Impact of melt accumulation on tidal heat production in Europa’s rocky mantle

Volcanic activity at Europa’s seafloor is a key question in assessing the habitability of its subsurface ocean. The conditions required for seafloor hydrothermalism are largely governed by the heat flux from the underlying silicate mantle, driven by both radiogenic and tidal heating. The orbital resonance between Io, Europa, and Ganymede maintains non-zero orbital eccentricities and forces periodic tidal deformation. On Io, this results in extreme tidal heating and intense volcanism. Although tidal heating in Europa’s mantle is expected to be weaker due to its greater distance from Jupiter, Běhounková et al. [1] showed that it could still sustain partial melting in the mantle over tens to hundreds of millions of years, particularly during phases of elevated eccentricity. Given the likely inefficiency of melt extraction through Europa’s thick lithosphere [2, 3], melt produced during these periods may accumulate at depth. Such accumulation modifies the mantle’s viscoelastic properties and can in turn enhance tidal dissipation, which could lead to a positive feedback loop similar to the processes inferred for Io [4].

In this context, our study evaluates how melt accumulation in Europa’s rocky mantle affects tidal heat production with depth, tidal heat flow pattern and phase lag. We build on an existing viscoelastic tidal model developed for Io’s partially molten interior [4], adapting it to Europa’s structure following the 3D predictions of Běhounková et al. [1]. We show that, whatever the partially molten layer thickness, melt accumulation increases tidal heat production and even exceed radiogenic heating for certain conditions. Additionally, melt accumulation significantly alters the spatial distribution of seafloor tidal heating. In particular, melt fractions exceeding 20% within a ∼100 km thick layer can lead to localized heat fluxes greater than 100 mW/m². Finally, according to our results, phase lag measurements with a precision of 0.1°–0.2°, which could not be achieved by Europa Clipper, would be necessary to provide critical insights into Europa’s mantle rheology. The potential presence of such melt accumulations may be, however, tested by future measurements by Europa Clipper and JUICE from the combined analysis of gravimetric, altimetric and magnetic data, which might reveal long-wavelength anomalies which could be confronted to our model predictions.

[1] Běhounková et al., GRL, 48(3), e2020GL090077 (2021),  [2] Bland and Elder, GRL, 49(5), e2021GL096939 (2022), [3] Green et al, Nature Astronomy (2025), [4] Kervazo et al., A&A, 650, A72 (2021).