INMS quarterly report: May-July, 2005 Science highlights –In situ determination of the ionospheric composition of Titan … the hydrocarbon and nitrile complexity of the mass spectrum is unprecedented in a planetary environment. –In situ determination of the atmosphere of Enceladus much beyond anticipation - water 65%, molecular hydrogen 20%, carbon monoxide or molecular nitrogen 8%, carbon dioxide 2.5%, and perhaps traces of methane and ammonia.

Complex Carbon Nitrile Chemistry The neutral composition at 1200 km in addition to the primary constituents N 2, CH 4, and H 2 includes a host of hydrocarbons: C 2 H 2, C 2 H 2, C 2 H 6,C 3 H 4, C 3 H 8, C 4 H 2, HCN, HC 3 N, C 2 N 2, and C 6 H 6. ==> TITAN”S UPPER ATMOSPHERE IS A KEY SOURCE of CARBON NITRILE COMPOUNDS Correspondingly, the ionospheric composition has a complex hydrocarbon and nitrile chemistry that includes almost all possible hydrocarbon species through C7. N2N2 CH 4 H2H2 C6H6C6H6 C3H4C3H4 C4H2C4H2 C7s C6s C5s C4s C3s HCNH

Enceladus Atmosphere As Viewed From INMS H 2 O Altitude Variation variation is 1/r surface density from extrapolation is 1.56x10 6 some evidence for localized atmospheric structure near closest approach Composition

INMS quarterly report: May-July, 2005 Science plans –Upcoming INMS measurements of Titan’s atmosphere on T7 will continue to investigate the variability of Titan’s atmosphere in hopes of setting more definitive guidelines for the safe altitude of future Titan flybys. –Excellent INMS measurements of the atmosphere from the recent flyby of Enceladus suggest that a close flyby (~25 km) planned for orbit 061 with INMS in the ram direction will allow a definitive determination of the atmospheric composition including a measurement of the D/H and 14 N/ 15 N ratios.

INMS quarterly report: May-July, 2005 Talks given by the INMS team 1.EGS invited talk Wayne Kasprzak 2.Spring AGU, New Orleans –Titan atmospheric structure Roger Yelle –Titan ionospheric composition Tom Cravens –The ring ionosphere Janet Luhmann –Titan ENA source modeling Steve Ledvina 3.Crete Titan workshop –Titan atmospheric composition Hunter Waite –Titan atmospheric structure Roger Yelle 4.AOGS invited talk, Singapore of INMS results Ralph McNutt

INMS quarterly report: May-July, 2005 Papers submitted by the INMS 1.INMS results from first Titan flyby published in May 13th special issue of Science, Waite et al., Titan atmospheric structure submitted to JGR in June, Yelle et al., Titan ionospheric structure in press in GRL, Cravens et al., Titan atmospheric composition in preparation for JGR, De La Haye et al., Titan ionospheric composition in preparation for JGR, Cravens et al., The ring ionosphere in preparation for Icarus, Luhmann et al., 2005