Mars Water Mystery Surfaces

By Andrea Thompson Senior Writer posted: 05 September 2008 10:03 am ET

New data from Mars' surface is puzzling NASA scientists: A fork-like probe on the Phoenix Mars Lander has sensed changes in humidity in the Martian air, but finds the dirt below perplexingly dry.

The measurements, the latest of which were taken over the last few days, indicate that water vapor is settling on or in the Martian dirt then being released back into the air on a daily cycle. So mission scientists have expected to find water molecules sticking to the Martian surface.

"If you have water vapor in the air, every surface exposed to that air will have water molecules adhere to it that are somewhat mobile, even at temperatures well below freezing," said Aaron Zent of the NASA Ames Research Center in Moffett Field, Calif., and the lead scientist for Phoenix's thermal and electroconductivity probe, which is making the humidity measurements.

Phoenix's mission on the red planet, which began after a May 25 landing there, is all about the tantalizing search for Martian water. The lander has already confirmed the presence of a subsurface layer of water ice, first detected in 2002 by NASA's Mars Odyssey orbiter, which is still circling the planet.

More at www.space.com