The Atmospheres of Titan and Enceladus as Revealed by the Cassini Mission
and
A brief introduction to the University of Kansas Graduate Program in Physics
By T. E. Cravens
Department of Physics, University of Kansas
The Cassini-Huygens spacecraft was launched by NASA in October 1997 on a Titan- Centaur vehicle and then, after firing its main engines and passing through the ringplane, went into orbit around Saturn in July 2004. The Huygens probe landed on Titan's surface in January 2005 and the Cassini Orbiter with its many instruments continued to study the Saturn system with its many satellites and its rings. This colloquium will emphasize what has been learned about the atmospheres and plasma environments of Enceladus and Titan. Particular emphasis will be given to composition and density data obtained by the Ion and Neutral Mass Spectrometer (INMS). Titan is the largest satellite of Saturn and has a dense atmospheric whose main constituents are nitrogen and methane. Solar and x-ray radiation, as well as energetic plasma from Saturn's magnetosphere, interact with the upper atmosphere producing an ionosphere at Titan. The highly coupled ionosphere and upper atmosphere system mediates the interaction between Titan and the external environment. Enceladus is a much smaller moon -- only 504 km across. The surface is icy and crevices in the southern hemisphere act as the source of a water vapor plume, or geyser. The INMS detected a plume atmosphere consisting mainly of water but also with some carbon dioxide, carbon monoxide, and nitrogen gases. The INMS and other Cassini instruments also observed a plasma environment, or ionosphere, associated with the plume. The plume ionosphere undergoes a complex interaction with Saturn's magnetosphere.