Several mechanisms have been proposed for the Moon's formation 4.527 ± 0.010 billion years ago,[i] some 30–50 million years after the origin of the Solar System.[15] Recent research presented by Rick Carlson indicates a slightly younger age of between 4.40 and 4.45 billion years.[16] [17] These mechanisms included the fission of the Moon from Earth's crust through centrifugal force[18] (which would require too great an initial spin of Earth),[19] the gravitational capture of a pre-formed Moon[20] (which would require an unfeasibly extended atmosphere of Earth to dissipate the energy of the passing Moon),[19] and the co-formation of Earth and the Moon together in the primordial accretion disk (which does not explain the depletion of metallic iron in the Moon).[19] These hypotheses also cannot account for the high angular momentum of the Earth–Moon system.[21]