1. One can also think of this as the energy required to disburse permanently a fragmented planet of mass M and radius R. [See Endnote 116 on page 337 and related paragraphs.]
2. George W. Wetherill, “Occurrence of Giant Impacts during the Growth of the Terrestrial Planets,” Science, Vol. 228, 17 May 1985, p. 879.
3. “... the critical heat flow for the onset of a runaway is around 1.4 solar constants (where 1 represents the present solar input at Earth).” David J. Stevenson, “Greenhouses and Magma Oceans,” Nature, Vol. 335, 13 October 1988, pp. 587–588.
4. Ibid.