Peter Schultz, the author of the book Moon Morphology, spends some time discussing the only large crater which seems to have a slightly raised rim in frame LO-2-56H2, and therefore would seem to be an impact-related feature. But Schultz notes a puzzling lack of any sign of ejecta from this crater. Also, though this crater does have raised rim, it is only slightly so. This would not be surprising for an old crater, but this crater is not shallow as would be expected of an old crater, but deep and cone shaped as would be expected of a young crater.

[crater image]
This image is from frame number LO-2-56H2 as obtained from the NSSDC.  The image is oriented with north to the left and the sunlight coming from the top,  which is east. The sun was low in the sky, about fifteen degrees above the horizon.  The crater is roughly one-half mile  across.  The debris is to the right of  the rim's shadow.

Schultz refers to "numerous dimple craters and linear depressions" surrounding the crater. Some of these linear depressions (lower left) run right up to the crater's rim. In fact, there are many of these linear depressions in this region. All of them are oriented in the same direction. The author does not mention the fact there are smaller but similarly oriented linear depressions on the crater's floor. The dimple craters are interesting because they may indicate areas where the regolith has sifted down into an underlying cavity. With all the collapse features, linear depressions, and dimple craters, this was an area which begged closer scrutiny, particularly the crater itself.

[Debris Field]
An overall view of the debris, enlarged from the above image. This area is approximately 1/8 mile across. Note the diagonal gridlike trending of the debris.

Perturbing Craters The First Crater Arago C Lunar Orbiter


Anomalous crater debris in Lunar Orbiter images of the Sea of Tranquility on the Moon - a deep unnamed crater which has few indications of an impact feature and is surrounded by odd linear depressions. The debris exhibits peculiar diagonal gridlike tendencies that would not be expected in debris formed by natural processes.