rupes recta

The best known of all lunar faults, its official name means "straight fault", but its common name is Straight Wall. During the 19th century its artificial appearance earned it the name The Railway. It was once thought to be a vertical cliff, but more recent measurements show it to be a slope, variously estimated at between 15° and as much as 41° (which would still make it one of the steepest slopes on the visible face of the Moon).

Photo: Thierry Legault. The full size original of this and other high definition lunar images may be seen at his High Resolution CCD Imaging site.

Inconstant Moon