Exploring the Moons of Jupiter and Saturn with a magnetometer

Résumé: Magnetic signatures acquired by spacecraft passing near Jupiter's and Saturn's large moons provide indirect evidence of many fundamental properties of these exotic bodies. A deep understanding of the physics of the interaction between the moons and the flowing plasma of the magnetospheres within which they are embedded is essential to a meaningful interpretation of the measurements. Magnetic signatures can distinguish low conductance bodies from high conductance bodies. High frequency magnetic perturbations can show that newly ionized material is being introduced into the background plasma, thereby providing insight into trace materials on the moon's surface or in its atmosphere. The presence of induced fields can constrain properties of the moon's sub-surface layers. The presence of a self-generated internal field, as at Ganymede, gives insight into the structure of the deep interior, but refined characterization of the internal field requires a full understanding of the externally generated contributions to the measured field. Perturbations associated with field-aligned currents can reveal the presence of an ionized region surrounding a moon. Indeed, it was the identification of subtle aspects of the magnetic symmetry that first suggested the existence of vapor jets at Enceladus even before the plume was imaged by Cassini instrumentation. -------------------------------------------------------------------------------- Séminaires généraux de l'Institut de Physique du Globe de Paris --------------------------------------------------------------------------------