Tectonic breathing of icy moon Europa: Could subduction- and rifting-like processes support habitability in the outer solar system?

The geologically young surface of Jupiter’s icy moon Europa shows multiple lines of evidence for both divergent and convergent tectonic activity: dilation bands, where fresh ice has been emplaced, and regions interpreted as “subduction” zones, where ice appears to have descended under the surface. These motions are likely driven by cyclic global expansion and contraction of the ice shell resulting from long-term variations of Europa’s orbital eccentricity. We show that resulting vertical transport of chemical compounds across the ice shell possibly allows for transient habitable conditions within the subsurface ocean. The efficiency of this exchange depends on the amplitude and frequency of eccentricity variations, and we demonstrate that the present-day area of Europa’s dilation bands can only be explained by multiple episodes of ice shell thinning and thickening during Europa's surface age. However, given that the age is only ?180 Myr, this interpretation is inconsistent with thermo-orbital models, which predict the eccentricity variations on time scales of hundreds of millions of years. We discuss several possible explanations to this paradox, yet each of them is in conflict with present-day knowledge of Europa's thermal and orbital evolution.

Speaker: Martin Kihoulou, UC Santa Cruz

Room 350/372

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