A colossal impact may not have created the interior of the giant planet after all.
This artist’s conception illustrates the previous theory of a planet colliding with Jupiter’s core, triggering shock waves and turbulent mixing.
Credit: Thomas Sandnes
- Recent research utilizing advanced supercomputer simulations challenges the prevailing hypothesis that a giant impact formed Jupiter’s dilute core.
- These simulations, incorporating a novel mixing method, consistently failed to reproduce a dilute core structure, even under extreme impact conditions; instead, a distinct core-mantle boundary formed.
- The study suggests that Jupiter’s dilute core, and potentially Saturn’s, likely resulted from the gradual accretion and mixing of light and heavy materials during planetary formation and evolution, not a singular catastrophic event.
- The findings have implications for understanding the internal structures of Jupiter- and Saturn-sized exoplanets, suggesting that dilute cores may be a common feature rather than a result of rare, high-energy impacts.
New research suggests a giant impact may not have been responsible for the formation of Jupiter’s core. Most planetary scientists thought that a colossal collision with an early planet containing half of Jupiter’s core material could have mixed up the central region of the gas giant enough to explain its interior today.
But a new study published in “Monthly Notices of the Royal Astronomical Society” suggests its make-up was actually caused by how the growing planet absorbed heavy and light materials as it formed and evolved.
Unlike what scientists once expected, Jupiter’s core doesn’t have a sharp boundary but instead gradually blends into the surrounding layers of mostly hydrogen — a structure known as a dilute core. How this dilute core formed has been a key question among scientists and astronomers ever since NASA’s Juno spacecraft first revealed its existence.
Using cutting-edge supercomputer simulations of planetary impacts, with a new method to improve the simulation’s treatment of mixing between materials, researchers from Durham University, in collaboration with scientists from NASA, SETI, and CENSSS, University of Oslo, tested whether a massive collision could have created Jupiter’s dilute core.
The study found that no stable dilute core structure was produced in any of the simulations, even in those involving impacts under extreme conditions. Instead, the simulations demonstrate that the dense rock and ice core material displaced by an impact would quickly re-settle, leaving a distinct boundary with the outer layers of hydrogen and helium, rather than forming a smooth transition zone between the two regions.
Reflecting on the findings, lead author of the study 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.”
Jupiter isn’t the only planet with a dilute core. Scientists have recently found evidence that Saturn has one, too. Luis Teodoro of the University of Oslo said, “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 findings of this study could also help inform scientists’ understanding and interpretation of the many Jupiter- and Saturn-sized exoplanets that have been observed around distant stars. If dilute cores aren’t made by rare and extreme impacts, then perhaps most or all of these planets have comparably complex interiors.
Co-author of the study Jacob Kegerreis said, “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.”
