Thermal Radiation from the Moon and the Heat Flow Through the Lunar Surface

Abstract

Observations of thermal radiation from the Moon at a frequency of 178 Mc/s are described, giving a value for the mean disk temperature of 233 ± 8 °K, which is the same to within 25 °K as various estimates of the mean disk temperature at the surface. The absence of any detectable steady temperature gradient through the surface leads to upper limits on the steady heat flow from the Moon for a range of possible properties of the surface materials. The observations at shorter radio wavelengths favour a model in which a gravelly material extends to depths of at least several metres. For this model the upper limit to the heat flow is very close to that expected from radioactive decay in a Moon of chondritic composition.