Ranger Photographs of the Moon


  • N. J. Trask


Photographs from the Ranger probes provided the first direct evidence on the fine-scale topography of the moon and showed that the surface is relatively smooth over slope distances of 1 meter. In addition to craters, elements contributing to the topography at this scale are the closely spaced ridges and troughs of lunar patterned ground. Blocks in the size range 0.5 meters to several meters were not seen in the Ranger pictures, perhaps because of the limited sampling at three widely separated points. Ranger 7 photographs showed the pre-ponderance of shallow elongate to circular craters along rays. Ranger 8 photographs were notable for portraying with new clarity the craters Sabine and Ritter, which appear to be of internal rather than impact origin. Ranger 9 photographs of the floor of the crater Alphonsus contained data from which a complicated geologic history of the floor can be deciphered.