Condensation and Formation of Ice on Planets as a Consequence of Gravity

The planets in the Solar System formed as a result of accretion of planetesimals and other particles that condensed out of the solar nebula. The condensation from the solar nebula can be affected by the enhancement of the gas pressure near a forming planetary embryo because of its gravity. Thus, the location of condensation of a particular ice depends not just on distance from the Sun but also on the presence of an embryo. This phenomenon of gravitationally assisted condensation takes place when the following conditions are met—A large enhancement of surface pressure over nebula pressure and a small enhancement of surface temperature over nebular temperature. We can consider an isothermal state, when the surface and nebular temperature is nearly equal. The accretion of an ice shell around the planetary embryo is affected by the gravitational energy of these self-gravitating bodies as well as the release of latent heat, both of which determine the surface temperature. For instance for an embryo of radius 887 km at T = 160K, an ice shell of water is accreted at a rate of 3.23×10¹⁴ kg/yr. Additionally , as the size of the body increases over time, the surface temperature of the embryo changes. The accretion rate determines the significance of this phenomenon in producing a snowfall of different volatiles on the body.