Astronomy and Astrophysics – Astrophysics
Scientific paper
Jul 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007sf2a.conf..118r&link_type=abstract
SF2A-2007: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics held in Grenoble, France, July
Astronomy and Astrophysics
Astrophysics
Scientific paper
The detection of an induced magnetic field in the vicinity of the Galilean satellite Europa by the Galileo mission suggests the existence of a subsurface ocean of liquid water. The thickness of the overlying ice shell provides important information on the thermal evolution of the satellite and determines the interaction between the ocean and the surface, which is fundamental for question of habitability. However, the thickness is not well known and estimates vary between several hundred of meters and tens of kilometers. Here, we investigate the use of libration observations to study the ice shell thickness and we isolate the signature of the relevant geophysical parameters. The amplitude of the libration in longitude of 3.55 days (the orbital period) depends on both the gravitational torque exerted by Jupiter on Europa and internal coupling. We investigate different scenario of internal structure of Europa and the libration of the outer ice shell is significantly different with an ocean. We include gravitational coupling between the ice shell and the solid interior, which contains most of EuropaÕs mass. We show that the presence of an ocean can increase the amplitude of libration by about 7% to 25% (147 ± 5 meters) than the purely rigid case (amplitude about 134 meters) depending mainly on the ice shell thickness. For small thickness, the amplitude of libration increases strongly due to a resonance with a normal mode. We present the impact of other parameters such as densities and internal flattenings on libration amplitude.
Hoolst Tim Van
Karatekin Ö.
Rambaux Nicolas
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