New research casts doubt on the prospects for a habitable, active environment beneath the frozen surface of Jupiter’s moon Europa.
Europa has long been considered the most promising hope for life among Jupiter’s 95 known moons, and even in the entire solar system. Yet a new study led by Professor Paul Byrne with Washington University in St. Louis suggests that Europa is likely much less habitable than once hoped for.
The findings were revealed in a recent paper published in Nature Communications.
Calculating Europa’s Habitable Traits
The new work is not based on direct observations, but on calculations from models focused on several aspects of Europa that include its size, rocky core, and the gravitational field of its host planet, Jupiter. In addition to drawing from what is known about Europa, the recent calculations were also based on comparisons with information from other bodies in the solar system, such as Earth and the Moon.
Byrne’s team’s results indicate that the necessary activity required to spark a habitable environment in the salty ocean beneath the moon’s icy surface, such as tectonic motion, warm hydrothermal vents, and underwater geologic activity, is likely absent on Europa.
“If we could explore that ocean with a remote-control submarine, we predict we wouldn’t see any new fractures, active volcanoes, or plumes of hot water on the seafloor,” Byrne said. “Geologically, there’s not a lot happening down there. Everything would be quiet.”
Such inactive seafloor geology makes Europa’s habitability highly unlikely, as it lacks the energy and dynamic processes required to sustain life at the base of the ecosystem.
“The energy just doesn’t seem to be there to support life, at least today,” Byrne explained.
Conditions on Europa
Astronomers believe Europa’s ice shell extends for between 15 and 25 kilometers below the surface. The amount of water held there is tremendous; despite the tiny moon being smaller than our own natural satellite, it is believed to contain a vast ocean beneath its icy shell—perhaps even more than our own planet.
Europa’s core is at once similar to and quite different from that of Earth: it has a similar rocky composition, yet its interior likely cooled billions of years ago, in contrast to Earth’s extreme core temperatures.
Byrne’s conclusion about an inactive Europa may seem counterintuitive, as Jupiter’s moon Io is the most volcanically active body in the solar system. Jupiter’s gravitational forces can be potent, roiling tides and heating subsurface rocks on Io. However, Io differs from Europa in one major way that accounts for these divergent conditions. Io has an erratic orbit that brings it quite close to Jupiter, under the strong influence of the planet’s gravity. In contrast, Europa’s steady orbit keeps the icy moon quite distant from its host planet.
“Europa likely has some tidal heating, which is why it’s not completely frozen,” Byrne said. “And it may have had a lot more heating in the distant past. But we don’t see any volcanoes shooting out of the ice today like we see on Io, and our calculations suggest that the tides aren’t strong enough to drive any sort of significant geologic activity at the seafloor.”
Ongoing Intrigue
Even if it possesses no life, Byrne still contends that Europa is a fascinating focus of ongoing scientific study for other reasons.
“I’m really interested to know what that seafloor looks like,” he said. “For all of the talk about the ocean itself, there has been little discussion about the seafloor.”
Exactly what is occurring on Europa will come into clearer focus in the coming years with new missions aimed at providing direct observations of the icy moon. Among the missions Byrne anticipates the most is the Europa Clipper’s scheduled 2031 flyby of the icy moon, during which the spacecraft will take close-up images and detailed measurements of the ocean and ice cap.
“Those measurements should answer a lot of questions and give us more certainty,” Byrne said.
“I’m not upset if we don’t find life on this particular moon,” he concluded. “I’m confident that there is life out there somewhere, even if it’s 100 light-years away. That’s why we explore—to see what’s out there.”
The paper, “Little to No Active Faulting Likely at Europa’s Seafloor Today,” appeared in Nature Communications on January 6, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.