A Canadian university’s laser aboard a NASA Mars lander has detected snow falling from Martian clouds about four kilometres above the landing site, and vaporizing before reaching the ground. “Nothing like this has ever been seen on Mars,” said Jim Whiteway, of York University in Toronto, the lead scientist for the Canadian weather station on the Mars Phoenix lander. “We’ll be looking for signs that the snow may even reach the ground.” Mars Phoenix landed in May at the edge of the Martian Arctic to investigate the soil, and especially to dig for water, in the form of ice. Ice appears and disappears near the Martian North Pole as the seasons change. But how the moisture moves around is unclear, especially as Mars has very little atmosphere — less than one per cent of what Earth has. Canada’s share of Phoenix includes lidar, a cousin of radar that uses lasers to scan the sky. Until now, it had found clouds, fog and blowing sand. Now, as Martian winter approaches, “it’s condensing in the atmosphere … and we’ve started to see frost, ground fog and clouds.” Photos from the little robot show fluffy clouds drifting across the horizon each morning. And lidar’s beam shows that inside those clouds, cascades of the heaviest ice crystals are falling inside the cloud. “So that is snow, falling from the clouds, and we’re going to be watching very closely over the next month for evidence that the snow is actually landing on the surface.” The next month may be all the team gets. Phoenix runs on solar power, and the sun will soon set for about three months, leaving the robot to freeze in the dark. It probably won’t survive. Nevertheless, the chief scientist for Mars Phoenix, Peter Smith of the University of Arizona, is happy. “The atmosphere is a transport mechanism for water-ice and vapour,” he said Monday.