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Liquid water on Enceladus from observations of ammonia and 40Ar in the plume

A Corrigendum to this article was published on 27 August 2009

Abstract

Jets of water ice from surface fractures near the south pole1 of Saturn’s icy moon Enceladus produce a plume of gas and particles2,3,4,5. The source of the jets may be a liquid water region under the ice shell—as suggested most recently by the discovery of salts in E-ring particles derived from the plume6—or warm ice that is heated, causing dissociation of clathrate hydrates7. Here we report that ammonia is present in the plume, along with various organic compounds, deuterium and, very probably, 40Ar. The presence of ammonia provides strong evidence for the existence of at least some liquid water, given that temperatures in excess of 180 K have been measured near the fractures from which the jets emanate8. We conclude, from the overall composition of the material, that the plume derives from both a liquid reservoir (or from ice that in recent geological time has been in contact with such a reservoir) as well as from degassing, volatile-charged ice.

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Figure 1: Mass spectrum on 9 October 2008.
Figure 2: Histogram showing the INMS spectrum over the mass range 34–48 Da.
Figure 3: Comparison of volatile abundances observed in Enceladus’ plume with those seen in cometary comae.

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Acknowledgements

Support by the Cassini Project through a subcontract with Southwest Research Institute is acknowledged.

Author Contributions J.H.W. organized and coordinated the plume composition study. J.H.W., C.R.G., W.S.L., J.I.L., W.B.M., O.M., M.-J.N. and J.W. developed the concept of the Letter and the interpretation of the INMS data. W.S.L., J.I.L., W.B.M., C.R.G. and O.M. worked jointly to write the manuscript. B.A.M. analysed the data and prepared the spectra. D.T.Y., T.B. and B.D.T. analysed the physical and chemical interactions of the inflowing material with the INMS antechamber and, together with B.A.M. and C.R.G., prepared the Supplementary Information. H.B.N. provided calibration support and information about instrument performance. R.L.M., M.P. and W.-H.I. provided supporting analysis of the neutral and ion environment surrounding Enceladus.

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Correspondence to W. S. Lewis.

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This file contains Supplementary Methods and Data, Supplementary Figures S1-S4, Supplementary Tables S1-S7 and Supplementary References. (PDF 1491 kb)

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Waite Jr, J., Lewis, W., Magee, B. et al. Liquid water on Enceladus from observations of ammonia and 40Ar in the plume. Nature 460, 487–490 (2009). https://doi.org/10.1038/nature08153

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