Jupiter's core does not have a sharp boundary but gradually merges into its hydrogen-rich layers. This dilute core was first revealed by NASA's Juno spacecraft, sparking debate about how it formed. Earlier research proposed that an ancient impact with another large planetary body could have mixed Jupiter's center enough to produce this structure.
Researchers from Durham University, working with colleagues at NASA, SETI, CENSSS, and the University of Oslo, tested the hypothesis using high-resolution planetary impact simulations on the DiRAC COSMA supercomputer with the SWIFT open-source code. The models included improved methods for tracking how rock, ice, hydrogen, and helium mix during extreme impacts.
The results showed that even under extreme conditions, giant impacts did not yield a stable dilute core. Instead, displaced core materials re-settled quickly, maintaining a distinct separation from the outer hydrogen and helium layers.
The findings suggest that Jupiter's dilute core arose not from a dramatic collision but from the way the planet accumulated heavy and light elements during its growth and evolution. Saturn has also been found to have a dilute core, reinforcing the idea that such structures form gradually rather than through rare, catastrophic impacts.
Lead author Dr Thomas Sandnes of Durham University said, "It's fascinating to explore how a giant planet like Jupiter would respond to one of the most violent events a growing planet can experience. We see in our simulations that this kind of impact literally shakes the planet to its core - just not in the right way to explain the interior of Jupiter that we see today."
Dr Luis Teodoro of the University of Oslo added, "The fact that Saturn also has a dilute core strengthens the idea that these structures are not the result of rare, extremely high-energy impacts but instead form gradually during the long process of planetary growth and evolution."
The study also offers insights into the interiors of the many Jupiter- and Saturn-sized exoplanets now being discovered, suggesting that complex cores may be common among gas giants.
Co-author Dr Jacob Kegerreis concluded, "Giant impacts are a key part of many planets' histories, but they can't explain everything! This project also accelerated another step in our development of new ways to simulate these cataclysmic events in ever greater detail, helping us to continue narrowing down how the amazing diversity of worlds we see in the Solar System and beyond came to be."
Research Report:No dilute core produced in simulations of giant impacts on to Jupiter
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