Nov. 28, 2012 -- Whether your favorite TV show was Dark Shadows or Northern Exposure, you'll get to enjoy a little of both in this new image from NASA's MESSENGER spacecraft!
Made up of a series of images acquired by MESSENGER's Mercury Dual Imaging System (MDIS) instrument, this projected view looks straight down on the north pole of our solar system's innermost planet. The images were taken over the course of 7 scientific imaging campaigns, and thus needed to be averaged together to create an evenly-lit final image.
Because Mercury's rotational axis isn't tilted like Earth's, the sun doesn't rise very high above the horizon at its poles over the course of its 88-day-long year. As such, the inner slopes of the deep polar craters seen above never receive direct sunlight -- and are thought to contain deposits of water ice.
Three times closer to the sun than Earth, Mercury's daytime surface temperature can soar to a scorching 425 ºC (800 ºF) but without much of an atmosphere to transmit or hold that heat temperatures on its night side can drop as low as -185 ºC (-300 ºF). Since these shadowy craters literally never see the light of day, any ice that's gathered there over the last 4.5 billion years will remain permanently frozen, harder than rock.
Originally posted by LeatherNLace
The images were taken over the course of 7 scientific imaging campaigns, and thus needed to be averaged together to create an evenly-lit final image.
Now the newest data from MESSENGER strongly indicate that water ice is the major constituent of Mercury's north polar deposits, that ice is exposed at the surface in the coldest of those deposits, but that the ice is buried beneath an unusually dark material across most of the deposits, areas where temperatures are a bit too warm for ice to be stable at the surface itself.
According to Paige, the dark material is likely a mix of complex organic compounds delivered to Mercury by the impacts of comets and volatile-rich asteroids, the same objects that likely delivered water to the innermost planet.The organic material may have been darkened further by exposure to the harsh radiation at Mercury's surface, even in permanently shadowed areas.