April 27, 2018

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Close-Up of a Rille

Originally published December 19, 2008 LPOD-Dec19-08.jpg
both images from A. M. Abdrakhimov and V. P. Shashkina, Vernadsky Institute, Russia

Hadley Rille is the only rille visited during the Apollo program of lunar exploration, but I have belatedly become aware of a close visit to another lunar linear depression 35 years ago. Although the Soviets did not send humans on the Moon they did land lunar rovers there twice. The Lunokhods were ungainly looking contraptions that worked quite well, exploring Mare Imbrium and as shown here, Le Monnier crater. Luna 21 landed along the southern part of Le Monnier's floor on January 15, 1973. In less than two hours Lunokhod 2 was driven (by controllers on Earth) off the landing vehicle and began a four month, 37 km exploration. Near the end of the mission the rover approached a linear trough from the west and then drove around its southern end and north along its eastern edge - this is indicated by the orange trail on the photomap. The trough, called Fossa Recta or Straight Trough by the Soviets was photographed in detail with the Apollo 15 panoramic camera (and also by Wes Higgins), revealing it to be made up of narrow rille-like depressions and aligned circular pits. This appears to be a lava tube, collapsed where the trough segments and pits are, and uncollapsed in the areas in between. The boulders along the edges have been interpreted as rare outcrops of lava flows. Finally, the names on the map do not appear in the Moon-Wiki lists of landing site names or unofficial names - we have some catching up to do!
Chuck Wood
I thank Phil Horzempa for alerting me to this paper and images.

Technical Details
Excellent interview with Sasha Basilevsky, one of the Lunokhod drivers. These and more images and information about the Lunokhod 2 mission are
included, of course, in Phil Stooke's monumental International Atlas of Lunar Exploration.

Related Links
Rükl plate 25
The 48th Vernadsky/Brown Microsymposium on Comparative Planetology (October 20-22, 2008, Moscow Russia).

Strange Fact
In 1993, the Lunokhod 2 and Luna 21 were sold at auction for $68,500 to Richard Garriott. Various people have bought land on the Moon, but is this
the only piece of anything on the Moon that is officially owned? See comment.

Yesterday's LPOD: M-Cubed

Tomorrow's LPOD: Stripped of Context


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