Phoenix Mars Lander spots snow on Mars

The US robot used its lidar instrument to probe the structure of clouds and saw large water ice-crystals falling through the Martian "air".

The instrument, which works by scattering pulses of laser light off particles in the sky, did not follow the snow to the ground.

The data suggests the snow vaporised before it reached the surface - but Phoenix is monitoring the situation.

"We're going to be watching very closely over the next month for evidence that the snow is actually landing on the surface," said Jim Whiteway, of York University, Toronto, lead scientist for the Canadian-supplied Meteorological Station on Phoenix.

"This is a very important factor in the hydrological cycle on Mars with the exchange of water between the surface and the atmosphere."