WASHINGTON - After years of proposing, theorizing, and deducing that there is water on Mars - at least in the form of ice - NASA scientists said 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 a 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 Mars, a key issue for scientists because, on Earth, liquid water is a key 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. In 2002, observations by the Odyssey 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 - what looked like ice underneath its landing site.
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.
"The fact that it melted at zero degrees Celsius leaves very little doubt that it is standard water ice," Boynton said. He said sensors also tested the chemical makeup of the vapor and found the familiar combination of two hydrogen atoms and one oxygen atom.
In a separate development yesterday, NASA said it has found liquid on Saturn's largest moon, Titan, making it the only body in the solar system other than Earth known to have fluid on its surface. Scientists identified the presence of liquid ethane, which is a component of crude oil.
The Saturn discovery was made using data from an instrument on board the Cassini spacecraft, which traveled more than 2.2 billion miles before entering orbit around Saturn in 2004, according to NASA's Jet Propulsion Laboratory, which manages the Cassini mission.
Phoenix is on a three-month mission to determine whether Mars can support life. It is conducting experiments to learn whether the ice ever melted in the Red Planet's history. It is also searching for the elusive organic-based compounds essential for simple life forms to emerge.
NASA announced yesterday that the Phoenix mission, originally planned to finish in late August, would be extended through the end of September. That extension will cost about $2 million, a NASA official said.
Scientists at the Jet Propulsion Laboratory cheered Wednesday when they received confirmation that the Martian soil contained ice.
"There were champagne corks popping in the downlink room," Boynton said.
The confirmation of ice on Mars was accidental. After two failed attempts to deliver ice-rich soil to one of Phoenix's eight lab ovens, researchers decided to collect pure soil instead. Surprisingly, the sample was mixed with a little bit of ice, said Boynton.
Researchers were able to prove the soil had ice in it because it melted in the oven at 32 degrees and released water molecules.