A duo of geophysicists from Washington State University and Virginia Tech has uncovered a plausible pathway for nutrient transfer from the radiation-charged surface into the subsurface ocean of Jupiter’s icy moon Europa.
Artist’s concept of ocean on Jupiter’s moon Europa. Image credit: NASA / JPL-Caltech.
Europa contains more liquid water than all of Earth’s oceans combined, but its global ocean lies beneath a thick shell of ice that blocks sunlight.
The icy shell means that any life in Europa’s ocean has to find nutrient and energy sources other than the Sun, raising longstanding questions about how the ocean could be habitable.
Europa is also constantly bombarded by intense radiation from Jupiter.
The radiation interacts with salts and other materials on Europa’s surface to form useful nutrients for oceanic microbes.
Although there are several theories, planetary scientists are unsure of how that nutrient-rich surface ice can work through the icy shell layer to reach the ocean layer.
While Europa’s icy surface is highly geologically active due to Jupiter’s gravitational pull, the ice mostly shifts side to side rather than in the downward motion necessary for surface-ocean exchange.
Dr. Austin Green from Virginia Tech and Dr. Catherine Cooper from Washington State University decided to look to Earth for possible explanations and solutions to the surface recycling problem.
“This is a novel idea in planetary science, inspired by a well-understood idea in Earth science,” Dr. Green said.
“Most excitingly, this new idea addresses one of the longstanding habitability problems on Europa and is a good sign for the prospects of extraterrestrial life in its ocean.”
The authors zeroed in on the concept of crustal delamination, where a zone of crust is tectonically squeezed and chemically densified until it detaches and sinks into the mantle.
They thought this concept might apply to Europa, since various regions of the ice surface are enriched in densifying salts.
Other studies have shown that ice crystalline structure is weakened by included impurities and is less stable than pure ice.
However, to trigger delamination, the ice surface needs to be weakened in order to detach and sink within the icy shell interior.
The researchers proposed that the denser, saltier ice surrounded by pure ice would sink into the interior of the ice shell, providing a means of recycling Europa’s surface and feeding the ocean.
Using computer modeling, they determined that nutrient-rich surface ice can sink all the way to the base of the ice shell for almost any salt content, provided there is at least a little weakening in the surface ice.
The process is also relatively rapid and could be a consistent means of recycling ice and providing nutrients into Europa’s ocean.
The team’s paper was published in the Planetary Science Journal.
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A.P. Green & C.M. Cooper. 2026. Dripping to Destruction: Exploring Salt-driven Viscous Surface Convergence in Europa’s Icy Shell. Planet. Sci. J 7, 13; doi: 0.3847/PSJ/ae2b6f
