[과학]Reuters; NASA extends Phoenix mission as snow falls on Mars (영어 발표)

NASA extends Phoenix mission as snow falls on Mars     By Maggie Fox, Health and Science Editor   WASHINGTON (Reuters) - NASA extended the mission of the busy Phoenix lander Monday, saying it will operate the lander until it dies in the cold and dark of the Martian winter.   It is already snowing there, above the equivalent of the Arctic circle on Mars, the researchers said.   The explorer found evidence that the dust on the surface of Mars resembles seawater in its chemical makeup, adding to evidence that liquid water that once may have supported life flowed on the planet's surface.   The Phoenix lander already has operated far longer than expected when it was dropped onto the Martian surface in May, and its controllers said they would squeeze every drop of life they could out of the solar-powered lander.   "We are literally trying to make hay as the sun shines," Barry Goldstein, Phoenix project manager at the Jet Propulsion Laboratory in Pasadena, California, told reporters.   Scheduled to last just 90 Martian days, known as sols, the lander has already operated for more than 120.   But soon the sun will dip below the horizon until next April. Already the lander is getting less power, after a summer of light-filled days that resemble the months of daylight enjoyed at the Earth's poles in the summer.   Mars weatherman Jim Whiteway of York University in Toronto, Canada, said the lander has seen snow, frost and clouds forming as the atmosphere cools, although the snow is vaporizing before reaching the ground.   "Nothing like this view has ever been seen on Mars," Whiteway said. "We'll be looking for signs that the snow may even reach the ground."   LET IT SNOW   Scientists had known it likely snowed on Mars but the lander got unique measurements showing it happening in real time.   The lander has already gathered more evidence of water on the surface of the now-dry planet. In July, the Phoenix team reported definitive proof that water exists on Mars after the lander scraped up ice, and it also found perchlorate -- a chemical compound sometimes used by plants and microbes.   It also sent back the first-ever image of a speck of red Martian dust taken through an atomic force microscope. The latest analysis shows evidence of a carbonate chemical, likely calcium carbonate -- best known as limestone, said William Boynton, who leads a team that operates the lander's Thermal and Evolved-Gas Analyzer at the University of Arizona.   And, said JPL's Michael Hecht, further analysis shows the Martian dust is about as alkaline as seawater, with a pH of 8.3. This provides more evidence that life could have existed on Mars.   Peter Smith, Phoenix principal investigator at the University of Arizona, said Mars wobbles more than Earth does as it spins, so sometimes the poles are pointed directly at the sun. They would be warmer at those times, perhaps warm enough to melt the ice that Phoenix has confirmed lies just below the red dust.   "If you were to sweep away this thin soil layer on what looks like this flat plain you would find it is more like a skating rink," Smith said.   "Is this a habitable zone on Mars? I think we are approaching this hypothesis," he added.   Smith said the scientists plan to turn on a microphone that was supposed to record the lander's descent in May but which failed to do so. "We are going to try and turn on this microphone and try to listen to Mars for the first time," he said.   (Editing by Will Dunham and Vicki Allen)