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قطب شمال عطارد را بنگر !
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[تصویر:  13542124031.png]





Dark Shadows Freeze Mercury's North Pole
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.



ANALYSIS: Mercury Not Too Hot For Polar Water Ice?



On March 17, 2011,
NASA's MESSENGER became the first spacecraft ever to orbit the planet
Mercury, and to date has returned over 125,000 images of the first
planet from the sun... many revealing features and terrain that had
never been seen before. See more images and news from the MESSENGER mission here.



--by Jason Major



Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington




















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