A Comprehensive 3D Model for Understanding Thermophysical Behaviour of the Moon
Thermophysical measurements of the Moon gained importance in light of recent results from various instruments onboard lunar missions such as LRO, GRAIL and Chandrayaan-1. Although heat flow measurements will be of top priority for future in situ geophysical exploration of the Moon, no such mission is in the offing at least for the next decade. At this point, the only way we can improve our cur-rent understanding about these aspects is through laboratory experiments and numerical simulations. A comprehensive three-dimensional thermophysical model for the Moon has been developed and validated to understand the lunar surface and near subsurface thermophysical behaviour.
It is well known that the surface temperatures of Moon are dictated only by the incident solar heat flux, while the subsurface temperatures vary as a function of a number of parameters viz. latitude, dust cover, density/porosity, morphology, composition and more significantly on the internal heat. The thermophysical behaviour within the uppermost (top few metres) regolith layers is more complex due to their complex geometric, thermal and radiative properties. Furthermore, regional scale topography also significantly influence the heat exchange within the uppermost layer of the lunar surface necessitating a comprehensive finite element model. Using the developed model, simulations have been carried out for a number of synodic periods to derive the diurnal, annual and latitudinal variability of lunar surface and subsurface temperatures and the results were compared with the data reported in literature. Subsurface temperature differences obtained from these simulations have exhibited a significant variability as a function of stratigraphy, composition and latitude. Further, we have made an attempt to understand the role of local topography on the surface and subsurface thermophysical behaviour in the vicinity. Topographic data from LOLA (Lunar Orbiter Laser Altimeter) instrument onboard LRO has been used in conjunction with the model and the surface and subsurface temperatures were derived. Simulations were carried out for few important sites on the Moon that includes Apollo 17 landing site. For validation, results are compared with laboratory experiments, earlier models and Apollo in situ data which showed a very good agreement. Details of the model and results will be discussed.
