Apollo 11 soil mechanics investigation.

The fine-grained surface material at the Apollo 11 landing site is a brownish, medium-gray, slightly cohesive granular soil, with bulky grains in the silt-to-fine-sand range, having a specific gravity of 3.1 and exhibiting adhesive characteristics. Within the upper few centimeters, the lunar soil has an average density of about 1.6 grams per cubic centimeter and is similar in appearance and behavior to the soils studied at the Surveyor equatorial landing sites. Althouglh considerably different in composition and in range of particle shapes, it is similar in its mechanical behavior to terrestrial soils of the same grain size distribution.