Apollo 17 “Orange Soil” and Meteorite Impact on Liquid Lava

Abstract

THE “orange soil” from Shorty Crater differs greatly from ordinary lunar soils in that it consists of ∼99% 10–300 µm smooth shiny spherules and broken fragments of spherules of transparent orange glass, about 20% of which contain partly crystallized to opaque material. The remaining 1 % is chiefly crystalline basalt fragments. Although the colour of the individual orange spherule varies with thickness from yellow–orange to red–brown, all orange glass in our sample (74220, 70; 0.25 g) has a uniform index of refraction (∼ 1.712). By contrast, other lunar soils contain spherules ranging from 1.50 to 1.75. The orange glass is also completely free of bubbles, to the limit of resolution of the light microscope, whereas bubbles are present in many other spherule samples. The spherules generally appear spherical in a normal microscope mount, but when viewed from two directions many are found to be oblate spheroids with axial ratios varying from near 1.00 to as low as 0.42 (Fig. 1a). Some have fissioned during free flight¹ and all stages of the fission process are found, as described for the Apollo 11 samples. Only a few spherules seem to have been distorted by landing while still soft. One notable exception is the occurrence of small spherules of orange glass conforming and adhering to the surface of larger black spherules (Fig. 1b).