Europa may lack active seafloor processes needed for sustained habitability.

A Nature Communications study models Europa’s rocky seafloor and finds it is likely too mechanically strong for widespread faulting, tectonics or hydrothermal activity that on Earth supports long-term rock–water chemical reactions; NASA’s Europa Clipper will make close flybys beginning in 2031 to assess the moon’s interior and any plume chemistry.

New research published in Nature Communications reassesses geological activity at the seafloor of Jupiter’s moon Europa and what that means for habitability. The authors combined rock-mechanics models with spacecraft-derived measurements to estimate the strength of Europa’s seafloor and the present-day stresses that could drive faulting or volcanism. Their conclusions indicate the modern seafloor is probably too strong for widespread tectonic deformation or the hydrothermal activity that on Earth sustains long-lived chemical energy sources for microbes. Europa still retains a very deep subsurface ocean and surface organics, and NASA’s Europa Clipper mission is scheduled to perform close flybys starting in 2031 to probe the moon’s interior and any plume material. What the study reports: - The modeled tidal stress at Europa’s seafloor is about 54 kPa, well below the MPa-scale stresses estimated as necessary to drive common faulting and seafloor failure. - The authors find that current tidal forcing, mantle convection, global contraction, and serpentinisation are all unlikely to generate frequent slip on pre-existing faults at the ocean floor. - Calculations place the brittle–plastic transition deep in the silicate interior (on the order of tens of kilometres) and estimate a thick, mechanically strong lithosphere. - Europa still meets some habitability criteria: a subsurface ocean estimated at roughly 40–100 miles deep beneath an ice shell about 10–15 miles thick, and organics detected on the surface. - The paper notes possible qualifiers: Europa could have been more geologically active in the past, and alternative processes such as radiolysis or limited microfracturing might provide some chemical energy even without widespread seafloor tectonics. Summary: If the seafloor is tectonically quiescent today, sustained rock–water reactions driven by faulting or hydrothermal venting would be limited, reducing a major long-term energy source for seafloor chemosynthetic ecosystems. The authors allow that past geological activity or other processes (for example, radiolysis) could have provided episodic or localized chemical energy. NASA’s Europa Clipper flybys, beginning in 2031, are expected to gather data that will help test whether water–rock interactions occur now or occurred in the past, and further constrain Europa’s internal structure and seafloor conditions.