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L.S. Bruesch, E. Asphaug (UC Santa Cruz)
Disrupted terrains that form as a consequence of giant impacts may help constrain the internal structures of planets, asteroids, comets and satellites. As shock waves and powerful seismic stress waves propagate through a body, they interact with the internal structure in ways that may leave a characteristic impression upon the surface. Variations in peak surface velocity and tensile stress, related to landform degradation and surface rupture, may be controlled by variations in core size, shape and density. Caloris Basin on Mercury and Imbrium Basin on the moon have disturbed terrain at their antipodes, where focusing is most intense for an approximately symmetric spheroid. Although the icy Saturnian satellites Tethys, Mimas and Rhea possess giant impact structures, it is not clear whether these structures have correlated disrupted terrains at their antipodes.
In anticipation of high-resolution imagery from Cassini, we investigated antipodal damage during giant impacts using a 3D SPH impact model. We first investigated giant impacts into a fiducial 1000-km diameter icy satellite with a variety of core properties. We then modeled the formation of the impact structures Odysseus (on Tethys), Herschel (on Mimas) and Tirawa (on Rhea), using image-derived shapes for each satellite (triaxial for Tethys and Mimas and spherical for Rhea). We performed a matrix of simulations with various core radii and densities and impact angles. Our initial results indicate that surface rupture and degradation can vary significantly with core geometry for a given impact angle and that this method may therefore be combined with future high-resolution imagery to constrain satellite interior structure. More detailed results will be reported at the meeting.
This work was supported by NASA’s Planetary Geology and Geophysics Program Grant #NAG5-8914.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.