Crater Frequency and the Interpretation of Lunar History.

摘要

The significance of lunar crater frequencies as a function of crater diameter was investigated. It was concluded that the absolute ages of isochronous surfaces previously determined by this technique are not valid. Relative ages can be obtained from crater frequencies when account is taken of complications caused by secondary and, perhaps, igneous craters, and obliteration of old craters by younger ones. Studies made at AFCRL indicate that the maria are of similar, but not identical ages, and that some maria may contain surfaces of different ages. They also indicate that the Apenninian debris sheet is older, but not much older, than the maria. The present surface of the crater Ptolemaeus is evidently composed of either Apenninian debris, or Procellarian material. It was concluded that craterfrequency is a useful stratigraphic tool. (Author)