|Ice Found on Mercury|
NASA's Mercury-orbiting probe, MESSENGER, is providing evidence that water ice exists near the north pole of Mercury. Most of the ice is covered by a thin layer of material that blankets and protects the ice, but in a few areas where sunlight never reaches, some ice lies exposed on the surface.
Despite Mercury's proximity to the sun, the north and south polar regions remain cold because they never tilt toward the sun.
Evidence for ice deposits at both poles has been building since the early 1990s, when radar studies first spotted areas that looked very bright at radar wavelengths. These "radar-bright" regions suggested that some kind of reflective material lay on or very near the surface, and the locations turned out to be inside impact craters. More recently, extensive imaging by MESSENGER (short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging) made it possible to match up the radar-bright areas with permanently shadowed regions in craters near the north and south poles.
The ice seems to be the result of a geologically recent or ongoing process, perhaps delivered by comets and other small bodies from the outer solar system. Organic chemicals from those same bodies might make up the material that covers the ice in most places.
"These new findings let us discard the proposals that the radar might be picking up other reflective materials instead of ice," says Neumann. "Now we can focus on understanding the processes that are emplacing volatiles at Mercury’s poles."
NASA's Goddard Space Flight Center, Greenbelt, Md.