Simulation of Atmospheric/Ionospheric Escape from Unmagnetized Bodies

This paper discusses our simulations of ion escape from Mars and Titan. This issue of ion escape has become a topic of major interest with current and future acquisition of ion data from Titan and it's plasma torus, and the issue of water loss from Mars. The simulation tool used for this research is a 3-D spherical hybrid particle code. This code and it's Cartesian predecessor HALFSHEL, have been used for years to study these bodies. However, in the last year substantial changes have been made to the chemistry packages with the code as well as adding ion-neutral and ion-ion drag to the formulation. These additions to the simulations coupled with the higher radial resolution afforded by using spherical coordinates permit higher fidelity simulations of these bodies. The results presented will be of the loss rates found for differing ion species that compose the ionosphere of Mars and Titan.