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Mars Craft Detects Falling Snow

Smith said that in the remaining weeks, the scientists plan to turn on a microphone that was designed to record the lander's descent in May. It did not work then, but Smith said, "We are going to try to turn on this microphone and try to listen to Mars for the first time."

Phoenix was scheduled to operate for 90 Martian days, known as sols, but the lander's robotic arm has been digging up soil and ice for more than 120 sols and delivering it to chemistry labs inside the lander. Smith said many of the mission's primary goals have been accomplished, although difficulties transferring the scooped-up material into the lander have interfered with some experiments.

In particular, researchers are eager to know whether the isotopic makeup of the water in the air is the same as the water in the soil, but they have not been able to load the proper material to find out. They have searched in vain for organic (although not necessarily biological) material in the soil.

Scientists have theorized that snow falls on Mars, but they had never before seen it in real time. Future research on the data collected by Phoenix will try to determine where the snow came from -- whether it originated in the ice-covered polar regions or evaporated from the broader Martian surface, or even from the large collections of ice below the surface.

The Phoenix team was surprised in the summer by the presence of the chemical perchlorate in the Martian soil. Used in many industrial capacities and in rocketry, the potentially toxic chemical is also found in the driest deserts on Earth. Smith said its presence on Mars suggests again that there was once liquid groundwater and raises the possibility that life has existed in the planet's seemingly hostile environment.

Because perchlorate changes the freezing point of water dramatically, it could keep water in a liquid state at temperatures of 76 degrees below zero.

"This could form brines for microbes, which could then use the perchlorate as a chemical energy source," he said.

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