TY - JOUR
T1 - Terrestrial mantle siderophiles and the lunar impact record
AU - Chyba, Christopher F.
N1 - Funding Information:
I thank Carl Sagan, David Grinspoon, and Joe Burns for helpful discussions, and Bill McKinnon and Kevin Zahnle for emphasizing to me the importance of diameter scaling in the transient to final crater transition, I am grateful to Duncan Steel for providing me with data files from and reprints of his most recent work. I thank Ann Blythe for informative discussions about terrestrial geochemistry, Gene McDonald, John Cronin, and John Kerridge for their comments on the water abundance of carbonaceous chondrites, Joe Veverka for keeping me abreast of recent Galileo results, and Norm Sleep and Jay Melosh for critical reviews of an earlier version of this manuscript. This work was supported by NASA Grants NGT-50302 and NAGW-1870.
PY - 1991/8
Y1 - 1991/8
N2 - A simple analytical fit to the lunar cratering record, scaled from final to transient crater diameters, then to impactor masses, implies a total mass ∼1.0 × 1020kg incident on the Moon subsequent to the solidification of the lunar crust ∼4.4 Gyr ago. About half this mass would be retained, and a comparable lunar mass would be eroded. These results are in good agreement with geochemical estimates of the meteoritic component mixed into the lunar crust, which give (0.4-1.5) × 1020 kg. Gravitationally scaling to Earth, and taking account of the statistical probability that the largest impactors incident on Earth were more massive than the largest incident on the Moon, gives an estimate of 1.5 × 1022 kg of material accumulated by Earth subsequent to 4.4 Gyr ago. This result is in excellent accord with geochemical estimates of post-core formation meteoritic input. These estimates, based on abundances of highly siderophile elements in the terrestrial mantle, lie in the range (1-4) × 1022 kg. The significant result is the approximate agreement of the lunar cratering record scaling with both lunar and terrestrial geochemical constraints, numerous uncertainties render exact comparisons pointless. Nevertheless, the close agreement suggests the model developed here may credibly be used to estimate exogenous volatile and prebiotic organic delivery.
AB - A simple analytical fit to the lunar cratering record, scaled from final to transient crater diameters, then to impactor masses, implies a total mass ∼1.0 × 1020kg incident on the Moon subsequent to the solidification of the lunar crust ∼4.4 Gyr ago. About half this mass would be retained, and a comparable lunar mass would be eroded. These results are in good agreement with geochemical estimates of the meteoritic component mixed into the lunar crust, which give (0.4-1.5) × 1020 kg. Gravitationally scaling to Earth, and taking account of the statistical probability that the largest impactors incident on Earth were more massive than the largest incident on the Moon, gives an estimate of 1.5 × 1022 kg of material accumulated by Earth subsequent to 4.4 Gyr ago. This result is in excellent accord with geochemical estimates of post-core formation meteoritic input. These estimates, based on abundances of highly siderophile elements in the terrestrial mantle, lie in the range (1-4) × 1022 kg. The significant result is the approximate agreement of the lunar cratering record scaling with both lunar and terrestrial geochemical constraints, numerous uncertainties render exact comparisons pointless. Nevertheless, the close agreement suggests the model developed here may credibly be used to estimate exogenous volatile and prebiotic organic delivery.
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U2 - 10.1016/0019-1035(91)90047-W
DO - 10.1016/0019-1035(91)90047-W
M3 - Article
AN - SCOPUS:0040139720
SN - 0019-1035
VL - 92
SP - 217
EP - 233
JO - Icarus
JF - Icarus
IS - 2
ER -