November 29, 2012

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Bumps in the Night

image by Raf Lena, Rome, Italy

The Moon has tens of thousands of observable craters, hundreds of rilles, domes and mare ridges, and a handful of unique features. Many of the oddities are concentrated in Oceanus Procellarum, including Rümker, the Aristarchus Plateau, Schröter's Valley, and the Marius Hills. Across the Moon most familar small volcanic cones are standard domes like those near Kies, Hortensius and Cauchy. These were constructed by eruptions of lava flows from a central vent. Because the lavas were fluid they didn't build steep hills - normal domes have slopes of only a few degrees. But something makes the steeper-sided cones in the Marius Hills. If you look closely at Raf's image you may notice that the cones are quite irregular in shape. For some, the bottom has a gentle slope and the top is steeper. Others have an associated hilly flow. These observations suggest that the Marius Hills had different origins than the generic dome. There is spectroscopic evidence for ash at many of the cones so it is likely that explosive eruptions may have built lunar equivalents to terrestrial cinder cones. The hilly material surrounding some of the cones is probably viscous lava flows. The gentle slopes at the base of other hills may be due to normal dome lavas that are more fluid. So there are two unique features of the Marius Hills - there is a great concentration of volcanoes, and they have more pyroclastics than volcanoes elsewhere on the Moon. Asking why to both of these questions is reasonable, answering is hard.

Chuck Wood

Technical Details
Nov. 25, 2012, 23:28 UT. Mak-Cass 18 cm + Lumenera LU 075M.

Related Links
Rükl plate 29
21st Century Atlas chart 27.

Yesterday's LPOD: Don't Fall In

Tomorrow's LPOD: Golden


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