Visiting the Sun's anvil

Until last week, space scientists had been waiting to get a close-up glimpse of the planet Mercury for 33 years. But thanks to NASAs new Mercury MESSENGER spacecraft, theyre finally getting a stream of new images that show the sun scorched, cratered surface of the First Planet. The name MESSENGERrecalling Mercurius, the messenger god of ancient Rome and the planets namesakeis short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging. Over a half dozen delicate instruments began their work during the probes first flyby of Mercury Jan. 14. Last Monday, NASA technicians began pouring through more than 1,200 new images that were radioed back by MESSENGER as it passed the Sun-pounded planet. And what a tortured place is tiny Mercury! The planet, which looks superficially like our Moon, sports thousands of impact and volcanic craters, great cliffs, mountain ranges and shadowy valleys. Mercury is the solar system innermost planet. It takes 88 days to orbit our Sun. It has no known natural satellites and no atmosphere. As planets go, Mercury is extremely dense. The planet has a large molten iron core which generates a magnetic field about 1% that of Earths. The surface temperatures on Mercury make a big swing from a frigid -183.1 C/-297.7 F at night (and in the shadows) to a near molten + 427 C/+800 F during the day. The bottoms of craters near the north and south poles are the coldestso cold in fact, that some astronomers believe vast water-ice deposits are buried there. NASAs MESSENGER is about the size of a 2008 Chevy Colorado truck. Its visit to Mercury last week was actually the first of three so-called flybys of the planet. It will finally settle in to a long-term orbit of the planet on March 18, 2011. Then it will begin regular monitoring of Mercurys battered face. Last week, MESSENGER passed 200 kilometers (124 miles) above Mercury and snapped the first pictures of a side of the planet never before seen by spacecraft eyes. This imageavailable on the Internet at Nasa.gov and elsewhereshows Mercurys mysterious south pole. The image shows the stark transition line from the sunlit, dayside, of Mercury to the dark, nightside of the planeta transition line known as the terminator. At the terminator, a future astronaut could almost physically straddle the -297.7 F/+800 F dividing line with one booted foot set in frigid darkness and the other boot set on the Suns fiery anvil. According to a joint NASA-Johns Hopkins University news release, near Mercurys terminator line, the Sun shines at a low angle causing the rims of craters and other elevated surface features to cast incredibly long shadows. Last weeks amazing images will be used by space scientists to create an entirely new, high-definition global map of Mercury. The images will also help geologists figure out how internal and external processes shaped the barren surface of dessicated Mercury. WHATS IN THE SKY: Theres not much to look at in our northern sky on evenings this month. On a clear night, its rather disconcerting to see such an apparent lack of stars in the sky. No matter, look for the lonely constellation Camelopardalis in the north around 8 or 9 p.m.

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