Mick West said: This makes me think it's an artifact from two images being stitched together, images that were taken at different times.



It's also possible that the pixels near the join were stretched a little. Click to expand...

The moon is something of a pet subject of mine, so I can give chapter and verse on this one.Google Moon images are taken from a number of sources, most of which are old analogue photographs.This particular frame is from the mapping camera on Apollo 15, back in 1971. This camera was part of the Scientific Instrument Module mounted on the Service Module which remained in orbit around the moon while the Lunar Module landed on the moon. http://www.lpi.usra.edu/lunar/missions/apollo/apollo_15/experiments/ The mapping camera took around 2000 images of the lunar surface, and every single one of them (as far as I can see) features this object in the same area of the frame. It is a piece of debris (hair/fluff) in the optics of the camera, likely held close to the film plane as it is fairly sharp and appears to cast a shadow.Here is an animated GIF of just four of those frames showing the "object" appearing in different places on the moon.The exact frame used on Google Moon appears to be this one, captured from an altitude of 100.89km above the surface: http://wms.lroc.asu.edu/apollo/view?image_name=AS15-M-1151&popup=true You can zoom in on the image and see the bit of fluff. This screenshot shows you the area to zoom in on (blue square). Note that the image in the OP is rotated through 90 degrees.