June 8, 2021

Skimming the Limb

Originally published October 20, 2011
image by Alexander Zaitsev, Lipetsk, Russia

This is the sort of scene I love to see in the eyepiece. A panoramic view, full of details, and full of geologic history, if I can untangle it. Looking westward across Orientale provides a basin view that complements the overhead perspective we get of Imbrium and most other basins. Here we look across multiple basin rings, seeing that they are mountain rims that stick up above the surrounding terrains. The largest and most impressive ring, but hard to see here, is the Cordillera Mountains that are most visible where slivers of maria lavas are immediately behind the mountains. Behind the mountains because they are giant faults, where the ground was ruptured as the basin interior subsided into the space evacuate by ejected rocks. The lavas rose up these mountain rim faults. You observe the same relationship of basin ring mountain faults being conduits to the longer sliver of Lacus Veris, just behind the mountains. The bright Rook Mountains closer to the limb are made of anorthosite rocks, part of the Moon's early slag crust and normally deep in the Moon but brought to the surface by the rebound of the impacted and compressed crust. Finally, right on the horizon is Mare Orientale, the small puddle of lavas that reached made it to the surface. Orientale is far from the KREEP-rich terrains centered under Imbrium, and there simply wasn't much mantle melting here or in most of the farside to produce voluminous maria. A lot of geologic understanding from one lovely mosaic.
Chuck Wood

Technical Details
2011/10/16, 22:22:52 UT. Telescope SW 305/1500 + camera DMK31 (b/w 30fps) with the red filter and barlow 3X.

Related Links
Rükl plate 50

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Yesterday's LPOD: Little Yellow Lines

Tomorrow's LPOD: Unsubtle Hues

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