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:

Saturn’s rotation period from its atmospheric planetary-wave configuration

Nature volume 460, pages 608–610 (2009)Cite this article

Abstract

The rotation period of a gas giant's magnetic field (called the System III reference frame) is commonly used to infer its bulk rotation1. Saturn's dipole magnetic field is not tilted relative to its rotation axis (unlike Jupiter, Uranus and Neptune), so the surrogate measure of its long-wavelength (kilometric) radiation is currently used to fix the System III rotation period2. The period as measured now by the Cassini spacecraft is up to ∼7 min longer3 than the value of 10 h 39 min 24 s measured 28 years ago by Voyager2. Here we report a determination of Saturn's rotation period based on an analysis of potential vorticity. The resulting reference frame (which we call System IIIw) rotates with a period of 10 h 34 min 13 ± 20 s. This shifted reference frame is consistent with a pattern of alternating jets on Saturn that is more symmetrical between eastward and westward flow. This suggests that Saturn's winds are much more like those of Jupiter than hitherto believed4.

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 1: Variation of limiting planetary wave angular velocity with latitude for Saturn and Jupiter.
Figure 2: Comparison of cloud-level zonal velocity profiles on Saturn and Jupiter as viewed in System IIIw and System III.

Similar content being viewed by others

References

  1. Seidelman, P. K. & Devine, N. Evaluation of Jupiter's longitudes in System III (1965). Geophys. Res. Lett. 4, 65–68 (1977)

    Article  ADS  Google Scholar 

  2. Desch, M. D. & Kaiser, M. L. Voyager measurement of the rotation period of Saturn’s magnetic field. Geophys. Res. Lett. 8, 253–256 (1981)

    Article  ADS  Google Scholar 

  3. Gurnett, D. A. et al. The variable rotation period of the inner region of Saturn's plasma disk. Science 316, 442–445 (2007)

    Article  CAS  ADS  Google Scholar 

  4. Aurnou, J. M. & Heimpel, M. H. Zonal jets in rotating convection with mixed mechanical boundary conditions. Icarus 169, 492–498 (2004)

    Article  ADS  Google Scholar 

  5. Giampieri, G., Dougherty, M. K., Smith, E. J. & Russell, C. T. A regular period for Saturn's magnetic field that may track its internal rotation. Nature 441, 62–64 (2006)

    Article  CAS  ADS  Google Scholar 

  6. Goldreich, P. & Farmer, A. J. Spontaneous axisymmetry breaking of the external magnetic field at Saturn. J. Geophys. Res. 112 A05225 10.1029/2006JA012163 (2007)

    Article  CAS  ADS  Google Scholar 

  7. Anderson, J. D. & Schubert, G. Saturn’s gravitational field, internal rotation, and interior structure. Science 317, 1384–1387 (2007)

    Article  CAS  ADS  Google Scholar 

  8. Dowling, T. E. A relationship between potential vorticity and zonal wind on Jupiter. J. Atmos. Sci. 50, 14–22 (1993)

    Article  ADS  Google Scholar 

  9. Dowling, T. E. Dynamics of Jovian atmospheres. Annu. Rev. Fluid Mech. 27, 293–334 (1995)

    Article  ADS  MathSciNet  Google Scholar 

  10. Dowling, T. E. Estimate of Jupiter’s deep zonal wind profile from Shoemaker-Levy 9 data and Arnol’d’s second stability criterion. Icarus 117, 439–442 (1995)

    Article  ADS  Google Scholar 

  11. Arnol’d, V. I. On an a priori estimate in the theory of hydrodynamical stability. [In Russian.] Izv. Vyssh. Ucheb. Zaved. Matematika 54, 3–5 (1966)

    Google Scholar 

  12. McIntyre, M. E. & Shepherd, T. G. An exact local conservation theorem for finite-amplitude disturbances to non-parallel shear flows with remarks on Hamiltonian structure and on Arnol’d stability theorems. J. Fluid Mech. 181, 527–565 (1987)

    Article  ADS  MathSciNet  Google Scholar 

  13. Charney, J. G. & Drazin, P. G. Propagation of planetary scale disturbances from the lower into the upper atmosphere. J. Geophys. Res. 66, 83–109 (1961)

    Article  ADS  Google Scholar 

  14. Lian, Y. & Showman, A. P. Deep jets on gas-giant planets. Icarus 194, 597–615 (2008)

    Article  ADS  Google Scholar 

  15. Ingersoll, A. P. & Pollard, D. Motion in the interiors and atmospheres of Jupiter and Saturn: scale analysis, anelastic equations, barotropic stability criterion. Icarus 52, 62–80 (1982)

    Article  ADS  Google Scholar 

  16. Read, P. L. et al. Mapping potential-vorticity dynamics on Jupiter. I: Zonal-mean circulation from Cassini and Voyager 1 data. Q. J. R. Meteorol. Soc. 132, 1577–1603 (2006)

    Article  ADS  Google Scholar 

  17. Read, P. L., Conrath, B. J., Fletcher, L. N., Gierasch, P. J. & Simon-Miller, A. A. Mapping potential vorticity dynamics on Saturn: zonal mean circulation from Cassini and Voyager data. Planet. Space. Sci. (in the press)

  18. Stone, P. H. Baroclinic adjustment. J. Atmos. Sci. 35, 561–571 (1978)

    Article  ADS  Google Scholar 

  19. Vasavada, A. R. & Showman, A. P. Jovian atmospheric dynamics: an update after Galileo and Cassini. Rev. Mod. Phys. 68, 1935–1996 (2005)

    MathSciNet  Google Scholar 

  20. Read, P. L. et al. Dynamics of convectively driven banded jets in the laboratory. J. Atmos. Sci. 64, 4031–4052 (2007)

    Article  ADS  Google Scholar 

  21. Stamp, A. P. & Dowling, T. E. Jupiter’s winds and Arnol’d’s second stability theorem: slowly moving waves and neutral stability. J. Geophys. Res. 98, 18847–18855 (1993)

    Article  ADS  Google Scholar 

  22. Helled, R., Schubert, G. & Anderson, J. D. Empirical models of pressure and density in Saturn's interior: implications for the helium concentration, its depth dependence, and Saturn's precession rate. Icarus 199, 368–377 (2009)

    Article  ADS  Google Scholar 

  23. Porco, C. C. et al. Cassini imaging of Jupiter’s atmosphere, satellites, and rings. Science 299, 1541–1547 (2003)

    Article  CAS  ADS  Google Scholar 

Download references

Acknowledgements

We are grateful to F. M. Flasar and the Cassini CIRS team for access to the data from which the potential vorticity profiles discussed here were computed. P.L.R. acknowledges support from the UK Science and Technology Facilities Council, T.E.D. acknowledges support from NASA's Planetary Atmospheres and Outer Planet Research Programs, and G.S. acknowledges support from NASA’s Planetary Atmospheres and Planetary Geology and Geophysics programs. We are grateful also to R. Helled for computing values of ρ0 and J2 for Saturn based on System IIIw.

Author Contributions P.L.R. obtained and processed the Cassini data, deriving potential vorticity and ω(α) profiles, and conducted the statistical analysis. T.E.D. made the original suggestion to investigate α(φ) and contributed to the interpretation of the results. G.S. provided additional insights into Saturn’s rotation, and all authors contributed to the text and discussion of results.

Author information

Authors and Affiliations

  1. Department of Physics, University of Oxford, Oxford OX1 3PU, UK

    P. L. Read

  2. Department of Physics & Astronomy, University of Louisville, Louisville, Kentucky 40292, USA,

    T. E. Dowling

  3. Department of Earth & Space Sciences, University of California, Los Angeles, California 90095-1567, USA,

    G. Schubert

Authors
  1. P. L. Read
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. T. E. Dowling
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. G. Schubert
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to P. L. Read.

PowerPoint slides

Rights and permissions

Reprints and permissions

About this article

Cite this article

Read, P., Dowling, T. & Schubert, G. Saturn’s rotation period from its atmospheric planetary-wave configuration. Nature 460, 608–610 (2009). https://doi.org/10.1038/nature08194

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature08194

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