April 27, 2007

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Necho's Peculiar Rays

Apollo 11-44-6657 image (left) from Apollo Archive and Clementine color ratio image (right) from Map-A-Planet. Make your browser window wide enough so that the images are side by side.

The farside is frustratingly hard to study. There aren’t good maps or images (Clementine’s have phase variations and Lunar Orbiter and Apollo are piece-meal with various resolutions and look angles). But there are many bizarre features. Necho is a very fresh 30 km diameter crater on the SE quadrant of the farside. Necho’s rays are very asymetrical, extending five or more times further to the north-northwest than in any other direction. This suggests an oblique impact, with the projectile coming from the south-southeast, but there is not a zone of avoidance in that direction. The Clementine color ratio image also suggests that King crater interupts - and hence is younger than - the Necho rays. This is peculiar because although King is also young, it doesn’t have a significant ray system. I’ve always thought that Necho was the younger of these two craters, but now I’m not sure.

Chuck Wood

Related Links:
Geology of the lunar farside crater Necho, Gifford, A. W.; Maxwell, T. A.; El-Baz, F., Moon and the Planets, vol. 21, Aug. 1979, p. 25-42.

Yesterday's LPOD: Lunar Slide

Tomorrow's LPOD: Getting Cozy with Posi


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