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NASA has confirmed that chunks of soil that vaporized on Mars last month after NASA's Phoenix Mars Lander dug them up really were water ice.
The space agency announced yesterday that Phoenix detected water vapor in a soil sample fed Wednesday to its gas-analyzing instrument.
NASA researchers said readings from the Thermal and Evolved-Gas Analyzer (TEGA) indicated that ice in the soil melted at 32 degrees Fahrenheit (0 degree Celsius).
The result confirms 2002 observations by the Mars Odyssey orbiter, which detected ice in the form of subsurface hydrogen atoms at the planet's poles.
"We've seen evidence for this water ice before in observations by the Mars Odyssey orbiter and in disappearing chunks observed by Phoenix last month, but this is the first time Martian water has been touched and tasted," said TEGA lead scientist William Boynton of the University of Arizona's Lunar and Planetary Laboratory in a statement.
Collecting the soil sample from a two-inch- (five-centimeter-) deep trench dubbed "Snow White" took some doing. Phoenix dug a series of holes into the hard trench bottom with its drill-like rasp and twice scooped up dirt with its robotic arm for delivery to TEGA.
But both times, when the scoop was upside down, the icy soil clung fast and the samples were discarded.
Phoenix collected more scrapings on Wednesday, which NASA expected to be dry and therefore easier to handle, because most of it had been exposed to the air for two days, causing the ice to evaporate. But some ice remained.
In light of the success, NASA spokesperson Dwayne Brown says the agency extended the $420-million, 90-day mission by five weeks to September 30, at an additional cost of $2 million.
The mission length was chosen based on how much energy that Phoenix could collect from the relatively weak sunlight at various far northern locations on Mars.
The planet's northern hemisphere summer solstice occurred in mid-July, so the amount of sunlight declines each day, but NASA said there is enough for an added five weeks.
NASA spokesman Guy Webster of the Jet Propulsion Laboratory in Pasadena said the Phoenix team expects to complete all the experiments it had planned for the first 90 days within that period.
That includes tests to see whether Martian water thaws or has thawed and to inspect it for raw materials of life such as carbon-based molecules.
Webster said the extra five weeks will be used to study seasonal changes and to dig in additional locations around the craft.
The confirmation of water came a day after NASA announced that a shiny patch beneath Phoenix dubbed "Snow Queen" had shown changes in appearance, including the emergence of short cracks, which may represent slowly sublimating ice.