Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures

Abstract

The icy surface of Jupiter’s moon, Europa, is thought to lie on top of a global ocean1,2,3,4. Signatures in some Hubble Space Telescope images have been associated with putative water plumes rising above Europa’s surface5,6, providing support for the ocean theory. However, all telescopic detections reported were made at the limit of sensitivity of the data5,6,7, thereby calling for a search for plume signatures in in-situ measurements. Here, we report in-situ evidence of a plume on Europa from the magnetic field and plasma wave observations acquired on Galileo’s closest encounter with the moon. During this flyby, which dropped below 400 km altitude, the magnetometer8 recorded an approximately 1,000-kilometre-scale field rotation and a decrease of over 200 nT in field magnitude, and the Plasma Wave Spectrometer9 registered intense localized wave emissions indicative of a brief but substantial increase in plasma density. We show that the location, duration and variations of the magnetic field and plasma wave measurements are consistent with the interaction of Jupiter’s corotating plasma with Europa if a plume with characteristics inferred from Hubble images were erupting from the region of Europa’s thermal anomalies. These results provide strong independent evidence of the presence of plumes at Europa.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Galileo MAG data for the E12 flyby.
Fig. 2: Galileo plasma wave data and derived plasma density for the E12 flyby.
Fig. 3: Location of the modelled plume on Europa’s surface.

References

  1. 1.

    Khurana, K. K. et al. Induced magnetic fields as evidence for subsurface oceans in Europa and Callisto. Nature 395, 777–780 (1998).

    ADS  Article  Google Scholar 

  2. 2.

    Carr, M. H. et al. Evidence for a subsurface ocean on Europa. Nature 391, 363–365 (1998).

    ADS  Article  Google Scholar 

  3. 3.

    Pappalardo, R. T. et al. Does Europa have a subsurface ocean? Evaluation of the geological evidence. J. Geophys. Res. 104, 24105–24055 (1999).

    ADS  Article  Google Scholar 

  4. 4.

    Kivelson, M. G. et al. Galileo magnetometer measurements strengthen the case for a subsurface ocean at Europa. Science 289, 1340–1343 (2000).

    ADS  Article  Google Scholar 

  5. 5.

    Roth, L. et al. Transient water vapor at Europa’s south pole. Science 343, 171–174 (2014).

    ADS  Article  Google Scholar 

  6. 6.

    Sparks, W. B. et al. Probing for evidence of plumes on Europa with HST/STIS. Astrophys. J. 829, 121 (2016).

    ADS  Article  Google Scholar 

  7. 7.

    Sparks, W. B. et al. Active cryovolcanism on Europa? Astrophys. J. Lett. 839, L18 (2017).

    ADS  Article  Google Scholar 

  8. 8.

    Kivelson, M. G., Khurana, K. K., Means, J. D., Russell, C. T. & Snare, R. C. The Galileo magnetic field investigation. Space Sci. Rev. 60, 357–383 (1992).

    ADS  Article  Google Scholar 

  9. 9.

    Gurnett, D. A. et al. The Galileo plasma wave investigation. Space Sci. Rev. 60, 341–355 (1992).

    ADS  Article  Google Scholar 

  10. 10.

    Roth, L. et al. Orbital apocenter is not a sufficient condition for HST/STIS detection of Europa’s water vapor aurora. Proc. Natl Acad. Sci. USA 111, E5123–E5132 (2014).

    ADS  Article  Google Scholar 

  11. 11.

    Spencer, J. R., Tamppari, L. K., Martin, T. Z. & Travis, L. D. Temperatures on Europa from Galileo photopolarimeter-radiometer: nighttime thermal anomalies. Science 284, 1514–1516 (1999).

    ADS  Article  Google Scholar 

  12. 12.

    McGrath, M. & Sparks, W. B. Galileo ionosphere profile coincident with repeat plume detection location at Europa. Res. Notes AAS 1, 14 (2017).

    Article  Google Scholar 

  13. 13.

    Blöcker, A., Saur, J. & Roth, L. Europa’s plasma interaction with an inhomogeneous atmosphere: development of Alfvén winglets within the Alfvén wings. J. Geophys. Res. 121, 9794–9828 (2016).

    Article  Google Scholar 

  14. 14.

    Kurth, W. S. et al. The plasma wave environment of Europa. Planet. Space Sci. 49, 345–363 (2001).

    ADS  Article  Google Scholar 

  15. 15.

    Kivelson, M. G., Khurana, K. K. & Volwerk, M. in Europa (eds Pappalardo, R. T., McKinnon, W. B. & Khurana, K. K.) 545–570 (Univ. Arizona Press, Tucson, AZ, 2009).

  16. 16.

    Toth, G. et al. Adaptive numerical algorithms in space weather modeling. J. Comp. Phys. 231, 870–903 (2012).

    ADS  MathSciNet  Article  Google Scholar 

  17. 17.

    Rubin, M. et al. Self-consistent multi-fluid MHD simulations of Europa’s exospheric interaction with Jupiter’s magnetosphere. J. Geophys. Res. 120, 3503–3524 (2015).

    Article  Google Scholar 

  18. 18.

    Hall, D. T., Strobel, D. F. & Feldman, P. D., McGrath, M. A. & Weaver, H. A. Detection of an oxygen atmosphere on Jupiter’s moon Europa. Nature 373, 677–679 (1995).

    ADS  Article  Google Scholar 

  19. 19.

    Bagenal, F., Dougherty, L. P., Bodish, K. M., Richardson, J. D. & Belcher, J. M. Survey of Voyager plasma science ions at Jupiter: 1. Analysis method. J. Geophys. Res. 122, 8241–8256 (2017).

    Article  Google Scholar 

  20. 20.

    Porco, C. C. et al. Cassini observes the active south pole of Enceladus. Science 311, 1393–1401 (2006).

    ADS  Article  Google Scholar 

  21. 21.

    Neubauer, F. M. The sub-Alfvénic interaction of the Galilean satellites with the Jovian magnetosphere. J. Geophys. Res. 103, 19843–19866 (1998).

    ADS  Article  Google Scholar 

  22. 22.

    Grasset, O. et al. JUpiter ICy moons Explorer (JUICE): an ESA mission to orbit Ganymede and to characterise the Jupiter system. Planet. Space Sci. 78, 1–21 (2013).

    ADS  Article  Google Scholar 

  23. 23.

    Pappalardo, R. et al. Science objectives and capabilities of the NASA Europa mission. In Proc. 47th Lunar and Planetary Science Conf. 3058 (Lunar and Planetary Institute, 2016).

  24. 24.

    Powell, K. G., Roe, P. L., Linde, T. J., Gombosi, T. I. & De Zeeuw, D. L. A solution-adaptive upwind scheme for ideal magnetohydrodynamics. J. Comp. Phys. 154, 284–309 (1999).

    ADS  MathSciNet  Article  MATH  Google Scholar 

  25. 25.

    Gombosi, T. I. et al. Semirelativistic magnetohydrodynamics and physics-based convergence acceleration. J. Comput. Phys. 177, 176–205 (2002).

    ADS  MathSciNet  Article  MATH  Google Scholar 

  26. 26.

    Kabin, K. et al. On Europa’s magnetospheric interaction: a MHD simulation of the E4 flyby. J. Geophys. Res. 104, 19983–19992 (1999).

    ADS  Article  Google Scholar 

  27. 27.

    Liu, Y. et al. Two-species, 3D MHD simulation of Europa’s interaction with Jupiter’s magnetosphere. Geophys. Res. Lett. 27, 1791–1794 (2000).

    ADS  Article  Google Scholar 

  28. 28.

    Hall, D. T., Feldman, P. D., McGrath, M. A. & Strobel, D. F. The far-ultraviolet oxygen airglow of Europa and Ganymede. Astrophys. J. 499, 475–481 (1998).

    ADS  Article  Google Scholar 

  29. 29.

    McGrath, M. A., Hansen, C. J. & Hendrix, A. R. in Europa (eds Pappalardo, R. T., McKinnon, W. B. & Khurana, K. K.) 485–505 (Univ. Arizona Press, Tucson, AZ, 2009).

  30. 30.

    Shematovich, V. I., Johnson, R. E., Cooper, J. F. & Wong, M. C. Surface-bounded atmosphere of Europa. Icarus 173, 480–498 (2005).

    ADS  Article  Google Scholar 

  31. 31.

    Smyth, W. H. & Marconi, M. L. Europa’s atmosphere, gas tori, and magnetospheric implications. Icarus 181, 510–526 (2006).

    ADS  Article  Google Scholar 

  32. 32.

    Cassidy, T. A., Johnson, R. E., McGrath, M. A., Wong, M. C. & Cooper, J. F. The spatial morphology of Europa’s near-surface O2 atmosphere. Icarus 191, 755–764 (2007).

    ADS  Article  Google Scholar 

  33. 33.

    Plainaki, C. et al. The role of sputtering and radiolysis in the generation of Europa exosphere. Icarus 218, 956–966 (2012).

    ADS  Article  Google Scholar 

  34. 34.

    Saur, J., Strobel, D. F. & Neubauer, F. M. Interaction of the Jovian magnetosphere with Europa: constraints on the neutral atmosphere. J. Geophys. Res. 103, 19947–19962 (1998).

    ADS  Article  Google Scholar 

  35. 35.

    Johnson, R. E. et al. in Europa (eds Pappalardo, R. T., McKinnon, W. B. & Khurana, K. K.) 507–528 (Univ. Arizona Press, Tucson, AZ, 2009).

  36. 36.

    Schilling, N., Neubauer, F. M. & Saur, J. Influence of the internally induced magnetic field on the plasma interaction of Europa. J. Geophys. Res. 113, A03203 (2008).

    ADS  Article  Google Scholar 

  37. 37.

    Dols, V., Bagenal, F., Cassidy, T., Crary, F. J. & Delamere, P. A. Europa’s atmospheric neutral escape: importance of symmetrical O2 charge exchange. Icarus 264, 387–397 (2016).

    ADS  Article  Google Scholar 

  38. 38.

    Schunk, R. & Nagy, A. Ionospheres: Physics, Plasma Physics, and Chemistry (Cambridge Univ. Press, Cambridge, UK, 2009).

    Google Scholar 

  39. 39.

    Bagenal, F. et al. Plasma conditions at Europa’s orbit. Icarus 261, 1–13 (2015).

    ADS  Article  Google Scholar 

  40. 40.

    Zimmer, C., Khurana, K. K. & Kivelson, M. G. Subsurface oceans on Europa and Callisto: constraints from Galileo magnetometer observations. Icarus 147, 329–347 (2000).

    ADS  Article  Google Scholar 

Download references

Acknowledgements

We thank M. McGrath for an illuminating presentation at a Europa Clipper Project Science Group meeting on observations of Europa’s plumes, which led us to re-examine the Galileo MAG data on which this paper is largely based. The work at the University of Michigan was supported by NASA through grants #NNX12AM74G and #NNX15AH28G, contract #1532308 through the Jet Propulsion Laboratory and contract #143448 through the Applied Physics Laboratory at Johns Hopkins University. The research at the University of Iowa is supported by NASA through contract UTA16-001080 through the University of Texas at Austin. Additional funding for work at UCLA was provided by NASA grants #NNX13AL05G:000002 and #NNX14AO24G.

Author information

Affiliations

Authors

Contributions

X.J., M.G.K. and K.K.K. contributed to the analysis of the Galileo magnetic field data. W.S.K. analysed the Galileo plasma wave data. X.J. performed the simulations and led the interpretation of the model results. All authors discussed the results and contributed to writing the manuscript.

Corresponding author

Correspondence to Xianzhe Jia.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figures 1–5.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Jia, X., Kivelson, M.G., Khurana, K.K. et al. Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures. Nat Astron 2, 459–464 (2018). https://doi.org/10.1038/s41550-018-0450-z

Download citation

Further reading

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