THERMAL BEHAVIOR OF ROCKS ON LUNAR SURFACE

The thermal behavior of rocks with sizes between 3 millimeters and 3 meters resting on the lunar equator is analyzed during both lunation and eclipse assuming that they emit and absorb radiation according to the Stefan-Boltzmann law. Thermal parameters for the rocks are taken as those of a typical basalt, a choice consistent with the interpretation of the Luna X γ-ray experiment. Submeter ({less-than or approximate}10 cm) rocks are found to be approximately isothermal throughout lunation and eclipse, while meter-size rocks show markedly different temperatures on different faces during lunation (no analysis was carried out for eclipse). Thermal heat exchange between rock and lunar soil is negligible for meter rocks during lunation (and eclipse) and submeter rocks during eclipse, but is significant during lunation for rocks {less-than or approximate}10 cm. Partial imbedding of submeter rocks tends to reduce the rock-soil temperature differential during lunation and to keep them warmer than exposed rocks during eclipse. The presence of neither submeter rocks (with size distributions as observed by Surveyor I and III) nor meter rocks should have large effects on Earth-based thermal measurements during lunation. During eclipse, submeter rocks can produce small but detectable variations in both Earth-based and direct, local spacecraft environs measurements. Meter rocks near a spacecraft may emit ∼10 times the energy of the surface viewed at lunar sunrise or sunset and hence must be reckoned with when local thermal measurements are interpreted. © 1968.