Fire and Water; June 2012; Scientific American Magazine; by John Matson; 1 Page(s)

Mercury is a world of extremes. Daytime temperature on the planet closest to the sun can soar as high as 400 degrees Celsius near the equator—hot enough to melt lead. When day turns to night, the planet’s surface temperature plunges to below –150 degrees C.

But some places on Mercury are slightly more stable.Inside polar craters on the dim­inutive planet are regions that never see the light of day, shaded as they are by the cra­­ters’ rims. The temperature there remains cold throughout the Mercury day. Now new data from NASA’s MESSENGER satellite, which were presented in March at the annual Lunar and Planetary Science Conference, corroborate a long-held hypothesis that Mercury has squirreled away pockets of water ice in those shadowy craters, despite the sun’s proximity.