April 4, 2012
image by Michael Wirths, Baja California
This is a piece of the magnificent Altai Mountains ring of the Nectaris Basin. The big complex crater near bottom center is Piccolomini and the southwest corner of Fracastorius is at top right. A broken line of mountains defines an inner basin ring about half way between the two big craters. With this lighting it looks like the mountain fragments are linear and aligned radial to the basin center. Inside this ring the topo is lower and partially filled with smooth material that may be old maria that has lost its dark coloration due to a long period of dusting by bright ejecta from subsequent craters. There seem to be more craters and remnants of craters in the moat between the two rings than in the smoother material adjacent to Fracastorius. That is consistent with the smooth stuff being younger. The roughness of the terrain outside the scarp is suggestive of basin ejecta, which is what would be expected outside the major basin ring. But similar material occurs in the moat north west of Picco. If it also is basin ejecta then the Altai Scarp can’t be the main basin rim. That is the situation at Orientale where the massive Cordillera Scarp surely seems to be the basin rim. But material around the Rook Mountains, inside the Cordilleras, is also interpreted as basin ejecta forcing geologists to say the Cordilleras are not the main rim. I have a hard time accepting that interpretation for both Nectaris and Orientale, wondering if the ejecta stayed in flight long enough for the basin rings to form with some ejecta falling inside the main rim. Or perhaps the stuff is not ejecta but something else.
Note: This was written on Tuesday night during a power failure with the light of the laptop screen being the only illumination in the house. I don’t know when it will get posted.
2012-03-27 Starmaster 18" (Zambuto primary) Lumenera Infinity 2-2 mono, True Tech R/IR filter stack of 118 frames (out of 1100) Processed with Avistack version 2 and PS CS.
Rükl plate 57
Yesterday's LPOD: Latitudinal Band Pan
Tomorrow's LPOD: What a Difference a Day Makes, 24 Little Hours