37th DPS Meeting, 4-9 September 2005
Session 3 Asteroids I
Oral, Monday, September 5, 2005, 11:00am-12:30pm, Law LG19

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[3.04] Impact Cratering, Mantle Removal, and Catastrophic Disruption of Differentiated Asteroids

E. Asphaug, C. Agnor (UCSC)

We present results from impact simulations, applying a version of the SPH hydrocode (Benz 1990) used in recent planetary collisional studies (e.g. Canup & Asphaug, Nature 2001; Agnor & Asphaug, Ap.J. 2004) to examine the impact evolution of differentiated asteroids. We use 4 Vesta as an archetype to connect this research to previous modeling (Asphaug M&PS 1997). We also extend our simulations to larger (1000 km) and smaller (200 km) targets, and span velocity regimes from subsonic (0.5 km/s) to hypervelocity (10 km/s), in order to complement previous impact studies by Benz & Asphaug (Icarus 1999), who focused on the catastrophic disruption threshold (Q*D) of non-differentiated spheres of rock and ice at fixed impact velocity.

The ~520 km diameter asteroid Vesta is the first Dawn mission target (Russell et al., P&SS 2004). It is a riddle not only for the unique survival of its basaltic crust, but also for the existence of a southern-hemispheric crater of diameter ~450 km (Thomas et al., Icarus 1997) and its taxonomic and dynamical connection to the family of V-class asteroids (Binzel & Xu, Science 1993). It also represents an important end-member in the mechanics of complex cratering, given that its giant crater forms in a gravity field ~1/30 that of Earth.

Our focus on large differentiated asteroids addresses four questions: (1) How do the largest craters on such asteroids form; (2) under what conditions can high-velocity impacts remove a significant fraction of the mantle, possibly exposing core materials in the manner proposed for M-class asteroids like Psyche (Davis et al., Icarus 1999); (3) what mechanical and thermodynamical processing occurs in the shock acceleration of this escaping mantle material, in the context of meteorite petrogenesis, and (4) what processing occurs to the surviving target asteroid.

This work is funded by NASA PG&G ``Small Bodies and Planetary Collisions".

The author(s) of this abstract have provided an email address for comments about the abstract: asphaug@pmc.ucsc.edu

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.