December 1, 2008

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Highland Wrinkle Ridge

image from Lunar Orbiter IV-11-h1 LPI Lunar Orbiter Photo Gallery

Kugler is an old, 65 km wide, mare-flooded crater that is part of Mare Australe on the farside beyond Lyot. It is crossed by a typical mare ridge that remarkably seems to continue another 60 km across highlands to the crater Anuchin. In this Orbiter image the ridge appears as a narrow crease until it reaches an old crater that seems to be missing its left (western) side. On closer look the ridge crosses the middle of the crater with a bright scarp facing east. This shows that the material to the left of the ridge is higher than the smoother material on the east half of the crater. The left half of the crater is indistinguishable from the adjacent highlands. If this were an image of Mercury scientists would say that this is another example of a low angle thrust fault formed as the planet cooled and contracted. But this is the Moon. However, the same explanation may apply here. Twenty-three years ago Alan Binder noticed a number of similar faults in the highlands and suggested that they were very young and might be faults due to the Moon's late stage cooling and shrinking. If this interpretation is correct much larger Moonquakes than sampled by the Apollo era seismometers might periodically occur. The very high resolution images from the forthcoming Lunar Reconnaissance Orbiter and other current orbiters will allow more comprehensive detection and mapping of these faults.

Chuck Wood

Technical Details
Mare ridges used to be called wrinkle ridges, and that term may be more appropriate for ones that cross highlands.

Related Links
Clementine Atlas plate 130

Yesterday's LPOD: Pyrenees Perusal

Tomorrow's LPOD: Postcards From the Lucky


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