Originally published June 30, 2012
|image by Antonio Lasala García, Morata de Jalón, Zaragoza, Spain|
What did this crater, Hipparchus, look like one minute before the impact of the projectile that formed the Imbrium Basin? With a diameter of 138 km it probably looked much like the better preserved Neper (D = 137 km). It would be 4-5 km deep, with massive terraces and a large peak at the center of its floor. Neper has a lava covered floor because it is on the edge of a maria, Drygalski is about the same size (149 km) and far from mare lavas. Drygalski also has a broad flat (non-mare) floor, so that is probably what Hipparchus had too. Hipparchus is only 1.1 km deep so it has been filled in by 3-4 km of something, probably ejecta from Imbrium. Craters that formed on its pre-Imbrium floor were inundated by the ejecta and only the top-most ones are barely seen. Just as the floor was greatly modified so were the crater's walls. Hipparchus' rim stuck up into the hurricane of horizontally travelling ejecta and was gouged and lacerated. By the bad luck of being not too far from the Imbrium Basin Hipparchus was instantantaneously aged, becoming a battered ruin in a matter of minutes.
2012-06-26 19:04 to 19:06 UT - a daylight image. Newton 254 F29 + filter: r25 + camera: Basler acA640-100gm
Rükl plate 44
Yesterday's LPOD: Submerged Terrain
Tomorrow's LPOD: Another Half Crater
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