AS17-150-22959(H)

Figure 20

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The very large "twin crater" in this southward-looking oblique view is Van de Graaff, approximately 250 km in length. The dark oval area in the upper right corner near the horizon is the mare-filled crater Thomson, which in turn lies within a much larger mare-filled circular basin that contains Mare Ingenii. The crater Van de Graaff itself is filled with both light plains and mare materials. The darker patch at the near end is mare material, and the hummocky material along its left (east) side is ejecta from the crater Birkeland (B). Light plains materials are also visible in the near field within smaller craters and in areas between them. This region of the lunar far side is of particular interest for two reasons: (1) it has the highest concentration of natural radiation yet recorded on the lunar far side by the gamma ray spectrometer (Metzger et al., 1973), and (2) it is also the site of the most prominent magnetic anomaly associated with the far-side highlands (Coleman et al., 1972a).  -F.E.-B.