Mars' north and south poles are loaded with frozen water trapped under a crust of dry ice -- frozen carbon dioxide -- but this is not necessarily good news for any earthly visitor looking for a drink, scientists reported in Friday's issue of the journal Science.
That is because there is no liquid water in evidence.
Liquid water has been a quest of Mars astronomers for longer than a century. Apparent indications of surface water, including features that look like channels and river valleys, suggest the Red Planet might once have been warm and wet enough to sustain liquid water, allowing for the possibility of Earth-type life.
But new thermal images made by NASA's Mars Global Surveyor and Mars Odyssey probes show that although there may be a lot of water ice at both poles, there is nowhere near enough carbon dioxide there to ever warm the planet up enough to make the water drinkable.
The water ice would never melt on its own, being dozens of degrees below freezing.
Andrew Ingersoll, a Caltech professor and co-author of the Science article, said this scenario doesn't support "terraforming," a visionary approach to heating up Mars enough to unlock its frozen water.