Mass composition of the escaping plasma at Mars
Coates, A. J.; Kallio, E.; Fedorov, A.; Budnik, E.; Säles, T.; Schmidt, W.; Koskinen, H.; Riihelä, P.; Barabash, S.; Lundin, R.; Holmström, M.; Gunell, H.; Futaana, Y.; Andersson, H.; Yamauchi, M.; Grigoriev, A.; Sauvaud, J. -A.; Thocaven, J. -J.; Winningham, J. D.; Frahm, R. A.; Sharber, J. R.; Linder, D. R.; Kataria, D. O.; Kozyra, J.; Roelof, E.; Williams, D.; Livi, S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter, M.; McKenna-Lawler, S.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.; Krupp, N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.; Nilsson, H.; Luhmann, J.; Carlsson, E.; Scherrer, J.
Sweden, France, United States, United Kingdom, Finland, Ireland, Italy, Switzerland, Germany, Japan
Abstract
Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO +2/O + and O +2/O +. The following ratios averaged over all events and energies were identified: CO +2/O + = 0.2 and O +2/O + = 0.9. The values measured are significantly higher, by a factor of 10 for O +2/O +, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O +, followed by O +2 and CO +2. We estimate the loss of CO +2 to be 4.0×10s(0.29 kgs) by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.