April 8, 2009
Rilles Almost All Around
image by Damian Peach
No, the vertical line crossing the top half of Arzachel's floor is not a mosaic seam boundary. It is the best view so far of a straight rille that was detected previously. With Damian's new image, there is a suggestion that the radial rille is tenuously crossed by a crater chain/rille extending from the bird's foot end of the Arzachel Rille. Opposite lighting supports this interpretation, but it is not certain if the connection is real. Damian's impressive image also confirms faint, apparently degraded rille segments cutting a rubbly area of the southern part of the floor. Thus, rilles have been imaged on three sides of Arzachel's floor; it will be interesting when modern orbiter images become available - or terrestrial imagers make the next quantum improvement - if rilles are found on the western side. If a crater floor moved up or down, I'd expect all parts to be fractured.
April 3, 2009; approx. 20:00 UTC. 14" telescope at 51°35"N, 00°45"W. Lunar altitude: 59°.
Rükl plate 55
Yesterday's LPOD: Big Backside Basin
Tomorrow's LPOD: The Best Image Map of the Moon