Alastair G. W. Cameron, 80, Theorist on Creation of Moon, Dies

From the NYT:

Dr. Cameron's famous work, known as the giant impact theory, holds that a planet roughly the size of Mars struck Earth, sending fragments of Earth's mantle spinning into the atmosphere. The ring of space debris that resulted may have ultimately come together to form the Moon.

Dr. Cameron was a former associate director for planetary sciences at Harvard and was chairman of its astronomy department from 1976 to 1982.

He and others, principally William K. Hartmann of the Planetary Science Institute in Tucson, proposed the impact theory in the 1970's and developed it in later decades. The two scientists had been working independently on the idea when Dr. Hartmann presented his research at a meeting at Cornell in 1974.

The origin of the Moon has been a long standing problem in astrophysics. Lest you think it's been completely solved, there are still arguments about getting all the angular momentum balanced out from Cameron's theory.