Accretion to Earth and Moon ∼3.85 Ga

  • Stephen J. Mojzsis
  • Graham Ryder


The lunar record provides a means of estimating post-accretionary impact influences on the early Earth and a comparison with what we can more directly infer from the Earth’s own rocks. In the period from about 3.9 to about 3.8 Ga there was considerable impacting on the Moon with evidence for concurrent marine sedimentation on Earth. This was a time interval in which the impactor flux to the lunar surface was orders of magnitude greater than the present rate; massive impacts as well as an enhanced background flux of extraterrestrial matter should have likewise affected the surface of early Earth. As yet, no unequivocal evidence for a “Late Heavy Bombard- ment of the Earth” has been established from direct measurement of terrestrial crustal rocks. The lack of a signal of the bombardment on Earth may be due to the fact that: (i) the oldest sediments do not overlap with the bombardment era, (ii) the bombard- ment was less intense than previously thought, (iii) sedimentation was extremely rapid so as to dilute any extraterrestrial signal, (iv) sample volumes yet analyzed under- sample extra-terrestrial input, or (v) windows for sampling elevated fluxes of extrater- restrial bodies were very short between long periods of relative calm. Further exten- sive studies of the oldest known sediments will be needed to resolve the issues raised in this paper.


Detrital Zircon Platinum Group Element Banded Iron Formation Lunar Planet Magma Ocean 
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© Springer Science+Business Media New York 2001

Authors and Affiliations

  • Stephen J. Mojzsis
    • 1
  • Graham Ryder
    • 2
  1. 1.University of CaliforniaLos AngelesUSA
  2. 2.Lunar and Planetary InstituteHoustonUSA

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