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Consequences of Giant Impacts on Early Uranus for Rotation, Internal Structure, Debris, and Atmospheric Erosion

Kegerreis, J.A.; Teodoro, L.F.A.; Eke, V.R.; Massey, R.J.; Catling, D.C.; Fryer, C.L.; Korycansky, D.G.; Warren, M.S.; Zahnle, K.J.

Consequences of Giant Impacts on Early Uranus for Rotation, Internal Structure, Debris, and Atmospheric Erosion Thumbnail


Authors

L.F.A. Teodoro

R.J. Massey

D.C. Catling

C.L. Fryer

D.G. Korycansky

M.S. Warren

K.J. Zahnle



Abstract

We perform a suite of smoothed particle hydrodynamics simulations to investigate in detail the results of a giant impact on the young Uranus. We study the internal structure, rotation rate, and atmospheric retention of the post-impact planet, as well as the composition of material ejected into orbit. Most of the material from the impactor's rocky core falls in to the core of the target. However, for higher angular momentum impacts, significant amounts become embedded anisotropically as lumps in the ice layer. Furthermore, most of the impactor's ice and energy is deposited in a hot, high-entropy shell at a radius of ~3 R ⊕. This could explain Uranus' observed lack of heat flow from the interior and be relevant for understanding its asymmetric magnetic field. We verify the results from the single previous study of lower resolution simulations that an impactor with a mass of at least 2 M ⊕ can produce sufficiently rapid rotation in the post-impact Uranus for a range of angular momenta. At least 90% of the atmosphere remains bound to the final planet after the collision, but over half can be ejected beyond the Roche radius by a 2 or 3 M ⊕ impactor. This atmospheric erosion peaks for intermediate impactor angular momenta (~3 × 1036 kg m2 s−1). Rock is more efficiently placed into orbit and made available for satellite formation by 2 M ⊕ impactors than 3 M ⊕ ones, because it requires tidal disruption that is suppressed by the more massive impactors.

Citation

Kegerreis, J., Teodoro, L., Eke, V., Massey, R., Catling, D., Fryer, C., …Zahnle, K. (2018). Consequences of Giant Impacts on Early Uranus for Rotation, Internal Structure, Debris, and Atmospheric Erosion. Astrophysical Journal, 861(1), Article 52. https://doi.org/10.3847/1538-4357/aac725

Journal Article Type Article
Acceptance Date May 18, 2018
Online Publication Date Jul 2, 2018
Publication Date Jul 2, 2018
Deposit Date Jul 9, 2018
Publicly Available Date Jul 10, 2018
Journal Astrophysical Journal
Print ISSN 0004-637X
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 861
Issue 1
Article Number 52
DOI https://doi.org/10.3847/1538-4357/aac725
Related Public URLs https://ui.adsabs.harvard.edu//#abs/2018ApJ...861...52K/abstract

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Copyright Statement
© 2018. The American Astronomical Society. All rights reserved.







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