HR: 0800h
AN: P21B-0539 [Abstracts]
TI: The effect of near-surface heating on the underlying convection pattern with application to Enceladus
AU: * Roberts, J H
EM: jhr@ucsc.edu
AF: Dept. of Earth and Planetary Sciences, University of California, Santa Cruz, 1156 High
Street, Santa Cruz, CA 95064-1077, United States
AU: Nimmo, F
EM: fnimmo@es.ucsc.edu
AF: Dept. of Earth and Planetary Sciences, University of California, Santa Cruz, 1156 High
Street, Santa Cruz, CA 95064-1077, United States
AB:
Rapid strike-slip motion is predicted to be a consequence of diurnal tidal stresses in most satellites of the outer
solar system with short orbital timescales [1]. Such motion can lead to near-surface heating through friction or
viscous dissipation [2]. Here we discuss the effect of near-surface shear heating on convection in the underlying
ice shells of icy satellites [3], with a focus on Enceladus and a possible origin of the south polar thermal anomaly
[4].
We present models of convection in spherical ice shells including both spatially variable volumetric tidal heating
[5] and regional shear heating localized in the top 5 km at either the pole or the equator. We observe that the
presence of the near-surface heating strongly controls the convective pattern, increasing the wavelength, and
promoting the formation of a hot upwelling beneath the shear zone. Our results suggest that localized near-
surface heating may result in a degree-1 convective planform in an ice shell of a thickness that may be
appropriate for a differentiated Enceladus (d < 0.36 Rsat).
The near-surface heating and convection pattern will produce a localized heat flow anomaly. The upwelling
beneath the shear zone also produces a few hundred meters of long-wavelength dynamic topography. The
ℓ=2 component of the topography may cause reorientation of the satellite [6].
[1] Hoppa, G., B. R. Tufts, R. Greenberg, and P. Geissler, Icarus, 141, 287-298, 1999. [2] Nimmo, F., E.
Gaidos, JGR, 107, 5021, 2002. [3] Han, L., A. P. Showman, LPSC XXXVIII, #2277, 2007. [4] Spencer,
J. R., et al., Science, 311, 1401-1405. [5] Tobie, G., A. Mocquet, C. Sotin, Icarus, 177 534-549. [6]
Nimmo, F., R. T. Pappalardo, Nature, 441, 614-616.
DE: 5418 Heat flow
DE: 5430 Interiors (8147)
DE: 5450 Orbital and rotational dynamics (1221)
DE: 5475 Tectonics (8149)
DE: 6280 Saturnian satellites
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting