Most workers in the cosmogony business take it for granted that the Moon formed from the remnants of an impact between the early Earth and a Mars-mass object, usually called ‘Theia’. But that’s not the only theory. Throughout the 1970s and 1980s, in parallel to the Big Impact research effort, Robert Malcuit of Denison University was working on a Capture theory for the Moon’s origins, in an effort to explain its curious refractory rocks and the odd pattern of maria on its nearside face.
Of course, in hindsight, one can see the Capture origin idea was eclipsed by the simulation successes that Big Impact theorists have had, and the fairly strong direct geochemical evidence for kinship between Earth and Moon rocks. However not everything is so easily explained by the Big Impact and it’s by no means a ‘proven’ theory of Moon origin, merely a very good one. Science advances by distinguishing betweening good competing theories via experimental tests. But what discriminates between possible events that occurred about 4 billion years ago?
More later.
Relevant links…
MSNBC: Controversial moon theory rewrites history
Robert Malcuit’s page at Denison U…
Science News report from 1987…
Denison U Magazine piece 2007…
NASA ADS entry on ‘Robert Malcuit’…
ADDENDUM:
Abstracts from the GSA 2009 meeting…