Explanation:

The November 6 LPOD featured an image by Jim Phillips of a little known linear feature east of Neander. Based on the observation that it cast a shadow at sunrise, and exhibited a bright reflection near sunset, I proclaimed it to be a fault. But KC Pau also took an image with larger scale on the same night as Jim, providing additional information that causes me to reconsider the fault interpretation. A fault is often a simple break of the crust where one side has moved relative to the other. At the Straight Wall, for example, the eastern side has moved up 300-400 m compared to the western side. The fact that this Neander feature casts a shadow westward at sunrise shows that its eastern side is higher than the western side. But KC's image clearly shows that a thin shadow is also cast eastward (to the right) near sunset! Additionally, the area just west (left) of the bright scarp area is also in shadow. These two observations suggest that this feature may be a rille, whose sides are of uneven height. But a Lunar Orbiter IV photo, taken with opposite lighting and higher sun than KC's image, provides little evidence that its a rille. I am willing to accept the evidence from all these sources and speculate that this may be a very narrow V-shaped rille whose east side is higher than its west. This would be somewhat similar to the fault that turns into a rille on the south side of Lacus Mortis.

— Chuck Wood

Technical Details:
31 Oct, 2004. 10" Newtonian + 5X barlow

Related Links:
Rukl Atlas of the Moon, Sheet 68

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