Amazing stuff!
"Habitability gets funky on worlds outside our own. While plants use sunlight for energy and animals, in turn, use plants, life in the subsurface oceans of icy moons has to find another way. New research suggests that primordial life could take advantage of radioactively decaying elements in rocks.
Typically, planetary scientists have thought that hydrothermal vents on Jupiter’s fourth-largest moon, Europa, spurred the rocky reactions needed to generate free energy for life in the form of movable electrons. ...
A team has theorized that trace radioactive elements in rocks, such as uranium-238 and phosphorus-40, might dissolve into the water over time, decaying and releasing heat. That heat could split apart water molecules, generating hydrogen and oxygen ions with available electrons—and thus energy for life. ..."
From the abstract:
"Europa and other icy ocean worlds have long been considered prime targets for astrobiology. Their potential for habitability has generally been thought to depend on chemical disequilibria produced by ongoing water-rock interaction. However, recent studies have raised questions about whether such interactions are currently active on Europa (Byrne et al. 2024, Austin et al. 2025). In addition to the ocean, the presence of liquid water bodies within the ice shell—so-called perched lakes--has been suggested (Schmidt et al. 2011). The latter represents another potential environment for future astrobiological exploration. Both of these environments where liquid water is present at Europa, but water-rock interaction may not currently be active, motivate consideration of alternative mechanisms for sustaining chemical energy sources.
We examine a novel mechanism in which the decay of radioactive isotopes (e.g., ⁴⁰K, 235U, ²³⁸U) drives liquid water radiolysis, generating local chemical disequilibria that could support microbial metabolism.
Our modeling shows that even low concentrations of these isotopes can produce both significant oxidants and reductants in aqueous environments without active water-rock interaction.
Depending on the salinity, these redox gradients could support approximately 1,000 microbial cells per liter under conditions similar to those inferred for Enceladus’s ocean, and up to 20,000 cells per liter at salinities comparable to terrestrial seawater. These values fall within the range of previous estimates for Europa’s ocean (~ 100-100,000 cells per liter, Hand+2017) and the equivalent biomass would be approximately 1023 - 1026 cells, comparable to the biomass of roughly 1,000-1,000,000 blue whales.
The decay of ⁴⁰K also leads to the production of ⁴⁰Ar, which could be detected by Europa Clipper’s MASPEX.
This mechanism offers a new perspective on the potential habitability of icy ocean worlds that may lack active water-rock interaction, i.e. Titan, Ganymede, and the Uranian moons."
Life in Europa’s ocean could feed on rocks’ radioactive decay "After series of bleak findings, theory sparks hope for alternative energy source within Jupiter’s intriguing moon"
Habitability Does Not Require Active Water-Rock Interaction: Radiogenic Salt-Driven Radiolysis as a Metabolic Energy Source on Europa (this appears to be a presentation)
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