Beneath the icy exterior of Jupiter's moon Europa lies one of the most promising places in the solar system to search for life. Later this year, NASA will launch a $5 billion mission called the Europa Clipper to study the ocean and potentially sample it.
Underneath the icy shell of Jupiter's moon Europa lies an ocean, but recent modeling studies presented by scientists at the 55th Lunar and Planetary Science Conference in Texas, USA, suggest that the rocky interior of Europa may be "geologically dead."
Magma might not be able to penetrate the seafloor to create hydrothermal vents, which are believed to be early havens for life on Earth, and Europa's rocky crust seems capable of resisting seismic ruptures, preventing the emergence of fresh rocks. Without the heat and fresh rocks driving geochemical reactions in the ocean, Europa is less likely to create conditions conducive to life.
Austin Green, a planetary scientist at NASA's Jet Propulsion Laboratory, called these findings a series of "disheartening conclusions." "If volcanic activity is a necessary condition for habitability, then Europa's ocean may not be suitable for life," he said.
These studies deal a blow to the habitability of Europa. Recent measurements taken by NASA's Juno spacecraft during a recent flyby of Europa, published in Nature Astronomy, show that radiation bombarding the icy shell would produce much less oxygen in the subsurface ocean than previously thought.
Additionally, efforts to find erupting plumes using NASA's James Webb Space Telescope have so far been unsuccessful, as reported in Science in 2023, casting doubt on the geysers discovered by the Hubble Space Telescope.
Paul Byrne, a planetary scientist at Washington University in St. Louis, reported at the conference that the focus of new research is on the deep rocks hidden beneath the ice layer and ocean of Europa, about 130 kilometers below the surface. "When we think of a cold world, we should also think of it as a rocky world. Because most of Europa's volume and mass is rock," Byrne said.
Byrne and his colleagues evaluated the strength of the lithosphere using two scenarios. The lithosphere is made up of rigid silicate rocks that make up the top layer of Europa's rocky interior. They then compared the calculated rock strength to the pressures they face, from Jupiter's gravity and the contraction as it cools over time. "I think nothing's happening on the seafloor," Byrne said.
Green and his colleagues took the opposite approach. They simulated molten rocks in Europa's mantle and observed how these magmas could rise within the lithosphere. The results not only struggled to produce melting but also reached only a few kilometers high, far below the seafloor. "They perform very poorly," Green said.
Byrne believes that Europa's past environment might have been more conducive to life. "Are conditions present at Europa's seafloor today that could sustain some form of biology?" he said. "Our results suggest that seems difficult. The scientific way to say it is 'maybe not.'"
