DDA 36th Meeting, 10-14 April 2005
Session 15 Gas and Dissipative Dynamics
Oral, Thursday, April 14, 2005, 9:35am-11:35pm

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[15.02] Kinds of Planetary Collisions

E. Asphaug, C. Agnor (UCSC)

Terrestrial planet formation, and core accretion in general, ends with a series of giant impacts involving planet-sized bodies. In many accretion simulations these giant impacts are modeled as perfectly inelastic mergers. The truth however is that of only half of collisions between rocky planets (for the velocity regime vesc = vinf) result in net mass accretion, with the other half resulting in episodes that have, to date, received very little treatment and may have significant implications for meteoritics, asteroid genesis, and planet formation.

We discuss the wide range of giant impacts from direct impacts, to grazing encounters, where atmosphere and outer mantle can be lost, to events where the smaller of the two encountering bodies is shredded into a "string of pearls" -- planets ranging in composition from pure mantle to iron-enriched. Thermophysics of pressure unloading is significant in such events. Tides and shock stresses both play intimate roles in such events, and the impactor -- which emerges from about half of collisions -- is most severely altered.

This work was supported by the NASA Planetary Geology and Geophysics Program, "Small Bodies and Planetary Collisions"

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

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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.