Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Episodic outgassing as the origin of atmospheric methane on Titan

Nature volume 440, pages 61–64 (2006)Cite this article

Abstract

Saturn's largest satellite, Titan, has a massive nitrogen atmosphere containing up to 5 per cent methane near its surface. Photochemistry in the stratosphere would remove the present-day atmospheric methane in a few tens of millions of years1. Before the Cassini-Huygens mission arrived at Saturn, widespread liquid methane or mixed hydrocarbon seas hundreds of metres in thickness were proposed as reservoirs from which methane could be resupplied to the atmosphere over geologic time2. Titan fly-by observations3,4,5 and ground-based observations6 rule out the presence of extensive bodies of liquid hydrocarbons at present, which means that methane must be derived from another source over Titan's history. Here we show that episodic outgassing of methane stored as clathrate hydrates within an icy shell above an ammonia-enriched water ocean is the most likely explanation for Titan's atmospheric methane. The other possible explanations all fail because they cannot explain the absence of surface liquid reservoirs and/or the low dissipative state of the interior. On the basis of our models, we predict that future fly-bys should reveal the existence of both a subsurface water ocean and a rocky core, and should detect more cryovolcanic edifices.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 2: The evolution of the interior and the outgassing rate of methane over Titan's history.
Figure 1: Global heat power provided by the rocky core.
Figure 3: Thickness of the available methane clathrate reservoir when the final episode initiates.

Similar content being viewed by others

References

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

    Article  ADS  CAS  Google Scholar 

  2. Lunine, J. I., Stevenson, D. J. & Yung, Y. L. Ethane ocean on Titan. Science 222, 1229–1230 (1983)

    Article  ADS  CAS  Google Scholar 

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

    Article  ADS  CAS  Google Scholar 

  4. Elachi, C. et al. Cassini radar views the surface of Titan. Science 308, 970–974 (2005)

    Article  ADS  CAS  Google Scholar 

  5. Porco, C. et al. Imaging of Titan from the Cassini spacecraft. Nature 434, 159–168 (2005)

    Article  ADS  CAS  Google Scholar 

  6. West, R. A., Brown, M. E., Salinas, S. V., Bouchez, A. H. & Roe, H. G. No oceans on Titan from the absence of a near-infrared specular reflection. Nature 436, 670–672 (2005)

    Article  ADS  CAS  Google Scholar 

  7. Stevenson, D. J. in Proceedings Symposium on Titan, Toulouse, France, 9–12 September 1991 29–33 (European Space Agency, Noordwijk, The Netherlands, 1992)

    Google Scholar 

  8. Grasset, O., Sotin, C. & Deschamps, F. On the internal structure and dynamics of Titan. Planet. Space Sci. 48, 617–636 (2000)

    Article  ADS  CAS  Google Scholar 

  9. Owen, T. On the origin of Titan's atmosphere. Planet. Space Sci. 48, 747–752 (2000)

    Article  ADS  CAS  Google Scholar 

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

    Article  ADS  CAS  Google Scholar 

  11. Niemann, H. et al. The abundances of constituents of Titan's atmosphere from the GCMS instrument on the Huygens probe. Nature 438, 779–784 (2005)

    Article  ADS  CAS  Google Scholar 

  12. 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)

    Article  ADS  CAS  Google Scholar 

  13. 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, 21183–21200 (1994)

    Article  ADS  Google Scholar 

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

    Article  ADS  CAS  Google Scholar 

  15. Lowell, R. P. & Rona, P. A. Seafloor hydrothermal systems driven by the serpentinization of peridotite. Geophys. Res. Lett. 29, 1531, doi 10.1029/2001GL014411 (2002)

    Article  ADS  Google Scholar 

  16. Loveday, J. S. et al. Stable methane hydrate above 2 GPa and the source of Titan's atmospheric methane. Nature 410, 661–663 (2001)

    Article  ADS  CAS  Google Scholar 

  17. Sloan, E. D. Clathrates Hydrates of Natural Gases 2nd edn (Marcel Dekker, New York, 1998)

    Google Scholar 

  18. Grasset, O. & Pargamin, J. The ammonia water system at high pressures: implications for the methane of Titan. Planet. Space Sci. 53, 371–384 (2005)

    Article  ADS  CAS  Google Scholar 

  19. 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)

    Article  ADS  CAS  Google Scholar 

  20. Sohl, F., Hussmann, H., Schwentker, B., Spohn, T. & Lorenz, R. D. Interior structure models and tidal Love numbers of Titan. J. Geophys. Res. 108, 5130, doi 10.1029/2003JE002044 (2003)

    Article  Google Scholar 

  21. Durham, W. B., Kirby, S. H., Stern, L. A. & Zhang, W. The strength and rheology of methane clathrate hydrate. J. Geophys. Res. 108, 2182, doi:10.1029/2002JB001872 (2003)

    ADS  Google Scholar 

  22. Sotin, C., Head, J. W. & Tobie, G. Europa: tidal heating of upwelling thermal plumes and the origin of lenticulae and chaos melting. Geophys. Res. Lett. 29, 1233, doi:10.1029/2001GL013844 (2002)

    Article  ADS  Google Scholar 

  23. Tomasko, M. G. et al. Rain, winds and haze during the Huygens probe's descent to Titan's surface. Nature 438, 765–778 (2005)

    Article  ADS  CAS  Google Scholar 

  24. 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)

    Article  ADS  CAS  Google Scholar 

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

    Article  ADS  CAS  Google Scholar 

  26. Dyadin, Y. A., Aladko, E. Y. & Larionov, E. G. Decomposition of methane hydrates up to 15 kbar. Mendeleev Commun. 7, 34–35 (1997)

    Article  Google Scholar 

  27. Dyadin, Y. A., Larionov, E. G., Mirinski, D. S., Mikina, T. V. & Starostina, L. I. Clathrate formation in the Ar–H2O system under pressures up to 15000 bar. Mendeleev Commun. 7, 32–34 (1997)

    Article  Google Scholar 

  28. Castillo, J., Rappaport, J., Moquet, A. & Sotin, C. Clues on Titan's internal structure from Cassini-Huygens mission. Lunar Planet. Sci. (LPI contribution no. 1109) 33, 1989 (2002)

    ADS  Google Scholar 

  29. Rappaport, N., Bertotti, B., Giamperi, G. & Anderson, J. D. Doppler measurements of the quadrupole moments of Titan. Icarus 126, 313–323 (1997)

    Article  ADS  CAS  Google Scholar 

  30. Lorenz, R., Mckay, C. P. & Lunine, J. I. Photochemical collapse of Titan's atmosphere. Science 275, 642–646 (1997)

    Article  ADS  CAS  Google Scholar 

Download references

Acknowledgements

The first author benefits from post-doctoral fellowships from the Lavoisier programme of the ‘Ministères des Affaires étrangères’ and from the Centre National d'Etudes Spatiales (France). Support for the project and paper was provided by the Cassini Project and by the INSU ‘Programme National de Planétologie’.

Author information

Authors and Affiliations

  1. Laboratoire de Planétologie et Géodynamique, UMR-CNRS 6112, Université de Nantes, 44322, Nantes, cedex 03, France

    Gabriel Tobie & Christophe Sotin

  2. Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, 85721, USA

    Gabriel Tobie & Jonathan I. Lunine

  3. Instituto di Fisica dello Spazio Interplanetario, INAF, Via del Fosso del Cavaliere 100, 00133, Roma, Italia

    Jonathan I. Lunine

Authors
  1. Gabriel Tobie
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Jonathan I. Lunine
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Christophe Sotin
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Gabriel Tobie.

Ethics declarations

Competing interests

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

Supplementary information

Supplementary Notes

This file is divided into two sections. Section 1 provides physical data on the density of different materials composing Titan’s interior and on the stability curves of methane clathrate in presence of ammonia. Section 2 provides a detailed description of our long-term evolution model, and it is subdivided in 4 subsections. This file also contains additional references. (DOC 898 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Tobie, G., Lunine, J. & Sotin, C. Episodic outgassing as the origin of atmospheric methane on Titan. Nature 440, 61–64 (2006). https://doi.org/10.1038/nature04497

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature04497

This article is cited by

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.

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing