Obliquely Viewed Fault

Originally published July 30, 2004

Image Credit: Apollo 16-120-19224

Obliquely Viewed Fault

One of the most famous features on the Moon - certainly as judged by the number of image submissions to LPOD - is the Straight Wall. Until chancing upon this image in the online Apollo Image Atlas at the Lunar & Planetary Institute, I though that the Wall had not been photographed during the Apollo program. I don't know why this shot has not been widely used because it is great! From the 110 km altitude of the Apollo 16 Command Module the Wall appeared near the southern horizon, allowing this unique oblique view taken with the handheld Hasselblad camera. Along the skyline (spaceline?) is the rim of the half crater (that I call Ancient Thebit) whose floor is cut by the Straight Wall. The foreground shows the wrinkle ridges that continue the rim of the 225 km wide Ancient Thebit as a ghost half crater. Clearly the lavas of Mare Nubium are younger (because they hold far fewer small impact craters) than those that fill Ancient Thebit. The trace of the 400 m high Straight Wall appears curved, as if the floor of Ancient Thebit is bowed up. And the dome that is the source of the Birt Rille is very low - domes really do have shallow slopes..