_000308.html

Bob Clark