by Matt Tarlach
South of Crisium a narrow peninsula reaches out into Fecunditatis, toward Webb. Last night with the terminator at 67d E a dark rille- like shadow could be seen tracing most of the length of the crest of this peninsula. This "rille" is shown in Rukl (Chart 38) and appears in Lunar Orbiter photo IV-184-H1: http://www.lpi.usra.edu/research/lunar_orbiter/images/aimg/iv_184_h1.j pg
I've seen many rilles that cross high terrain but this is the only one I can think of that traces along a high ridge in this manner....unless you count Schroeter's Valley which winds across the Aristarchus Plateau. I couldn't find any commentary on the Webb "rille" in my resources, which include Chuck's book and a few other amateur guidebooks. Can anyone shed light on its nature? I'm always hoping to spot evidence of lunar vulcanism and fantasized that the ridge could be a leveed lava channel (please excuse the amateur geology!). But the texture of the ridge looks more ejecta.
Moving on: northwest of Langrenus, the craters Bilharz, Atwood, and Naonobuare are arranged on Fecunditatis like the three corners of a square. Where the fourth corner should be I noted several bright spots and roughness in my 150mm scope under middling seeing. Checking the CLA and LA photos I found that the area is spattered with a few dozen small, often irregularly shaped craters. It looks a lot like the blast pattern from a shotgun! http://www.lpi.usra.edu/research/lunar_orbiter/images/aimg/iv_053_h3.j pg What happened here? Did perhaps a loose "rubble-pile" asteroid, or a comet, or a clump of basin ejecta disintegrate into small pieces just before impact?
Lastly, exploring the region of Valles Snellius and Rheita, several of the less obvious crater chains and valleys that run parallel to these named features were easy to see. There appear to be two overlapped systems, as all of the major furrows appear to be aligned in one of two directions. It looks like an interplanetary cat took two sharp-clawed swipes at the Moon! Each half of the "bent" Vallis Rheita lines up nicely with other furrows in the two systems.
In Chuck's book he ascribes all of these grooves, furrows, and crater chains to Nectaris. But I notice the features that are aligned tangentially to Nectaris appears to be, as best I can tell, radial to the center of Imbrium. Is it possible that Imbrium sculpture could extend so far across the Moon?
Clear and steady skies, everyone!
Posted on starrynights Oct 31, 2004 18:35:03 PT
Converted by report.pm 1.2 Jan 16, 2005 08:54:17 PT