Jupiter's moon, Europa, may have active volcanoes on its ocean floor

A new collaborative study between LPG, Charles University in Prague, and JPL-Caltech (Pasadena) shows that tidal heating would be able to maintain volcanic activity on the ocean floor of Jupiter's moon Europa.

Europa, one of Jupiter's four Galilean moons, is known to harbor a salty ocean beneath its icy crust, making it one of the most promising places to search for conditions favorable for the emergence of life outside of Earth. The habitability potential of this ocean is largely determined by the amount of energy that could be available on the ocean floor, which is not very constrained to date.

This new study, published recently in Geophysical Research Letters, shows how the moon could have enough internal heat to partially melt its rocky mantle, a process that could fuel volcanoes on the ocean floor. The 3D modeling implemented in this work provides for the first time detailed constraints on the effect of internal heating on the evolution of its rocky interior.

 

figure europe 2
On the left, Scientists’ findings suggest that the interior of Jupiter’s moon Europa may consist of an iron core, surrounded by a rocky mantle in direct contact with an ocean under the icy crust. New research models how internal heat may fuel volcanoes on the seafloor. Credits: NASA/JPL-Caltech/Michael Carroll ; on the right, distribution of volumes of molten rock produced in the European mantle predicted by the 3D model implemented by Behounkova et al. (2021)

 

The process behind this volcanic activity is related to the tidal forces generated by Jupiter on its moon.  As Europa orbits the gas giant, the interior of the icy moon periodically deforms. At each tidal cycle, a small part of the energy involved in these internal motions is converted into heat (for example, as a paper clip heats up when it is repeatedly bent). This phenomenon is called tidal heating. The more the mantle is deformed, the more heat is produced, which after a while leads to a fusion of the rocks.

A volcanic activity at the bottom of the European ocean is the subject of speculation for decades. By comparison, the moon Io of Jupiter is clearly volcanic. Hundreds of volcanoes there regularly erupt volcanically, releasing plumes of gas and dust, reaching altitudes of several hundred kilometers - an activity related to the same type of internal heating caused by tidal forces due to Jupiter. But, as Europa is farther from Jupiter than Io is, and is therefore
less distorted, a comparable activity under the icy surface
of Europa is still uncertain.

Simulations by Marie Behounkova and collaborators at the LPG show that volcanic activity may have occurred throughout Europa's history.  Although this activity is much weaker than on Io at present, it can be amplified during certain periods, in particular, when the orbit of Europa becomes more elliptical. Cyclic variations of Europa's orbit are expected due to gravitational interactions with the moons Io and Ganymede, via the so-called Laplace resonance. In addition, the authors show that the most recent volcanic activity is expected to be concentrated in the polar areas of Europa, where most of the tidal heat is generated. The volumes of lava produced in these active areas are comparable to the volumes emitted in the major volcanic provinces on Earth.

The existence of submarine volcanoes greatly enhances the exobiological potential of the Europa Ocean because they provide a local source of energy that can power hydrothermal systems, such as those that sustain life at the bottom of Earth's oceans. On Earth, when seawater comes into contact with hot magma, chemical energy is produced. It is the chemical energy of these hydrothermal systems, not sunlight, that helps sustain life deep in our oceans. Volcanic activity on the European seafloor would be one way to sustain a habitable environment.

These predictions can be tested when the NASA Europa Clipper and ESA JUICE missions, in which the LPG is involved, reach their targets early next decade. The Europa Clipper probe will make dozens of flights close to Europa, some below 25 km altitude.  This will be a unique opportunity to search for evidence of recent surface activity and to detect gases and minerals indicative of volcanic and hydrothermal activity. The high latitude flybys will allow to identify gravity and potentially magnetic anomalies confirming the concentration of volcanic activity at the poles. The complementarity between Europa Clipper and JUICE will allow us to reconstruct the recent history of the orbits of Europa, Io and Ganymede, and to evaluate the possibility that Europa has recently undergone a peak of volcanic activity.

 

Bibliographic reference
M. Běhounková, G. Tobie, G. Choblet, M. Kervazo, M. Melwani Daswani et C. Dumoulin et al. Tidally Induced Magmatic Pulses on the Oceanic Floor of Jupiter's Moon Europa, Geophysical Research Letters, Vol. 48, pp. e2020GL090077. 2021 - https://doi.org/10.1029/2020GL090077