Host: The Japanese Society for Planetary Sciences: Local Organizing Committee for 2006 Fall Meeting
Lunar surface and subsurface temperature were measured in Apollo 15, 17 missions for lunar surface heat-flow value. Thermal diffusivity k of the lunar regolith was estimated to be 1.0E-8(m^2/s) by the analysis of annual temperature change (Langseth et al., 1976). From the analysis of the eclipse and lunar night time cooling-down curves, the existence of a thin layer (2cm, k=1.0E-9(m^2/s)) on the lunar surface was predicted. (Keihm et al., 1973).
Shorter periodic temperature change has better resolution to the thermal properties for its smaller thermal skin depth.
We analyzed the temperature history data in lunation and lunar eclipse which have shorter period compared to annual one. We could make the observed Lunation amplitude when we computed by 1-layered model whose thermal properties were uniform (k=1.0E-8). We should have postulated 2-layered model to explain the eclipse data (Takita et al., 2006). In the model calculations we set the k of the upper layer 1.0E-9(m^2/s) and the lower to be 1.0E-6(m^2/s), the eclipse-model amplitude matched the Apollo data when the thickness of the upper layer was about 2mm. Thus the value of k could be ten times bigger than the annual result.
