title: The process of tholin formation in Titan's upper atmosphere.
abstract: Titan's lower atmosphere has long been known to harbor organic aerosols (tholins) presumed to have been formed from simple molecules, such as methane and nitrogen (CH4 and N2). Up to now, it has been assumed that tholins were formed at altitudes of several hundred kilometers by processes as yet unobserved. Using measurements from a combination of mass/charge and energy/charge spectrometers on the Cassini spacecraft, we have obtained evidence for tholin formation at high altitudes (approximately 1000 kilometers) in Titan's atmosphere. The observed chemical mix strongly implies a series of chemical reactions and physical processes that lead from simple molecules (CH4 and N2) to larger, more complex molecules (80 to 350 daltons) to negatively charged massive molecules (approximately 8000 daltons), which we identify as tholins. That the process involves massive negatively charged molecules and aerosols is completely unexpected.
authors.affiliation: Space Science and Engineering Division, Southwest Research Institute (SWRI), 6220 Culebra Road, San Antonio, TX 78238, USA. hwaite@swri.edu
authors.forename: J H
authors.initials: JH
authors.lastname: Waite
authors.forename: D T
authors.initials: DT
authors.lastname: Young
authors.forename: T E
authors.initials: TE
authors.lastname: Cravens
authors.forename: A J
authors.initials: AJ
authors.lastname: Coates
authors.forename: F J
authors.initials: FJ
authors.lastname: Crary
authors.forename: B
authors.initials: B
authors.lastname: Magee
authors.forename: J
authors.initials: J
authors.lastname: Westlake
mesh_terms: D000336:Aerosols; D001272:Atmosphere; D001554:Benzene; D005118:Extraterrestrial Environment; D006838:Hydrocarbons; D007477:Ions; D008970:Molecular Weight; D009570:Nitriles; D010777:Photochemistry; D018539:Saturn; D018531:Spacecraft; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D000336:Aerosols; D006838:Hydrocarbons; D007477:Ions; D009570:Nitriles; D001554:Benzene