HR: 0800h
AN: P11B-0114    [Abstracts]
TI: Implications of Europa's broadband seismic response calculated from physically consistent models
AU: Manga, M
EM: manga@seismo.berkeley.edu
AF: UC Berkeley, Dept. of Earth and Planetary Science, 307 McCone Hall, Berkeley, CA 94720 United States
AU: * Panning, M P
EM: mpanning@seismo.berkeley.edu
AF: Berkeley Seismological Lab, 215 McCone Hall, Berkeley, CA 94720 United States
AU: Lekic, V
EM: lekic@seismo.berkeley.edu
AF: Berkeley Seismological Lab, 215 McCone Hall, Berkeley, CA 94720 United States
AU: Cammarano, F
EM: fabio@seismo.berkeley.edu
AF: Berkeley Seismological Lab, 215 McCone Hall, Berkeley, CA 94720 United States
AU: Romanowicz, B A
EM: barbara@seismo.berkeley.edu
AF: Berkeley Seismological Lab, 215 McCone Hall, Berkeley, CA 94720 United States
AB: Measurements of the seismic response of Europa remotely from an orbiter or using a lander can greatly expand our knowledge of the internal structure and thermal evolution and therefore of the potential for life. We explore a range of reasonable physical models of Europan 1D structure to determine the types of seismic signals relevant for discriminating between the various models. We calculate a range of thermodynamically consistent models constrained by the mass and moment of inertia. We start with either pyrolitic or chondritic mantle composition, and use a range of thermal structures consistent with the surface temperature and the presence of a liquid water ocean. These range from hot, convective mantle models where internal heating from tidal dissipation is important at all depths to relatively cold mantle with much less dissipation. The core can be either pure solid iron or liquid with iron and sulfur at eutectic concentrations. These models are used to calculate free oscillation catalogs that define the broadband seismic response for periods less than 10 seconds to many 1000's of seconds. Surface waves with periods between 10 and 100 seconds, which may be measurable from orbit, can be used to discriminate between different thicknesses of the ice shell, an important result for estimates of the availability of liquid water for life as well as for any potential lander mission. Thin shells with thicknesses of 5 km or less produce very dispersive surface wave trains with large amplitudes of displacement up to a few cm at distances of 400 km for a reasonable M_W 5 event, while thicker ice shells have somewhat lower amplitude and more impulsive surface waves. The lower frequency oscillations allow determination of the deep structure, including core radius and light element content as well as the attenuation structure, which is important to understand the thermal evolution and current heat budget of the icy moon. The presence of a liquid ocean layer also allows for very long-period modes which may allow strong tidal coupling with Io which can be another important input for the heat budget.
DE: 3909 Elasticity and anelasticity
DE: 5430 Interiors (8147)
DE: 6218 Jovian satellites
DE: 7255 Surface waves and free oscillations
SC: Planetary Sciences [P]
MN: Fall Meeting 2005