Fabulous Fab!
Explanation:
Have you ever looked carefully at Fabricius? I hadnt until I studied this great image. Usually Fabricius is seen as an obstruction hiding part of the floor of the large crater Janssen, but it is a fascinating crater in its own right. Fabricius (diameter 78 km) is mostly a Tycho-like complex crater, with terraced rim, flat floor and central peak. But the floor contains a horseshoe-like massive ridge. This is does not make Fabricius a floor-fractured crater - their concentric pattern is of rilles. I would guess that the floor arc of Fabricius formed by a terrace sliding down the crater walls. The ridge is completely free of the wall on the NW side, but is adjacent to the SE wall, like a normal terrace. On the southern portion of the floor a small crater occurs in the middle of a short rille, one of the few in a highlands crater. The rim of Fabricius has two abnormalities to notice. On the left (S), an angular scallop suggests that a large rim collapse started but didnt collapse entirely. At the bottom (W) of the crater a thin ridge extends from the rim onto the adjacent highland and then curves back. This looks like another place where a rim scallop subsided only slightly. Compare this image with the Lunar Orbiter IV image - they have essentially the same resolution!
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Chuck Wood
Technical Details:
April 15, 2005. 18" dob + Atik webcam + 5X's barlow + Baader IR passband filter.
Related Links:
Lunar Orbiter IV View
Rukl Plate 68
