The terrestrial late veneer from core disruption of a lunar-sized impactor
Abstract
Overabundances in highly siderophile elements (HSEs) of Earth's mantle can be explained by conveyance from a singular, immense (D ∼ 3000 km) ;Late Veneer; impactor of chondritic composition, subsequent to lunar formation and terrestrial core-closure. Such rocky objects of approximately lunar mass (∼0.01 M⊕) ought to be differentiated, such that nearly all of their HSE payload is sequestered into iron cores. Here, we analyze the mechanical and chemical fate of the core of such a Late Veneer impactor, and trace how its HSEs are suspended - and thus pollute - the mantle. For the statistically most-likely oblique collision (∼45°), the impactor's core elongates and thereafter disintegrates into a metallic hail of small particles (∼10 m). Some strike the orbiting Moon as sesquinary impactors, but most re-accrete to Earth as secondaries with further fragmentation. We show that a single oblique impactor provides an adequate amount of HSEs to the primordial terrestrial silicate reservoirs via oxidation of (<m-sized) metal particles with a hydrous, pre-impact, early Hadean Earth.
- Publication:
-
Earth and Planetary Science Letters
- Pub Date:
- December 2017
- DOI:
- 10.1016/j.epsl.2017.09.041
- arXiv:
- arXiv:1709.07554
- Bibcode:
- 2017E&PSL.480...25G
- Keywords:
-
- Late Veneer;
- SPH models;
- Hadean Earth;
- highly-siderophile elements;
- mantle;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Accepted for publication in Earth and Planetary Science Letters, 17 pages, 4 figures