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The abundances of constituents of Titan's atmosphere from the GCMS instrument on the Huygens probe

Nature volume 438, pages 779–784 (2005)Cite this article

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.

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Figure 1: Sample-averaged mass spectra, showing ion count rates per second versus mass per unit charge ( m/z ) from direct atmospheric sampling.
Figure 2: The mole fraction of methane to nitrogen in the Titan atmosphere is plotted versus altitude.
Figure 3: Pulse count rates of nitrogen and methane are shown versus time.

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Acknowledgements

This paper is dedicated to the memory of T. Donahue, who contributed to the planning and development of the GCMS, and died before the Huygens probe encountered Titan. We acknowledge the HASI team, who provided the atmospheric pressure–temperature–altitude data to the GCMS team. We thank F. M. Flasar, R. H. Brown and C. Sotin for providing preprints of their Cassini papers. We also thank G. Tobie for information on the story of clathrate hydrates within Titan, F. Hersant for discussions on enrichments by clathration in giant planets and D. Strobel for his discussions of atmospheric loss. The contributions of personnel at the NASA Goddard Space Flight Center, the University of Michigan, the Ohio State University and the University of Paris are acknowledged. We thank the personnel at the European Space Research and Technology Centre (ESTEC) and the European Space Operations Centre (ESOC) for their technical support and guidance during this mission. We acknowledge NASA, ESA and CNES for support of the mission.

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Authors and Affiliations

  1. National Aeronautics and Space Administration, Maryland, 20771, Greenbelt, USA

    H. B. Niemann, J. E. Demick, J. A. Haberman, D. N. Harpold, W. T. Kasprzak, M. Paulkovich, E. Raaen & S. H. Way

  2. University of Michigan, Michigan, 48109-2143, Ann Arbor, USA

    S. K. Atreya & G. R. Carignan

  3. Institute for Meteorology and Geophysics, University of Graz, A-8010, Graz, Austria

    S. J. Bauer

  4. LESIA, Observatoire de Paris-Meudon, F-92195, Meudon Cedex, France

    D. Gautier

  5. Lunar and Planetary Laboratory, University of Arizona, Arizona, 85716, Tucson, USA

    D. M. Hunten & J. I. Lunine

  6. Service d'Aéronomie du CNRS, F-91371 Verrières le Buisson Cedex, France

    G. Israel

  7. University of Alabama, CMC, 817 22nd Street South, Alabama, 35205, Birmingham, USA

    R. L. Frost

  8. University of Hawaii, Hawaii, 96822, Honolulu, USA

    T. C. Owen

  9. Laboratoire Interuniversitaire des Systèmes Atmosphériques, Université Paris 12 et Paris 7, Avenue du Général de Gaulle, F-94010, Creteil Cedex, France

    F. Raulin

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Correspondence to H. B. Niemann.

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Niemann, H., Atreya, S., Bauer, S. et al. The abundances of constituents of Titan's atmosphere from the GCMS instrument on the Huygens probe. Nature 438, 779–784 (2005). https://doi.org/10.1038/nature04122

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