Gravitational instability in two-phase disks and the origin of the moon
AbstractTwo-phase disks may be gravitationally unstable at temperatures or surface densities at which a disk composed of either single phase would be highly stable. It is argued that two-phase disks can achieve a marginally unstable state (in addition to a highly unstable state that leads to fragmentation), limited by the ability of the photosphere to radiate the energy dissipated in the disk. A self-consistent prescription for the viscosity induced by the slow instabilities is provided. Two-phase disks are more centrally condensed than single-phase disks, and their secular cooling time may be comparable to their spreading time. A circumterrestrial disk of sufficient mass to form the moon provides a detailed example of all the preceding points. Its stability, structure, and dynamical evolution are investigated, and it is concluded that its spreading time is short (about ~100 yr); the moon is formed molten, or partially molten; the moon's initial orbit lies in the earth's equatorial plane; and only a small fraction of the disk mass is lost in a wind, although this may represent a substantial fraction of volatiles. Most of these conclusions are independent of how the disk was formed, e.g., from a giant impact.
Thompson, Christopher and Stevenson, David J. (1988) Gravitational instability in two-phase disks and the origin of the moon. Astrophysical Journal, 333 . pp. 452-481. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20130621-152608690 <http://resolver.caltech.edu/CaltechAUTHORS:20130621-152608690>