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.

Discovery of a proton aurora at Mars

Abstract

Proton aurorae are a distinct class of auroral phenomena caused by energetic protons precipitating into a planetary atmosphere. The defining observational signature is atomic hydrogen emissions from the precipitating particles after they obtain an electron from the neutral atmospheric gas, a process known as charge exchange. Until now, proton aurorae have been observed at Earth only. Here, we present evidence of auroral activity driven by precipitating protons at Mars, using observations by the MAVEN spacecraft. We observed transient brightening of upper atmospheric hydrogen Lyman-α emission across the Martian dayside correlated with solar wind activity. The driving mechanism is one not found at Earth and originates from energetic neutral atom production by solar wind protons directly interacting with the extended hydrogen corona surrounding Mars. We characterize this new type of Martian aurora and compare the observed emissions with preliminary modelling guided by simultaneous in situ particle measurements. These observations provide insights into how the solar wind can directly deposit energy into the Martian atmosphere as well as all other planetary objects that are surrounded by a substantial neutral corona exposed to the solar wind.

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

Access options

\$32.00

All prices are NET prices.

References

1. Vegard, L. Hydrogen showers in the auroral region. Nature 144, 1089–1090 (1939).

2. Eather, R. H. Auroral proton precipitation and hydrogen emissions. Rev. Geophys. 5, 207–285 (1967).

3. Gérard, J.-C., Hubert, B., Bisikalo, D. V. & Shematovich, V. I. A model of the Lyman line profile in the proton aurora. J. Geophys. Res. 105, 15795–15806 (2000).

4. Hardy, D. A., Gussenhoven, M. S. & Brautigam, D. A statistical model of auroral ion precipitation. J. Geophys. Res. 94, 370–392 (1989).

5. Kallio, E. & Barabash, S. Atmospheric effects of precipitating energetic hydrogen atoms on the Martian atmosphere. J. Geophys. Res. 106, 165–177 (2001).

6. Frey, H. U. et al. Proton aurora in the cusp. J. Geophys. Res. 107, 1091 (2002).

7. Stephan, A. W., Chakrabarti, S. & Cotton, D. M. Evidence of ENA precipitation in the EUV dayglow. Geophys. Res. Lett. 27, 2865–2868 (2000).

8. Jakosky, B. M. et al. The Mars Atmosphere and Volatile Evolution (MAVEN) mission. Space Sci. Rev. 195, 3–48 (2015).

9. McClintock, W. E. et al. The Imaging Ultraviolet Spectrograph (IUVS) for the MAVEN mission. Space Sci. Rev. 195, 75–124 (2015).

10. Anderson, D. E.Jr & Hord, C. W. Mariner 6 and 7 ultraviolet spectrometer experiment: analysis of hydrogen Lyman-alpha data. J. Geophys. Res. 76, 6666–6673 (1971).

11. Chaufray, J. Y., Bertaux, J. L., Leblanc, F. & Quémerais, E. Observation of the hydrogen corona with SPICAM on Mars Express. Icarus 195, 598–613 (2008).

12. Chaffin, M. S. et al. Three-dimensional structure in the Mars H corona revealed by IUVS on MAVEN. Geophys. Res. Lett. 42, 9001–9008 (2015).

13. Halekas, J. S. et al. The Solar Wind Ion Analyzer for MAVEN. Space Sci. Rev. 195, 125–151 (2015).

14. Halekas, J. S. et al. MAVEN observations of solar wind hydrogen deposition in the atmosphere of Mars. Geophys. Res. Lett. 42, 8901–8909 (2015).

15. Halekas, J. S. Seasonal variability of the hydrogen exosphere of Mars. J. Geophys. Res. 122, 901–911 (2017).

16. Barth, C. A. et al. Mariner 6 and 7 ultraviolet spectrometer experiment: upper atmosphere data. J. Geophys. Res. 76, 2213–2227 (1971).

17. Leblanc, F., Chaufray, J. Y., Lilensten, J., Witasse, O. & Bertaux, J.-L. Martian dayglow as seen by the SPICAM UV spectrograph on Mars Express. J. Geophys. Res. 111, E09S11 (2006).

18. Jain, S. K. et al. The structure and variability of Mars upper atmosphere as seen in MAVEN/IUVS dayglow observations. Geophys. Res. Lett. 42, 9023–9030 (2015).

19. Fang, X., Liemohn, M. W., Kozyra, J. U. & Solomon, S. C. Quantification of the spreading effect of auroral proton precipitation. J. Geophys. Res. 109, A04309 (2004).

20. Fang, X., Lummerzheim, D. & Jackman, C. H. Proton impact ionization and a fast calculation method. J. Geophys. Res. 118, 5369–5378 (2013).

21. Basu, B., Jasperse, J. R., Robinson, R. M., Vondrak, R. R. & Evans, D. S. Linear transport theory of auroral proton precipitation—a comparison with observations. J. Geophys. Res. 92, 5920–5932 (1987).

22. Evans, J. S. et al. Retrieval of CO2 and N2 in the Martian thermosphere using dayglow observations by IUVS on MAVEN. Geophys. Res. Lett. 42, 9040–9049 (2015).

23. Bertaux, J.-L. et al. Discovery of an aurora on Mars. Nature 435, 790–794 (2005).

24. Schneider, N. M. et al. Discovery of diffuse aurora on Mars. Science 350, aad0313 (2015).

25. Kallio, E. S., Luhmann, J. G. & Barabash, S. Charge exchange near Mars: the solar wind absorption and energetic neutral atom production. J. Geophys. Res. 102, 22183–22197 (1997).

26. Diéval, C., Kallio, E., Stenberg, G., Barabash, S. & Jarvinen, R. Hybrid simulations of proton precipitation patterns onto the upper atmosphere of Mars. Earth Planets Space 64, 121–134 (2012).

27. Gunell, H. et al. First ENA observations at Mars: charge exchange ENAs produced in the magnetosheath. Icarus 182, 431–438 (2006).

28. Gombosi, T. I., Cravens, T. E., Nagy, A. F., Elphic, R. C. & Russell, C. T. Solar wind absorption by Venus. J. Geophys. Res. 85, 7747–7753 (1980).

29. Simon Wedlund, C. et al. The atmosphere of comet 67P/Churyumov-Gerasimenko diagnosed by charge-exchanged solar wind alpha particles. Astron. Astrophys. 587, A154 (2016).

30. Bertucci, C. et al. Titan’s interaction with the supersonic solar wind. Geophys. Res. Lett. 42, 193–200 (2015).

31. Vidal-Madjar, A. et al. An extended upper atmosphere around the extrasolar planet HD209458b. Nature 422, 143–146 (2003).

Acknowledgements

The MAVEN mission is supported by NASA through the Mars Exploration Program. J.-Y.C., F.M. and F.L. are funded by the programme ‘Systeme Solaire’ of Centre National d’Etudes Spatiales. A.S. is supported by the Belgian Fund for Scientific Research (FNRS).

Author information

Authors

Contributions

J.D., S.K.J. and M.S.C. performed the analysis. X.F. created and ran the precipitating particle transport model used here. J.S.H. provided SWIA measurements and guidance in using them. J.S.E. provided neutral atmosphere airglow retrievals. All authors contributed to the development of the instrument pipeline and/or data acquisition as well as interpretation and presentation of these results.

Corresponding author

Correspondence to J. Deighan.

Ethics declarations

Competing interests

The authors declare no competing interests.

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

Supplementary information

Supplementary Information

Supplementary Figures 1–4

Rights and permissions

Reprints and Permissions

Deighan, J., Jain, S.K., Chaffin, M.S. et al. Discovery of a proton aurora at Mars. Nat Astron 2, 802–807 (2018). https://doi.org/10.1038/s41550-018-0538-5

• Accepted:

• Published:

• Issue Date:

• DOI: https://doi.org/10.1038/s41550-018-0538-5

• Observations and Modeling of Martian Auroras

• S. A. Haider
• K. K. Mahajan
• J. C. Gérard

Space Science Reviews (2022)

• Mars’s glowing auroras snapped by Hope spacecraft

• Davide Castelvecchi

Nature (2021)