Signs of snow on Mars

Phoenix Mars Lander captured its first signs of snowflakes falling from clouds high above the Red Planet.

This newest water sighting comes as the US space agency agrees to keep the rover running for as long as the frigid Martian winter will let it. (The three-month operation is now in its fifth month.)

The discovery, detected by one of the lander’s laser instruments, confirms NASA’s hunch that snow is possible on Mars.

“Nothing like this view has ever been seen,” says Jim Whiteway, lead scientist for the craft’s meteorological tools. In this case, the powder vaporized before it could hit the ground, but Mr. Whiteway says accumulation isn’t out of the question. They just have to find it to prove it.

Phoenix’s mission to Mars has uncovered several forms of proof that there’s frozen water on the now-arid planet. In July, it beamed home information on ice patches dwelling beneath the surface. This week, NASA also unveiled hints of calcium carbonate, the main ingredient in chalk and something that (at least on Earth) only forms with water. Scientists have detected carbonates elsewhere on Mars, but past sightings were all in places where there’s evidence that liquid water once flowed. The rover, on the other hand, landed in an “open plain” that's a good distance from any previous signs of running water.

The question now is whether any of this frozen water ever thaws – a potential clue in the hunt of life.