title: The abundances of constituents of Titan's atmosphere from the GCMS instrument on the Huygens probe.
abstract: Saturn's largest moon, Titan, remains an enigma, explored only by remote sensing from Earth, and by the Voyager and Cassini spacecraft. The most puzzling aspects include the origin of the molecular nitrogen and methane in its atmosphere, and the mechanism(s) by which methane is maintained in the face of rapid destruction by photolysis. The Huygens probe, launched from the Cassini spacecraft, has made the first direct observations of the satellite's surface and lower atmosphere. Here we report direct atmospheric measurements from the Gas Chromatograph Mass Spectrometer (GCMS), including altitude profiles of the constituents, isotopic ratios and trace species (including organic compounds). The primary constituents were confirmed to be nitrogen and methane. Noble gases other than argon were not detected. The argon includes primordial 36Ar, and the radiogenic isotope 40Ar, providing an important constraint on the outgassing history of Titan. Trace organic species, including cyanogen and ethane, were found in surface measurements.
authors.affiliation: National Aeronautics and Space Administration, Greenbelt, Maryland 20771, USA. Hasso.B.Niemann@nasa.gov
authors.forename: H B
authors.initials: HB
authors.lastname: Niemann
authors.forename: S K
authors.initials: SK
authors.lastname: Atreya
authors.forename: S J
authors.initials: SJ
authors.lastname: Bauer
authors.forename: G R
authors.initials: GR
authors.lastname: Carignan
authors.forename: J E
authors.initials: JE
authors.lastname: Demick
authors.forename: R L
authors.initials: RL
authors.lastname: Frost
authors.forename: D
authors.initials: D
authors.lastname: Gautier
authors.forename: J A
authors.initials: JA
authors.lastname: Haberman
authors.forename: D N
authors.initials: DN
authors.lastname: Harpold
authors.forename: D M
authors.initials: DM
authors.lastname: Hunten
authors.forename: G
authors.initials: G
authors.lastname: Israel
authors.forename: J I
authors.initials: JI
authors.lastname: Lunine
authors.forename: W T
authors.initials: WT
authors.lastname: Kasprzak
authors.forename: T C
authors.initials: TC
authors.lastname: Owen
authors.forename: M
authors.initials: M
authors.lastname: Paulkovich
authors.forename: F
authors.initials: F
authors.lastname: Raulin
authors.forename: E
authors.initials: E
authors.lastname: Raaen
authors.forename: S H
authors.initials: SH
authors.lastname: Way
mesh_terms: D001128:Argon / Q000032:analysis; D001272:Atmosphere / Q000737:chemistry*; D002244:Carbon / Q000032:analysis / Q000737:chemistry; D005118:Extraterrestrial Environment / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000295:instrumentation*; D007554:Isotopes / Q000032:analysis; D008697:Methane / Q000032:analysis / Q000737:chemistry; D009584:Nitrogen / Q000032:analysis / Q000737:chemistry; D013026:Space Flight / Q000295:instrumentation
chemical_list: D007554:Isotopes; D001128:Argon; D002244:Carbon; D009584:Nitrogen; D008697:Methane