The effect of pulverization on the albedo of lunar rocks

Abstract

Measures of the albedo under full-moon conditions have been made on two samples of very dark rocks, pulverized and sieved so as to obtain powders of different grain size. Below a size of 0.05 mm the albedo suddenly increases, obviously because the individual grains become transparent. By a rough calculation of the radiation transfer this is made understandable and a relation is found between the grain size and the absorption coefficient necessary to produce in combination an albedo of 0.10. If the Moon is covered by fine dust, its low albedo shows that the absorption coefficient must be very high, probably because of darkening by the solar wind.