Young Fractures?

Originally published September 20, 2004

Image Credit: Apollo 17 Pan Camera AS17-2313

Young Fractures?

Apollos 15 through 17 carried Panoramic Cameras which acquired thousands of photographs with resolutions up to 2 m. Some of these pictures show tiny details not seen elsewhere. Here is an example from the "Apollo Over the Moon: A View from Orbit" book. This image appears on page 208 and is said to show a gash or fracture in the Littrow rilles on the eastern shore of Mare Serenitatis. Based on the scale bar given in the book, the area shown is 50 km wide. That is obviously in error (the craters have morphologies common in craters 100s of meters wide) - I would guess the picture width is only 1-2 km. In the book's figure caption, no origin is suggested for this gash, but its fresh appearance suggests it must be very young. This is clearly not a feature that formed when the lava surface did, so it is not a lava flow channel or rille. And most lunar fracturing - such as formed concentric and linear rilles - stopped by 3.6 billion years ago. From Apollo seismometers we have learned that the Moon continues to experience small moonquakes. And it has been suggested that some quakes are large enough to rupture the lunar surface. Perhaps this gash is an evidence for a continuing seismic hazard on the Moon!