Host: The Japanese Society for Planetary Sciences: Local Organizing Committee for 2006 Fall Meeting
It is considered that our solar system was formed from the proto-solar nebula. When protoplanets becomes as massive as the present Mars, they attract the surrounding solar nebula gas and gain solar-type atmospheres (Hayashi et al., 1979; Nakazawa et al., 1985). Mizuno et al. (1980; 1982) calculated the amounts of rare gases captured by the growing proto-Earth. They showed that the proto-Earth captured too much more He and Ne than those exist in the present Earth's atmosphere.
On the other hand, Kominami & Ida (2002) showed that the nebula gas with 10-3~10-4 times of the minimum mass solar nebula (MMSN) model is necessary to damp eccentricities of planets to the present level (order of 0.01). Although this density of the solar nebula gas is much smaller than that of the MMSN model, it is still large enough for the proto-Earth to capture very large amounts of He and Ne.
In order to resolve this problem, we examine the possibility that the gas temperature in a thin solar nebula was much higher than that of previous estimates. Increase in the gas temperature results in increase in the thermal energy of nebula gas compared to the gravitational potential. Thus, it results in order of magnitude decrease of the amount of nebula gas (i.e., He and Ne) captured by the proto-Earth.
