February 17, 2018
Originally published September 11, 2008
images by Jim Phillips and Pavel Presnyakov
By chance, two images came in today that show the same area under different lighting. Jim, who prowls the terminator for domes, sent the left image, and Pavel submitted a mosaic of the northern polar regions that included the same region. Can you identify it? The area is part of the non-descript central-western end of Mare Frigoris between Plato and J. Herschel. Under most illuminations the mare here is relatively featureless, but when the terminator is near, low ridges and swells become visible. I see about half a dozen broad, flat swells, which are probably places where gas trapped under slowly flowing lava lifted the surface and held it up until it cooled solid. This seems reasonable until it is realized that these swells are up to 10 km wide - that would have required a huge volume of gas to lift up a heavy lava roof. Although lunar lavas lacked any significant amounts of water, the most common volcanic volatile on Earth, vesicles (bubble holes) in lunar basalts show that other gases were common. Perhaps there are void spaces under some of these blisters that someday will be rustic hotels.
Left: Sept. 9, 2008. TEC 200 F/8 Flourite @ F/40. Right: August 23, 2008, 02:15 UT. TAL-250K + barlow 3x + Vac-135, b/w 1280x1024 + Baader IR-pass filter. 100 km from Kiev Ukraine.
Rükl plate 3
Yesterday's LPOD: A Bigger, Older Clavius?
Tomorrow's LPOD: Tycho & Tokyo