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.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

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.

References

  1. 1

    Hunten, D. M., et al. in Saturn (eds Gehrels, T. & Shapley Matthews, M.) 671–759 (Univ. Arizona Press, Tucson, 1984)

    Google Scholar 

  2. 2

    Kunde, V. G. et al. C4H2, HC3N and C2N2 in Titan's atmosphere. Nature 292, 686–688 (1981)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Niemann, H. B. et al. The Gas Chromatograph Mass Spectrometer for the Huygens probe. Space Sci. Rev. 104(1), 553–591 (2002)

    ADS  CAS  Article  Google Scholar 

  4. 4

    Lorenz, R. D., McKay, C. P. & Lunine, J. L. Photochemically driven collapse of Titan's atmosphere. Science 275, 642–644 (1997)

    ADS  CAS  Article  Google Scholar 

  5. 5

    Niemann, H. B. et al. Chemical composition measurements of the atmosphere of Jupiter with the Galileo Probe Mass Spectrometer. Adv. Space Res. 21, 1455–1461 (1998)

    ADS  CAS  Article  PubMed  Google Scholar 

  6. 6

    Lunine, J. I. & Stevenson, D. J. Clathrate and ammonia hydrates at high pressure: Application to the origin of methane on Titan. Icarus 70, 61–77 (1987)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Bar-Nun, A., Kleinfeld, A. I. & Kochavi, E. Trapping of gas mixtures by amorphous ice. Phys. Rev. B 38, 7749–7754 (1988)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Owen, T. & Gautier, D. Touring the Saturn system: The atmospheres of Saturn and Titan. Space Sci. Rev. 104, 347–376 (2002)

    ADS  CAS  Article  Google Scholar 

  9. 9

    Tobie, G., Grasset, O., Lunine, J. I., Mocquet, A. & Sotin, C. Titan's internal structure inferred from a coupled thermal-orbital model. Icarus 175, 496–502 (2005)

    ADS  CAS  Article  Google Scholar 

  10. 10

    Owen, T. & Bar Nun, A. Comets, impacts and atmospheres. Icarus 116, 215–226 (1995)

    ADS  CAS  Article  PubMed  Google Scholar 

  11. 11

    Hersant, F., Gautier, D. & Lunine, J. Enrichment in volatiles in the giant planets of the Solar System. Planet. Space Sci. 52, 623–641 (2004)

    ADS  CAS  Article  Google Scholar 

  12. 12

    Mousis, O., Gautier, D. & Bockelée-Morvan, D. Turbulent model of the Saturn subnebula: Implications for the origin of methane in Titan's atmosphere. Icarus 156, 162–175 (2002)

    ADS  CAS  Article  Google Scholar 

  13. 13

    Atreya, S. K., Donahue, T. M. & Kuhn, W. R. Evolution of a nitrogen atmosphere on Titan. Science 201, 611–613 (1978)

    ADS  CAS  Article  PubMed  Google Scholar 

  14. 14

    Kuramoto, K. & Matsui, T. Formation of a hot proto-atmosphere on the accreting giant icy satellite: Implications for the origin and evolution of Titan, Ganymede, and Callisto. J. Geophys. Res. 99(E10), 21183–21200 (1994)

    ADS  Article  Google Scholar 

  15. 15

    McKay, C. P., Scattergood, T. W., Pollack, J. B., Borucki, W. J. & Van Ghysegahm, H. T. High temperature shock formation of N2 and organics on primordial Titan. Nature 332, 520–522 (1988)

    ADS  CAS  Article  PubMed  Google Scholar 

  16. 16

    Bockelee-Morvan, D., Crovisier, J., Mumma, M. J. & Weaver, H. A. The composition of cometary volatiles in Comets II. (eds Festou, M., Weaver, H. A. & Keller, H. U.) 391–423 (Univ. Arizona Press, Tucson, 2004)

  17. 17

    de Bergh, C., Lutz, B., Owen, T. & Chauville, J. Monodeuterated methane in the outer solar system. III. Its abundance on Titan. Astrophys. J. 311, 501–510 (1986)

    ADS  CAS  Article  Google Scholar 

  18. 18

    Coustenis, A., Bézard, B. & Gautier, D. Titan's atmosphere from Voyager infrared observations: II. The CH3D abundance and D/H ratio from the 900–1,200 cm-1 spectral region. Icarus 82, 67–80 (1989)

    ADS  CAS  Article  Google Scholar 

  19. 19

    Orton, G. et al. The D/H ratio on Titan from ISO and IRSHELL Data 81 (ESA report SP 338, Noordwijk, 1992)

    Google Scholar 

  20. 20

    Coustenis, A. et al. Titan's atmosphere from ISO mid-infrared spectroscopy. Icarus 161, 383–403 (2003)

    ADS  CAS  Article  Google Scholar 

  21. 21

    Meier, R. & Owen, T. Cometary deuterium. Space Sci. Rev. 90, 33–43 (1999)

    ADS  CAS  Article  Google Scholar 

  22. 22

    Flasar, F. M. et al. Titan's atmospheric temperatures, winds, and composition. Science 308, 975–978 (2005)

    ADS  CAS  Article  PubMed  PubMed Central  Google Scholar 

  23. 23

    Kouvaris, L. C. & Flasar, F. M. Phase equilibrium of methane and nitrogen at low temperatures—Application to Titan. Icarus 91, 112–124 (1991)

    ADS  CAS  Article  Google Scholar 

  24. 24

    Sagan, C., Thompson, W. R. & Khare, B. N. Titan: a laboratory for prebiological organic chemistry. Acc. Chem. Res. 25, 286–292 (1992)

    CAS  Article  PubMed  Google Scholar 

  25. 25

    Marten, A., Hidayat, T., Biraud, Y. & Moreno, R. New millimeter heterodyne observations of Titan: Vertical distributions of nitriles HCN, HC3N, CH3CN, and the isotopic ratio 15N/14N in its atmosphere. Icarus 158, 532–544 (2002)

    ADS  CAS  Article  Google Scholar 

  26. 26

    Lunine, J. I., Yung, Y. L. & Lorenz, R. D. On the volatile inventory of Titan from isotopic abundances in nitrogen and methane. Planet. Space Sci. 47, 1291–1303 (1999)

    ADS  CAS  Article  Google Scholar 

  27. 27

    Hidayat, T. et al. Millimeter and submillimeter heterodyne observations of Titan: Retrieval of the vertical profile of HCN and the 12C/13C ratio. Icarus 126, 170–182 (1997)

    ADS  CAS  Article  Google Scholar 

  28. 28

    Owen, T., Mahaffy, P. R., Niemann, H. B., Atreya, S. K. & Wong, M. Protosolar nitrogen. Astrophys. J. 553, L77–L79 (2001)

    ADS  CAS  Article  Google Scholar 

  29. 29

    Owen, T., Biver, N., Marten, A., Matthews, H. & Meier, R. Saturn VI (Titan). (ed. Green, D. W. E.) IAU Circ. 7306, 3, (1999)

    Google Scholar 

  30. 30

    Wong, A.-S., Morgan, C. G., Yung, Y. L. & Owen, T. Evolution of CO on Titan. Icarus 155, 382–392 (2002)

    ADS  CAS  Article  Google Scholar 

  31. 31

    Strobel, D. F. The photochemistry in the atmosphere of Titan. Icarus 21, 466–470 (1974)

    ADS  CAS  Article  Google Scholar 

  32. 32

    Yung, Y. L., Allen, M. & Pinto, J. P. Photochemistry of the atmosphere of Titan—Comparison between model and observations. Astrophys. J. Suppl. Ser. 55, 465–506 (1984)

    ADS  CAS  Article  Google Scholar 

  33. 33

    Wilson, E. H. & Atreya, S. K. Current state of modelling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. J. Geophys. Res. 109, E06002, doi:10.1029/2003JE002181 (2004)

    ADS  Article  Google Scholar 

  34. 34

    Boetius, A. Lost city life. Science 307, 1420 (2005)

    CAS  Article  PubMed  Google Scholar 

  35. 35

    Kelley, D. S. et al. A serpentinite-hosted ecosystem: the lost city hydrothermal field. Science 307, 1428–1434 (2005)

    ADS  CAS  Article  PubMed  Google Scholar 

  36. 36

    Chiodini, G. Carbon dioxide Earth degassing and seismogenesis in central and southern Italy. Geophys. Res. Lett. 31, L07615 (2004)

    ADS  Article  Google Scholar 

  37. 37

    Foustouskos, D., Seyfried, W. E. & Dionysis, I. Hydrocarbons in hydrothermal vent fluids: the role of chromium-bearing catalysts. Science 304, 1002–1005 (2004)

    ADS  Article  Google Scholar 

  38. 38

    Hersant, F. G., Gautier, D. & Lunine, J. Enrichment in volatiles in the giant planets in the Solar System. Planet. Space Sci. 52, 623–641 (2004)

    ADS  CAS  Article  Google Scholar 

  39. 39

    Mousis, O., Gautier, D. & Bockelee-Morvan, D. An evolutionary turbulent model of Saturn's subnebula: implications for the origin of the atmosphere of Titan. Icarus 156, 162–175 (2002)

    ADS  CAS  Article  Google Scholar 

  40. 40

    Holland, H. The Chemical Evolution of the Atmosphere and Oceans 39 (Princeton Univ. Press, Princeton, 1984)

    Google Scholar 

  41. 41

    Owen, T. C. The composition and origin of Titan's atmosphere. Planet. Space Sci. 30, 833–838 (1982)

    ADS  CAS  Article  Google Scholar 

  42. 42

    Engel, S., Lunine, J. I. & Norton, D. L. Silicate interactions with ammonia-water fluids on early Titan. J. Geophys. Res. 99, 3745–3752 (1994)

    ADS  CAS  Article  Google Scholar 

  43. 43

    Elachi, C. et al. Cassini RADAR's first views of the surface of Titan. Science 308, 970–974 (2005)

    ADS  CAS  Article  Google Scholar 

  44. 44

    Sotin, C. et al. Release of volatiles from a possible cryovolcano from near-infrared imaging of Titan. Nature 435, 786–789 (2005)

    ADS  CAS  Article  PubMed  PubMed Central  Google Scholar 

  45. 45

    Lebonnois, S. et al. Seasonal variations of Titan's atmospheric composition. Icarus 152, 384–406 (2001)

    ADS  CAS  Article  Google Scholar 

  46. 46

    Waite, J. H. et al. Ion neutral mass spectrometer results from the first flyby of Titan. Science 308, 982–986 (2005)

    ADS  CAS  Article  Google Scholar 

  47. 47

    Wilson, E. H. & Atreya, S. K. Chemical sources of haze formation in Titan's atmosphere. Planet. Space Sci. 51, 1017–1033 (2003)

    ADS  CAS  Article  Google Scholar 

  48. 48

    Israel, G. et al. Huygens Probe Aerosol Collector Pyrolyser Experiment. Space Sci. Rev. 104(1), 433–468 (2002)

    ADS  CAS  Article  Google Scholar 

Download references

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.

Author information

Affiliations

Authors

Corresponding author

Correspondence to H. B. Niemann.

Ethics declarations

Competing interests

Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

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

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.