Phoenix spacecraft which landed on Mars' northern plains in May
of last year carries a number of instruments to study the geochemistry
of the Martian 'Arctic'. It's 'lidar' instrument sends a laser pulse
of green light into the sky 100 times a second to continually collect
data about the Martian climate.
of last year, the Phoenix saw large water ice-crystals, or snow,
falling through the air. But unlike the artist's impression above,
the 'lidar' instrument did not follow the snow to the ground, which
suggests that it is vapourising before it reaches the ground. "This
is a very important factor in the hydrological cycle on Mars with
the exchange of water between the surface and the atmosphere."
said Jim Whiteway, of York University, Toronto, lead scientist for
the Canadian-supplied Meteorological Station on Phoenix. "Over
the first two months of the mission, the humidity of the atmosphere
was increasing as water [ice] sublimated from the ground and the
polar ice cap; and over the second half of the mission we've started
to see frost, ground fog and clouds. And this is now occurring every
night," explained Dr Whiteway.