While the Mars Reconnaissance Orbiter has been circling the planet, the Phoenix spacecraft's Mars Lander has been sitting on the northern pole of the planet for several months, testing Martian soil samples for any elements - including water and ice - that could support life. A robotic arm on the Lander has dug up pieces of ice and the orbiter has sent back pictures of what looks like old fractures in the planet's surface and trails of waterways.

Scientists Monday added to that mounting list of scientific Martian discoveries with evidence of falling snow. "Nothing like this view has ever been seen on Mars," said Jim Whiteway, lead scientist for the Canadian-supplied Meteorological Station on Phoenix. "We'll be looking for signs that the snow may even reach the ground."

In a press conference Monday afternoon, NASA officials said that a laser instrument on the Lander has been taking readings of the Mars atmosphere, and recently detected snow falling from clouds about 2.5 miles above the planet's surface. The snow apparently is evaporating before reaching the ground.

NASA Monday also noted that recent soils experiments onboard the Lander found the presence of calcium carbonate, a main ingredient in chalk, and clay. Both are formed with liquid water. Evidence of calcium carbonate comes from two different machines onboard the Lander - the wet chemistry set and the analysis ovens.

"We are still collecting data and have lots of analysis ahead, but we are making good progress on the big questions we set out for ourselves," said Phoenix Principal Investigator Peter Smith of the University of Arizona.

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