DAYTIME temperatures on the planet Mercury can be as high as 425 ℃. So, one would think that it is an unlikely place to find ice. But the poles of this airless planet can be surprisingly frosty. Using images and elevation data from the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft, a team led by Michael Barker of NASA’s Goddard Space Flight Center inspected a permanently shadowed north polar crater named Prokofiev. This area was found to contain a radar-bright region that the scientists believe to be surface ice.
As shown in the images, Barker and collaborators modelled the crater’s elevation, illumination, maximum temperature, and depth below the surface at which water ice could be stable and were able to confirm that the crater has the right conditions to host surface ice. Further analysis suggested that the radar-bright region may be a layer of ice up to 26 metres thick. The ice apparently is not pure water though. Part of it is covered by a dark silicate or hydrocarbon material, the exact nature of which remains unknown.
The findings were reported in a recent issue of Planetary Science Journal.