Physical Sciences: Cracking of Lunar Mare Soil

Abstract

THE tendency of lunar soil to break into clods when disturbed was recognized from Surveyor 1 photographs^1,2. Pictures of disturbances produced in bearing tests with the Surveyor 3 soil mechanics surface sampler³ suggested to some observers that the soil layer in Oceanus Procellarum tends to crack into thin flat “tiles” (Figs, 1a and 2a) and, therefore, that it consists of a thin, rather rigid crust over a softer substrate. Pictures of areas disturbed by the Apollo 11 closeup camera in Mare Tranquillitatis (Fig. 3a) and by the Apollo 12 lunar module descent engine in Oceanus Procellarum conveyed a similar impression^4,5. None of the authors of these works were misled, and, indeed, they warned against this interpretation^3–5. Nevertheless, photographs made by the Apollo 12 astronauts of the areas disturbed by Surveyor 3 help to clarify the matter.