May 29, 2020

AstroEvent: Exploring Clavius.

This week, as the Moon moves past 1st Quarter on the 23rd toward Full on the 30th is a good time to explore the lunar environs. Specifically, I’d like to turn your attention towards Clavius crater, a prominent feature in the southern lunar highlands. One of the largest impact craters on the Moon at 152.2 miles across, it’s large enough to actually see the lunar curvature in its structure, and houses many smaller craters within its walls. It is visible starting at 9-10 days after New Moon, and presents a slightly different face each lunation. In fact, Clavius is one of the few craters that may be discerned by keen eyed viewers with the naked eye. In a small telescope, the relatively ancient structure of Clavius contrasts well with the nearby splashiness of young Tycho. Are these ancient, broad floored craters the result of impacts, or do they suggest early volcanic activity? Most of the rocks returned by Apollo astronauts were igneous and basaltic by nature, suggesting the young Moon once had a molten crust.

Clavius takes its name from German mathematician Christopher Clavius (1537-1612). Its lunar coordinates are 58.8° south, 14.1° west. To date, no landings, manned or unmanned have occurred in the region.  Of note among the numerous craters that litter Clavius is Rutherfurd, the 29.8 mile crater on the southern rim.

And of course, Clavius crater found has its way into science fiction lore; remember “Clavius Base” in the epic film/novel 2001: A Space Odyssey?

The astro-term for this week is Nectarian Period. This is the ancient period of time 3.92 to 3.85 billion years ago that the Nectaris Basin and much of the lunar highlands were to believed to have formed. This is a loosely interpreted and informal construct in lunar geologic time prior to the Imbrian, and sometimes used as a subdivision of the Hadean Eon.

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