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# The water abundance in Jupiter’s equatorial zone

## Abstract

Oxygen is the most common element after hydrogen and helium in Jupiter’s atmosphere, and may have been the primary condensable (as water ice) in the protoplanetary disk. Prior to the Juno mission, in situ measurements of Jupiter’s water abundance were obtained from the Galileo probe, which dropped into a meteorologically anomalous site. The findings of the Galileo probe were inconclusive because the concentration of water was still increasing when the probe ceased sending data. Here we report on the water abundance in the equatorial region (0 to 4 degrees north latitude), based on data taken at 1.25 to 22 GHz from the Juno microwave radiometer, probing pressures of approximately 0.7 to 30 bar. Because Juno discovered the deep atmosphere to be surprisingly variable as a function of latitude, it remains to confirm whether the equatorial abundance represents Jupiter’s global water abundance. The water abundance at the equatorial region is inferred to be $$2.5_{ - 1.6}^{ + 2.2} \times 10^3$$ ppm, or $$2.7_{ - 1.7}^{ + 2.4}$$ times the elemental ratio of protosolar oxygen to hydrogen (1σ uncertainties). If this reflects the global water abundance, the result suggests that the planetesimals that formed Jupiter were unlikely to have been water-rich clathrate hydrates.

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## Data availability

Juno MWR data can be accessed on the Planetary Data System (PDS) https://pds.nasa.gov/. Requests for all other data or materials that are presented in the paper but not archived in the PDS should be addressed to C.L.

## References

1. Weidenschilling, S. & Lewis, J. Atmospheric and cloud structures of the Jovian planets. Icarus 20, 465–476 (1973).

2. Atreya, S. K. & Wong, A.-S. Coupled clouds and chemistry of the giant planets—a case for multiprobes. Space Sci. Rev. 116, 121–136 (2005).

3. Lewis, J. S. & Prinn, R. G. Jupiter’s clouds: structure and composition. Science 169, 472–473 (1970).

4. Gierasch, P. J. Jovian meteorology: large-scale moist convection. Icarus 29, 445–454 (1976).

5. Gierasch, P. J. et al. Observation of moist convection in Jupiter’s atmosphere. Nature 403, 628 (2000).

6. Wong, M. H. et al. Oxygen and other volatiles in the giant planets and their satellites. Rev. Mineral. Geochem. 68, 219–246 (2008).

7. Young, R. E., Smith, M. A. & Sobeck, C. K. Galileo probe: in situ observations of Jupiter’s atmosphere. Science 272, 837–838 (1996).

8. Orton, G. S. et al. Characteristics of the Galileo probe entry site from Earth-based remote sensing observations. J. Geophys. Res. Planets 103, 22791–22814 (1998).

9. Niemann, H. et al. The composition of the Jovian atmosphere as determined by the Galileo probe mass spectrometer. J. Geophys. Res. Planets 103, 22831–22845 (1998).

10. Wong, M. H., Mahaffy, P. R., Atreya, S. K., Niemann, H. B. & Owen, T. C. Updated Galileo probe mass spectrometer measurements of carbon, oxygen, nitrogen, and sulfur on Jupiter. Icarus 171, 153–170 (2004).

11. Showman, A. P. & Ingersoll, A. P. Interpretation of Galileo probe data and implications for Jupiter’s dry downdrafts. Icarus 132, 205–220 (1998).

12. Owen, T. et al. A low-temperature origin for the planetesimals that formed Jupiter. Nature 402, 269 (1999).

13. Mousis, O., Lunine, J. I., Madhusudhan, N. & Johnson, T. V. Nebular water depletion as the cause of Jupiter’s low oxygen abundance. Astrophys. J. Lett. 751, L7 (2012).

14. Gautier, D., Hersant, F., Mousis, O. & Lunine, J. I. Enrichments in volatiles in Jupiter: a new interpretation of the Galileo measurements. Astrophys. J. 550, L227–L230 (2001).

15. Owen, T. & Encrenaz, T. Element abundances and isotope ratios in the giant planets and Titan. Space Sci. Rev. 106, 121–138 (2003).

16. Helled, R. & Lunine, J. Measuring Jupiter’s water abundance by Juno: the link between interior and formation models. Mon. Not. R. Astron. Soc. 441, 2273–2279 (2014).

17. Lunine, J. I. & Hunten, D. M. Moist convection and the abundance of water in the troposphere of Jupiter. Icarus 69, 566–570 (1987).

18. Li, C. & Ingersoll, A. P. Moist convection in hydrogen atmospheres and the frequency of Saturn’s giant storms. Nat. Geosci. 8, 398–403 (2015).

19. Janssen, M. A. et al. MWR: microwave radiometer for the Juno mission to Jupiter. Space Sci. Rev. 213, 139–185 (2017).

20. Li, C. et al. The distribution of ammonia on Jupiter from a preliminary inversion of Juno microwave radiometer data. Geophys. Res. Lett. 44, 5317–5325 (2017).

21. Brown, S. et al. Prevalent lightning sferics at 600 megahertz near Jupiter’s poles. Nature 558, 87 (2018).

22. Bolton, S. J. et al. Jupiter’s interior and deep atmosphere: the initial pole-to-pole passes with the Juno spacecraft. Science 356, 821–825 (2017).

23. Achterberg, R. K., Conrath, B. J. & Gierasch, P. J. Cassini CIRS retrievals of ammonia in Jupiter’s upper troposphere. Icarus 182, 169–180 (2006).

24. de Pater, I., Sault, R., Butler, B., DeBoer, D. & Wong, M. H. Peering through Jupiter’s clouds with radio spectral imaging. Science 352, 1198–1201 (2016).

25. Li, C. & Chen, X. Simulating Nonhydrostatic Atmospheres on Planets (SNAP): formulation, validation, and application to the Jovian atmosphere. Astrophys. J. Suppl. Ser. 240, 37 (2019).

26. Lindal, G. F. et al. The atmosphere of Jupiter: an analysis of the Voyager radio occultation measurements. J. Geophys. Res. Space Phys. 86, 8721–8727 (1981).

27. Bellotti, A., Steffes, P. G. & Chinsomboon, G. Corrigendum to “Laboratory measurements of the 5-20 cm wavelength opacity of ammonia, water vapor, and methane under simulated conditions for the deep jovian atmosphere” [Icarus 280 (2016) 255–267]. Icarus 284, 491–492 (2017).

28. Asplund, M., Grevesse, N., Sauval, A. J. & Scott, P. The chemical composition of the Sun. Ann. Rev. Astron. Astrophys. 47, 481–522 (2009).

29. Atreya, S. K. et al. in Saturn in the 21st Century Vol. 20, 5–43 (eds Baines, K. H. et al.) (Cambridge Univ. Press, 2019).

30. Folkner, W. M., Woo, R. & Nandi, S. Ammonia abundance in Jupiter’s atmosphere derived from the attenuation of the Galileo probe’s radio signal. J. Geophys. Res. Planets 103, 22847–22855 (1998).

31. de Pater, I. et al. Jupiter’s ammonia distribution derived from VLA maps at 3–37 GHz. Icarus 322, 168–191 (2019).

32. Bjoraker, G. L. et al. The gas composition and deep cloud structure of Jupiter’s Great Red Spot. Astron. J. 156, 101 (2018).

33. Leconte, J., Selsis, F., Hersant, F. & Guillot, T. Condensation-inhibited convection in hydrogen-rich atmospheres—stability against double-diffusive processes and thermal profiles for Jupiter, Saturn, Uranus, and Neptune. Astron. Astrophys. 598, A98 (2017).

34. Friedson, A. J. & Gonzales, E. J. Inhibition of ordinary and diffusive convection in the water condensation zone of the ice giants and implications for their thermal evolution. Icarus 297, 160–178 (2017).

35. Lodders, K. Jupiter formed with more tar than ice. Astrophys. J. 611, 587–597 (2004).

36. Ingersoll, A. P., Kanamori, H. & Dowling, T. E. Atmospheric gravity waves from the impact of comet Shoemaker-Levy 9 with Jupiter. Geophys. Res. Lett. 21, 1083–1086 (1994).

37. Allison, M. Planetary waves in Jupiter’s equatorial atmosphere. Icarus 83, 282–307 (1990).

38. Fletcher, L. N. et al. Retrievals of atmospheric variables on the gas giants from ground-based mid-infrared imaging. Icarus 200, 154–175 (2009).

39. Goodman, J. & Weare, J. Ensemble samplers with affine invariance. Commun. Appl. Math. Comput. Sci. 5, 65–80 (2010).

40. Li, C., Ingersoll, A. P. & Oyafuso, F. Moist adiabats with multiple condensing species: a new theory with application to giant-planet atmospheres. J. Atmos. Sci. 75, 1063–1072 (2018).

## Acknowledgements

The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The Juno mission and the team members at the Jet Propulsion Laboratory were supported by NASA grant NNN12AA01C. T.G. acknowledges support from CNRS. We thank all Juno team members for the collaborative efforts.

## Author information

Authors

### Contributions

C.L. developed the inversion software and performed the data analysis. All authors discussed the results and commented on the manuscript.

### Corresponding author

Correspondence to Cheng Li.

## 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.

## Extended data

### Extended Data Fig. 1 Limb-darkening error of the fitting using a three-parameter formula.

Histogram of the difference between the limb-darkening at 45° calculated using equation (4)—R(fit)—and using a radiative transfer model— R(model)—for a wide range of model atmospheres.

### Extended Data Fig. 2 Brightness temperature error of the fitting using a three-parameter formula.

Histogram of the percentage difference between the brightness temperature calculated using equation (4)—$$T_{\mathrm{B}}^{\left( {{\mathrm{fit}}} \right)}$$—and using a radiative transfer model—$$T_{\mathrm{B}}^{\left( {{\mathrm{model}}} \right)}$$—over a wide range of model atmospheres.

### Extended Data Fig. 3 Spacity pattern of the error covariance matrix.

Sparsity pattern of the covariance matrix of X* in equation (6) (10 GHz). The coefficients are aligned sequentially from a(ϕ) to b(ϕ) to c(ϕ). The dark region indicates that the covariance is large.

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Li, C., Ingersoll, A., Bolton, S. et al. The water abundance in Jupiter’s equatorial zone. Nat Astron 4, 609–616 (2020). https://doi.org/10.1038/s41550-020-1009-3

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• DOI: https://doi.org/10.1038/s41550-020-1009-3

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