May 20, 2009

Another Leak

Clementine image (above) and Lunar Orbiter 2-034M

Lunar volcanism, mostly mare lavas and some pyroclastics, occurs largely within and near impact basins. There are " rel="nofollow almost no examples of isolated volcanics in the nearside highlands. But on the farside the story is different. Most of the lavas there are indeed within a basin, the South Pole-Aitken Basin, but there are also about a dozen isolated leaks of volcanic material. Here is another one, centered at 166°E and 1.8°S. This cluster of dark material is scattered around small craters just north and east of 50 km wide Dewar. These look like normal impact craters, so presumably the dark material is buried basaltic lavas (or igneous intrusions - magma that hasn't erupted) that have been excavated by the impacts. The question is why are these volcanic rocks near enough the surface to be brought up by small crater impacts, but have not erupted on their own?

" rel="nofollow Chuck Wood

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Bussey & Spudis plate 85

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