The Magnetospheric Plasma–driven Evolution of Satellite Atmospheres

Atmospheric loss induced by an incident plasma, often called atmospheric sputtering, can significantly alter the volatile inventories of solar system bodies. Based on the present atmospheric sputtering rate, the net loss of nitrogen from Titan in the last 4 Gyr was small, consistent with Titan retaining a component of its primordial atmosphere. However, atmospheric sputtering by the magnetospheric plasma ions and by pickup ions, even at present levels, would have caused the loss of a large, residual Titan-like atmosphere from Io and Europa and a significant fraction of such an atmosphere from Ganymede. At Callisto, higher magnetospheric plasma densities would have been required for the loss of such an atmosphere. Since higher plasma densities were probable in earlier epochs, the evolution of the volatile inventories of each of the Galilean satellites has been profoundly affected by the interaction of their atmospheres with the Jovian magnetospheric plasma. Subject headings: planets and satellites: formation — planets and satellites: individual (Callisto, Europa, Ganymede, Io, Titan)