Microcraters on Apollo 15 and 16 rocksMicrocrater frequency distributions, determined for 11 Apollo 16 rocks and three Apollo 15 rocks, fall into four categories. Category 1 rocks (68415, 68416, 62235) are angular, cratered on one side only, and have moderate crater densities. Category 2 rocks (60016, 66075, 61175) are subrounded, cratered on all sides, and have distributions suggestive of the steady state. Category 3 rocks (61015, 62295) are subangular and cratered on only one side, but the crater frequency distributions have some of the characteristics of category 2 rocks. Category 4 rocks (15015, 15017, 15076, 60335) are angular, cratered on only one side, and have moderated to very low crater densities. The crater frequency distributions of categories 1 and 4 have properties indicating the possibility of estimating the time they were exposed to micrometeor bombardment. Category 1 rocks appear to have been exposed for 2 to 3 m.y. These rocks, particularly 68415, 68416, and 69935, may be ejecta from South Ray Crater, indicating an age of 2 to 3 m.y. for South Ray Crater. Category 4 rocks have been exposed for much shorter periods.
Document ID
19740040280
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Morrison, D. A.
Mckay, D. S.
Fruland, R. M. (NASA Johnson Space Center Houston, Tex., United States)
Moore, H. J. (U.S. Geological Survey Menlo Park, Calif., United States)