QUOTE(dcman @ Aug 1 2007, 02:00 PM)

Okay this just in. I asked a former engineer for NASA and this is what he said:
"Ok. There are several factors contributing to the object. Let me explain. First, the image is lighted from the top at an angle of about 20 degrees from the left of center. Note that if you allow your mind to think that the light is from the bottom of the image, all the craters appear to be bubbles rather than depressions. Second, the cratering in this region is significant in that there are craters on craters with some small craters on crater walls of older ones. Third, the complete set of images, containing your object, start at 1033 and go to 1041(just up date the last digit of the url),(If you save these images to a folder and use M/S photoeditor like I did you can make a very short movie of the fly-by). In image 1041 your object is at the very bottom of the image, near the edge of the frame. This frame places the camera almost directly over the object. Fourth the center of interest in this series of images, for NASA, is the landing site, thus your object is imaged from almost overhead and not centered. Fifth, the moon is much smaller that the earth and its surface sphericity is severe. Therefore, your point of interest is, in effect, rotating toward the camera as the lander moves toward the landing site. Sixth, most of these images from this time are taken on film of an scene that provides extreme contrast. Thus, the eye is overloaded with information causing some objects to appear round when they are flat or only slightly curved. (Just like paintings that look 3-dimensional; lighting is very important for interpretation)
Taking all this into account, I think your object is a ledge on the outer and sun-ward side of a rim of a crater that has been penetrated by several other impacts. The curvature of the crater rim and lighting gives the impression of pointed ends and rounding. This is way too much fun. I usually get distracted by all the other stuff in the series of images."
There you go...take or leave it.
First of all, the picture you posted was already linked.
It's one of the Apollo 15 metric mapping camera images. This one appears to be a crop of AS15-M-1037, taken from an altitude of ~ 73 SM, 74 degree field of view, showing, in the full frame, ~ 200 SM miles from end to end. The sun's angle was 29 degrees at this point on REV 33, it's direction from the top left side of the frame, as indicated.
What you're correspondent says about it is essentially correct. You're looking at a landform, which is ~3-4 SM long, and appears to be inside of a crater body, running along the western wall. It might be a ledge, it might be the result of a landslide due to a secondary impact, etc., etc. That it is natural is a virtual certainty. But the exact nature of what it is will have to wait for future exploration and detailed studies under various lighting condition from high resolution camera equipment.
One thing is also rather certain; there's absolutely nothing in the frame to indicate that it's anything but somewhat unusually shaped.