February 17, 2005

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Keeping Up With The Smythiis



Image Credit: Mario Santiago

Keeping Up With The Smythiis

The equatorial eastern limb of the Moon is more interesting than much of the terrain immediately nearer the Earthside. The reason is twofold: (1) the area between Crisium and Fecunditatis and the limb is boring because it lacks any distinctive large fresh craters, and instead is a mishmash of older, look-alike craters flooded with and surrounded by mare material; and (2) the limb is home to two maria – Marginis and Smythii – that occupy two impact basins. Of the two, Smythii offers more vestiges of its basin structure – principally its well-defined, curved rim. When the sunset terminator is just east of Smythii you can observe the shadow cast by the rim and appreciate that the mare is substantially lower than the rim. In fact, Clementine altimeter readings show that the rim rises an amazing 6-8 km above the mare. The circular outline of the rim is clearly demonstrated in Mario’s rectified view (mouseover) of Smythii made using PlanetWarp. Also clear is the two different shades of mare lavas. Crater counts imply that the darker Smythii lavas may be among the youngest on the Moon, perhaps 1.5 b.y. old.

Chuck Wood

Technical Details:
13/02/2005 at 18:09/18:15 UT (in daylight!). 2 images mosaic made with Orion SkyView Pro Newtonian (8 inches f/5) + Ccd Atik 2HS + Barlow 2x + Qcfocus + Registax. Planet Warp v.1 used for warped image.

Related Links:
Rukl Plates 38 & 49

Yesterday's LPOD: A Newly Named Crater

Tomorrow's LPOD: Memory of a Crater

Author & Editor:
Charles A. Wood



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