David A. Fahrenthold
Washington Post 
Friday, Aug 1, 2008
After years of proposing, theorizing and deducing that there is water on Mars — at least in the form of ice — NASA scientists said yesterday they have finally confirmed it, after the Phoenix lander detected traces of water vapor wafting off a scoop of Martian dirt, researchers said yesterday.
“It’s something we’ve been waiting quite a while for,” said William Boynton of the University of Arizona, describing how an tiny “oven” on the lander heated the dirt until ice mixed with it evaporated. “We’ve now finally touched it and tasted it.”
Earlier Mars expeditions had indicated that at least in the past, water existed on the planet — a key issue for scientists, since on Earth, liquid water is a prerequisite for life. In the 1970s, photos seemed to show channels on the Red Planet’s surface, a possible indication that water had flowed there before the atmosphere cooled.
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In 2002, observations by an orbiting probe found evidence of vast amounts of water locked up in ice below the surface. Then, after the Phoenix Mars Lander touched down May 25, researchers said it had provided solid evidence of water.
But that was a deduction: The lander’s camera showed a group of small chunks, and then it didn’t. Researchers concluded that it was ice that had evaporated.
Yesterday, they said they had proof. The probe, which includes implements for scooping and gouging the Martian surface, had cooked a dirt sample in a special oven, and the scientists noted that a bit of the sample evaporated around the usual freezing point of water.