Large scale lunar horizon glow and a high altitude lunar dust exosphere

Abstract

All three Apollo 17 astronauts sketched a “lunar horizon glow,” seen from orbit above the Moon. It is shown that the shape of the glow is compatible with scattering of sunlight off of gas or dust at high altitudes above the Moon. Our mathematical modeling best simulates the glow with submicron dust grains whose spatial density varies with altitude above the Moon as exp(‐H/H s ), where H s is in the range of 5 to 20 km. These dust grains are probably electrically charged and ejected above the lunar surface by local electric fields.