This grand valley is called the "Alpine Valley" as it is located within the alpes on the surface of the moon. The origin was heavily discussed and still it is not certain, what might have caused it. For a long time it was said to be a remnant of a severe impact of a meteorit that once hit the moon at high velocity and in a very shallow angle. Be it as it will, the valley is some 166km long and measures around 10km in width. It caneasily be observed in a moderate amateur telecope in the northern hemisohere of the moon.

However more recent investigations suggest this valley to be the result of either tectonic or volcanic activity. The full size image shows a quite narrow rill on the bottom of the alpine valley that suits the idea of a tectonic or volcanic origin much better, that an impact theory could ever explain. Suggestions indicate this narrow groove to be 1km in width. This feature is a most difficult target for a telescope.