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White patches on Mars are ice

After a decade of shouting, “Follow the water!” in its exploration of Mars, NASA can finally say that one of its spacecraft has reached out, touched ice and scooped it up.

Now, scientists will be able to tackle the main question they hope to answer: Did the ice ever melt and turn Mars into a habitable place?

In a photograph released Thursday night of a trench that the Phoenix Mars lander has dug into the Martian soil, some white patches that were seen earlier in the week have shrunk, and eight small chunks have disappeared. Until now, scientists were not sure if the white material was ice or some kind of salt.

When exposed to air, water ice can change into water vapor, a process known as sublimation. Salt, on the other hand, is not capable of such a vanishing act.

“It must be ice,” said Dr. Peter Smith of the University of Arizona, the mission's principal investigator. “The whole science team thinks this. I think we feel this is definite proof that these are little chunks of icy material.”

Water ice on the surface of Mars is not new. Scientists have known that the permanent cap at Mars' north pole is made of ice. In 2002, measurements by the Odyssey spacecraft found evidence for vastly larger quantities of ice not far beneath the surface.

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