Statistics – Computation
Scientific paper
Oct 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010dps....42.0102r&link_type=abstract
American Astronomical Society, DPS meeting #42, #1.02; Bulletin of the American Astronomical Society, Vol. 42, p.941
Statistics
Computation
Scientific paper
The evolution of the icy satellites is complex and currently poorly understood. Here we combine thermal evolution models with basin relaxation calculations to place tighter constraints on the early history of these bodies.
We have coupled the results of a model for the internal evolution of Iapetus (Robuchon et al, 2010) with a computation of the surface relaxation (Zhong et al, 2003). The evolution of Iapetus is calculated using a 3D model with a temperature-dependent viscosity, while the relaxation is computed with a Maxwell viscoelastic rheology. Our relaxation model was benchmarked against the analytical results given by Melosh (1989) . At each timestep we recompute the effective ice viscosity using the parameters of Goldsby and Kohlstedt (2001). We also investigate the effect of a cutoff in effective viscosity (cf. Dombard and McKinnon, 2006).
Our baseline simulation assumes 72ppb of 26Al, consistent with the results of Robuchon et al. (2010). Bigger basin relax more rapidly than smaller ones, because the inferred thickness of the ice shell of Iapetus exceeds the diameter of even the largest basins considered. Due to the cooling of Iapetus, the younger basins relax less than the older. Our results show a maximum relaxation of less than 20% for the older and bigger basins and less than 5% for the smaller. These results are in good agreement with measurements of basin depth (Schenk and Moore, 2007) assuming that basin formation occurred about 900 Myr after the formation of the Solar System.
By linking models of internal evolution and basin relaxation, we can place tighter constraints on the histories of the Saturnian icy satellites. For instance, our initial results are consistent with basin formation at the time of the Late Heavy Bombardment. A critical observational requirement is the ages of the largest impact basins on the icy satellites.
Nimmo Francis
Roberts Jeffery J.
Robuchon Guillaume
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