A collisional origin to Earth's non-chondritic composition?

Amy Bonsor*, Zoë M. Leinhardt, Philip J. Carter, Tim Elliott, Michael J. Walter, Sarah T. Stewart

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

51 Citations (Scopus)


Several lines of evidence indicate a non-chondritic composition for bulk Earth. If Earth formed from the accretion of chondritic material, its non-chondritic composition, in particular the super-chondritic 142Nd/144Nd and low Mg/Fe ratios, might be explained by the collisional erosion of differentiated planetesimals during its formation. In this work we use an N-body code, that includes a state-of-the-art collision model, to follow the formation of protoplanets, similar to proto-Earth, from differentiated planetesimals (>100km) up to isolation mass (>0.16M). Collisions between differentiated bodies have the potential to change the core-mantle ratio of the accreted protoplanets. We show that sufficient mantle material can be stripped from the colliding bodies during runaway and oligarchic growth, such that the final protoplanets could have Mg/Fe and Si/Fe ratios similar to that of bulk Earth, but only if Earth is an extreme case and the core is assumed to contain 10% silicon by mass. This may indicate an important role for collisional differentiation during the giant impact phase if Earth formed from chondritic material.

Original languageEnglish
Pages (from-to)291-300
Number of pages10
Publication statusPublished - 1 Feb 2015


  • Abundances, interiors
  • Collisional physics
  • Planetary formation
  • Planetesimals


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