Lunar Orbiter Photographs: Some Fundamental Observations: Preliminary study reveals details of craters, crater distributions, and the major types of terrain

• Published in: Science (American Association for the Advancement of Science) Vol. 158; no. 3808; pp. 1529 - 1535
• Main Authors: Trask, N J, Rowan, L C
• Format: Journal Article
• Language: English
• Published: United States 22-12-1967
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.158.3808.1529

High-resolution photographs returned by Orbiters II and III typically show a surface pitted with small, perfectly circular craters as much as 50 meters in diameter, some of which are strongly clustered; these are superposed on larger, generally shallower craters and must be a mixture of primary and secondary impact craters. Rough terrain is less heavily cratered but is crossed by numerous closely spaced troughs and ridges up to 3 meters high. Terraces, which commonly occur at the base of steep slopes, are also crossed by these troughs and ridges and have relatively few craters. Fresh craters-craters whose exterior slopes are covered with material different from that of the intercrater areas-are rare and are surrounded by angular blocks up to 80 meters in diameter, in varying numbers; these craters apparently undergo gradual destruction to shallow gentle depressions. The frequency of craters 100 meters and more in diameter varies widely, even on level terrain; some of the highest concentrations of craters occur on rays.