Anomalous cooling of a cratered lunar surface

Infrared observations of the moon have indicated that a considerable number of craters and maria exhibit an enhanced thermal emission during an eclipse. We suggest that a contributing factor to these anomalies may be regions densely covered with deep craters of centimeter dimensions. A model of a cratered surface is constructed which consists of spherically shaped craters distributed across a flat surface. In analyzing the thermal behavior of a crater, the effects of reradiation, conduction, shadowing, and local incidence angle are considered. A numerical calculation of the cooling of a surface covered with hemispherical craters indicates that an anomalous temperature of 30°K is produced during an eclipse. An extension of the model to craters with a depth to diameter ratio of 2 produces a 70°K anomaly. It is concluded that additional observations are needed to distinguish between the various models which have been proposed to account for the thermal anomalies.