The Escape Probability of Some Ions from Mars and Titan Ionospheres

The Kinetic Energy Release (KER) for various ionic species coming from two-body dissociations reactions, induced by double photoionization of CO2, C2H2 and N2O neutral precursors of interest in planetary atmospheres, are reported. The KER distributions as a function of the VUV photon energy in the range of 30-65 eV are extracted from the coincidences spectra obtained by using tunable synchrotron radiation and electron-ion-ion coincidences coupled with ion imaging techniques. This experimental method, coupled with a computational analysis of the data based on a Monte Carlo trajectoriy simulation, allows to discuss about the probability for some ionic species to escape the upper atmosphere of Mars and Titan. In fact, the KER measured for H+, C+, CH+, CH2+, N+, O+ and CO+ fragment ions are ranging between 1.0 and 6.0 eV, and these translational energy contents are large enough to allow these ionic species in participating in the atmospheric escape from Mars and Titan into space.