Evidence for subduction in the ice shell of Europa

Abstract

Jupiter’s icy moon Europa has one of the youngest planetary surfaces in the Solar System, implying rapid recycling by some mechanism. Despite ubiquitous extension and creation of new surface area at dilational bands that resemble terrestrial mid-ocean spreading zones, there is little evidence of large-scale contraction to balance the observed extension or to recycle ageing terrains. We address this enigma by presenting several lines of evidence that subduction may be recycling surface material into the interior of Europa’s ice shell. Using Galileo spacecraft images, we produce a tectonic reconstruction of geologic features across a 134,000 km2 region of Europa and find, in addition to dilational band spreading, evidence for transform motions along prominent strike-slip faults, as well as the removal of approximately 20,000 km2 of the surface along a discrete tabular zone. We interpret this zone as a subduction-like convergent boundary that abruptly truncates older geological features and is flanked by potential cryolavas on the overriding ice. We propose that Europa’s ice shell has a brittle, mobile, plate-like system above convecting warmer ice. Hence, Europa may be the only Solar System body other than Earth to exhibit a system of plate tectonics.

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Figure 1: Study region.
Figure 2: Interpretation of prominent geologic units and tectonic reconstruction.
Figure 3: Plate boundary morphologies.
Figure 4: Conceptual model for subduction.

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Acknowledgements

Images used in this analysis are available through the NASA Planetary Data System (PDS) Imaging Node at http://pds-imaging.jpl.nasa.gov/holdings/. We thank C. Cooper for input on geodynamic considerations, H. Meyer for assistance with image mosaics in ArcGIS, and P. Figueredo for sharing original data on surface area calculations for dilational bands. Artwork for Fig. 4 was created by N. Kroese.

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S.A.K. was responsible for the tectonic reconstructions of the study area. L.M.P. was responsible for the morphological analyses of the boundaries. Both authors contributed to the interpretation and analysis and to the preparation and finalization of the manuscript.

Corresponding author

Correspondence to Simon A. Kattenhorn.

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The authors declare no competing financial interests.

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Kattenhorn, S., Prockter, L. Evidence for subduction in the ice shell of Europa. Nature Geosci 7, 762–767 (2014). https://doi.org/10.1038/ngeo2245

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