left image by Jim Phillips, and right from Clementine
Lunar domes have many forms, including the rough textured and relatively steep-sided Arago examples and the classical hemisphere with a pit at its summit. There are also other types including one variant I call a swell because it is often lower and wider than typical domes. Jim has captured a good example of a swell on the south shore of Mare Frigoris under the crater Archytas G. The swell is very sharply bounded on its eastern side but only a few ridges possibly define its western edge. Another, larger and less certain circular swell occurs to the west, hemmed in by mare ridges. The ridges in Frigoris are different from those in most maria - they aren’t clustered around its edges but seem to create roughly orthogonal patterns unrelated to anything obvious. The Clementine image shows nothing of the low structures that Jim’s view captures so well, but does reveal the well-known concentric structure within Archytas G. The association of the concentric crater with a swell provides general support to the idea that somehow concentric craters are related to volcanism.
June 23, 2007, 1:25- 1:30 UT. TMB 8″ F/9 @ F/45 + Atik B&W webcam + K3Tools, Registax & Photoshop.
Rükl plate 4
Yesterday's LPOD: An Ordinary Mare Transformed
Tomorrow's LPOD: Map of Mystery