The librations, shape, and icy shell of Europa

摘要: Europa, the smallest of Galilean satellites, has a young icy surface and most likely contains an internal ocean. The primary objective possible future missions to Europa is unambiguous detection characterization subsurface thickness overlying shell provides important information on thermal evolution satellite interaction between ocean surface, latter being fundamental for astrobiology. However, not well known, estimates range from several hundred meters some ten kilometers. Here, we investigate use libration (rotation variation) observations study interior structure in particular its shell. A dynamical model developed, which includes gravitational coupling heavy solid interior. amplitude main signal at 3.55 days (the orbital period) shown depend Europa's shape structure. Models are constructed equatorial flattening layers, key parameters libration, calculated by assuming that hydrostatic equilibrium. flattened assumed be due rotation permanent tides, extend classical Radau equation rotationally bodies include also tidal deformation. We show presence increases about 10%, depending mainly Therefore, offer possibility estimation