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Active formation of ‘chaos terrain’ over shallow subsurface water on Europa


Europa, the innermost icy satellite of Jupiter, has a tortured young surface1,2,3,4 and sustains a liquid water ocean1,2,3,4,5,6 below an ice shell of highly debated thickness1,2,3,4,5,7,8,9,10. Quasi-circular areas of ice disruption called chaos terrains are unique to Europa, and both their formation and the ice-shell thickness depend on Europa's thermal state1,2,3,4,5,7,8,9,10,11,12,13,14,15,16,17. No model so far has been able to explain why features such as Conamara Chaos stand above surrounding terrain and contain matrix domes10,18. Melt-through of a thin (few-kilometre) shell3,7,8 is thermodynamically improbable and cannot raise the ice10,18. The buoyancy of material rising as either plumes of warm, pure ice called diapirs1,9,10,11,12,13,14,15 or convective cells16,17 in a thick (>10 kilometres) shell is insufficient to produce the observed chaos heights, and no single plume can create matrix domes10,18. Here we report an analysis of archival data from Europa, guided by processes observed within Earth's subglacial volcanoes and ice shelves. The data suggest that chaos terrains form above liquid water lenses perched within the ice shell as shallow as 3 kilometres. Our results suggest that ice–water interactions and freeze-out give rise to the diverse morphologies and topography of chaos terrains. The sunken topography of Thera Macula indicates that Europa is actively resurfacing over a lens comparable in volume to the Great Lakes in North America.

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Figure 1: Conamara Chaos is dominated by long-wavelength topography.
Figure 2: Thera Macula is a region of likely active chaos production above a large liquid water lens.
Figure 3: A new hypothesis for chaos formation.


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We thank D. Young, K. Soderlund, A. Barr, J. Greenbaum, J. Leisner and D. MacAyeal for comments and discussions on the development of these concepts. B.E.S. was supported by a fellowship from the Vetlesen Foundation and the Institute for Geophysics of the Jackson School of Geosciences, University of Texas at Austin (UTIG). D.D.B. was supported by NASA, NSF and UTIG. NASA supported the work of G.W.P. and P.M.S.

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Authors and Affiliations



B.E.S. and D.D.B. conceived of and actively discussed this project. B.E.S. analysed Galileo imaging data, found and studied terrestrial analogue information, analysed results, formulated the model, calculated values, and wrote the paper. D.D.B. provided discussion and direction, and edited the paper. G.W.P. performed the FFT analysis of Conamara Chaos topography data. P.M.S. produced the original DEM of Conamara and the photoclinometry of Thera Macula.

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Correspondence to B. E. Schmidt.

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The authors declare no competing financial interests.

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Schmidt, B., Blankenship, D., Patterson, G. et al. Active formation of ‘chaos terrain’ over shallow subsurface water on Europa. Nature 479, 502–505 (2011).

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