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Geophysical consequences of planetary-scale impacts into a Mars-like planet

Marinova, Margarita M. and Aharonson, Oded and Asphaug, Erik (2011) Geophysical consequences of planetary-scale impacts into a Mars-like planet. Icarus, 211 (2). pp. 960-985. ISSN 0019-1035.

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All planetary bodies with old surfaces exhibit planetary-scale impact craters: vast scars caused by the large impacts at the end of Solar System accretion or the late heavy bombardment. Here we investigate the geophysical consequences of planetary-scale impacts into a Mars-like planet, by simulating the events using a smoothed particle hydrodynamics (SPH) model. Our simulations probe impact energies over two orders of magnitude (2 × 10^(27)–6 × 10^(29) J), impact velocities from the planet’s escape velocity to twice Mars’ orbital velocity (6–50 km/s), and impact angles from head-on to highly oblique (0–75°). The simulation results confirm that for planetary-scale impacts, surface curvature, radial gravity, the large relative size of the impactor to the planet, and the greater penetration of the impactor, contribute to significant differences in the geophysical expression compared to small craters, which can effectively be treated as acting in a half-space. The results show that the excavated crustal cavity size and the total melt production scale similarly for both small and planetary-scale impacts as a function of impact energy. However, in planetary-scale impacts a significant fraction of the melt is sequestered at depth and thus does not contribute to resetting the planetary surface; complete surface resetting is likely only in the most energetic (6 × 10^(29) J), slow, and head-on impacts simulated. A crater rim is not present for planetary-scale impacts with energies >10^(29) J and angles ≤45°, but rather the ejecta is more uniformly distributed over the planetary surface. Antipodal crustal removal and melting is present for energetic (>10^(29) J), fast (>6 km/s), and low angle (≤45°) impacts. The most massive impactors (with both high impact energy and low velocity) contribute sufficient angular momentum to increase the rotation period of the Mars-sized target to about a day. Impact velocities of >20 km/s result in net mass erosion from the target, for all simulated energies and angles. The hypothesized impact origin of planetary structures may be tested by the presence and distribution of the geochemically-distinct impactor material.

Item Type:Article
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Aharonson, Oded0000-0001-9930-2495
Additional Information:© 2010 Elsevier Inc. Received 20 September 2009; revised 23 September 2010; accepted 30 October 2010. Available online 11 November 2010. We thank Robin Canup, Paul Asimow, Andy Ingersoll, and Dave Stevenson for insightful discussions and dedicated help. This work was supported by a Henshaw Fellowship, an NSERC post-graduate fellowship, and a Canadian Space Agency supplement.
Funding AgencyGrant Number
Henshaw FellowshipUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Canadian Space Agency (CSA)UNSPECIFIED
Subject Keywords:Impact processes; Cratering; Mars; Accretion
Issue or Number:2
Record Number:CaltechAUTHORS:20110315-151113842
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Official Citation:Margarita M. Marinova, Oded Aharonson, Erik Asphaug, Geophysical consequences of planetary-scale impacts into a Mars-like planet, Icarus, Volume 211, Issue 2, February 2011, Pages 960-985, ISSN 0019-1035, DOI: 10.1016/j.icarus.2010.10.032. (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:22911
Deposited By: Jason Perez
Deposited On:15 Mar 2011 22:55
Last Modified:03 Oct 2019 02:41

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