High in the sky above Mars, it is snowing right now. Very gently snowing. The snow does not settle on the rubble-strewn land below - not these days, anyway - but instead vaporises into the thin atmosphere long before it reaches the ground. The first flakes of snow, on a planet that until fairly recently was believed to be waterless, were spotted just a few months ago. A Nasa lander near the planet's north pole was scanning the sky with a laser when it noticed the telltale signs of snowfall.
The probe, called Phoenix, announced the news in a radio signal that was picked up by an overhead orbiter and beamed back to Earth. Nothing like it had ever been seen before. The news of snow falling is just one piece of an extraordinary wealth of information that has recently been sent back from Mars by orbiters, landers and rovers. Together, they have mapped the surface in unprecedented detail, cracked open rocks, sniffed the atmosphere and dug down into the soil. What they have found points to an unimagined Martian history, one where life may have once gained a foothold and may even cling on still in the frigid soils of the permafrost.
Mars is a planet where scale is redefined. It is half the size of Earth, but home to what is probably the largest mountain in the solar system, the 16-mile-high Olympus Mons. Just beneath its equator is a truly grand canyon that also sets a solar system record. The Valles Marineris is as long as the US is wide, and in places reaches 10km deep. (Source: Sign Of The Times)
