A previous model is extended to include the effects of the disappearance of craters caused by filling by dust or lava. Both the age distribution and expected number density of lunar craters are obtained as functions of crater diameter and of time. These results are applied to the meteoroidal impact hypothesis of the origin of lunar craters. Good agreement is obtained with observed number densities on the lunar continents and maria. It is assumed that the rate of filling of craters on the continents corresponds to the rate of meteoritic accretion, and the rate of filling on the maria is 50 to 100 times larger than on the continents, corresponding to filling of mare craters by lava. (See also RM-4681-PR.) 39 pp. Bibliog.
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