Curtain eruptions from Enceladus’ south-polar terrain

Abstract

Observations of the south pole of the Saturnian moon Enceladus revealed large rifts in the south-polar terrain, informally called ‘tiger stripes’, named Alexandria, Baghdad, Cairo and Damascus Sulci. These fractures have been shown to be the sources of the observed jets of water vapour and icy particles1,2,3,4 and to exhibit higher temperatures than the surrounding terrain5,6. Subsequent observations have focused on obtaining close-up imaging of this region to better characterize these emissions. Recent work7 examined those newer data sets and used triangulation of discrete jets3 to produce maps of jetting activity at various times. Here we show that much of the eruptive activity can be explained by broad, curtain-like eruptions. Optical illusions in the curtain eruptions resulting from a combination of viewing direction and local fracture geometry produce image features that were probably misinterpreted previously as discrete jets. We present maps of the total emission along the fractures, rather than just the jet-like component, for five times during an approximately one-year period in 2009 and 2010. An accurate picture of the style, timing and spatial distribution of the south-polar eruptions is crucial to evaluating theories for the mechanism controlling the eruptions.

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Figure 1: Curtain simulations illustrating the phantom jet phenomenon.
Figure 2: Schematic illustrating the dependence of phantom jet locations on viewing angle.
Figure 3: Shadow anomalies and spreading curtains.
Figure 4: Stereographic projections of the south-polar terrain showing activity at five different times, and the average.

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Acknowledgements

This work was funded by grant number NNX13AG45G of the Cassini Data Analysis and Participating Scientists Program. We thank M. Hedman, P. Thomas and C. Howett for conversations on this topic.

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Contributions

J.N.S. devised the approach and wrote the majority of the text. T.A.H. and A.R.R. contributed substantially to the interpretation and to the text. E.E.B. and S.S.P. digitized many of the fractures and contributed to early efforts that led to the current approach.

Corresponding author

Correspondence to Joseph N. Spitale.

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The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Portion of image N1602274088 showing source locations inferred from anomalous emission near Damascus Sulcus.

Diamonds are sample points inferred from the observed curtains; uncertainties are shown as circles about each displayed sample point. The inferred source locations correspond well with features that are not apparent in the base map.

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Spitale, J., Hurford, T., Rhoden, A. et al. Curtain eruptions from Enceladus’ south-polar terrain. Nature 521, 57–60 (2015). https://doi.org/10.1038/nature14368

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