3. Pre-Main Sequence Heating of Planetoids

Abstract

The problem of thermal metamorphosis of meteorites, possibly the Moon and Mercury, and perhaps other planetary objects is reviewed. Classical mechanisms of heating include fossil nuclides (especially 26Al), accretional heating, tidal heating, chemical reaction heat, and electrical induction. These various mechanisms involve constraints on the early thermal profiles of the Moon or Mercury. In the case of the meteorites, the primary contenders for a viable mechanism currently are fossil nuclides and electromaqnetic induction, or some combination of these. But the issue of energetic mechanisms in the early solar system remains enigmatic. The fossil nuclide hypothesis leads to constraints upon nucleosynthesis while electromagnetic induction places significant constraints upon electrodynamic effects such as solar spin damping.