New simulations using supercomputers have shown that Enceladus, a moon of Saturn, loses 20 to 40 percent less mass from its icy plumes than previously estimated. Researchers at the University of Texas at Austin analyzed data from NASA's Cassini mission to model the plumes' behavior. These findings could inform future missions probing the moon's subsurface ocean for signs of life.
Enceladus, one of Saturn's icy moons, has captivated scientists since NASA's Cassini-Huygens mission began observing it in 2005. The spacecraft captured images of towering geysers erupting from the moon's surface, ejecting water vapor and ice particles into space and forming a faint ring around Saturn.
A recent study, published in August 2025 in the Journal of Geophysical Research: Planets, used advanced Direct Simulation Monte Carlo (DSMC) models to analyze these plumes. Led by Arnaud Mahieux, a senior researcher at the Royal Belgian Institute for Space Aeronomy and affiliate of the University of Texas at Austin's Department of Aerospace Engineering & Engineering Mechanics, the research was conducted at the Texas Advanced Computing Center (TACC).
"The mass flow rates from Enceladus are between 20 to 40 percent lower than what you find in the scientific literature," Mahieux said. The team built on their 2019 work, which first applied DSMC techniques to determine plume starting conditions like vent sizes, vapor-to-ice ratios, temperatures, and escape speeds. Using TACC's Lonestar6 and Stampede3 supercomputers, they simulated conditions for 100 cryovolcanic sources.
"DSMC simulations are very expensive," Mahieux noted. "We used TACC supercomputers back in 2015 to obtain the parameterizations to reduce computation time from 48 hours then to just a few milliseconds now." The models, incorporating the DSMC code 'Planet' developed by co-author David Goldstein in 2011, accurately captured the low-gravity environment of Enceladus, which is only 313 miles wide. They tracked millions of molecules over microsecond time steps, revealing plume densities, speeds, and exit temperatures.
"The main finding of our new study is that for 100 cryovolcanic sources, we could constrain the mass flow rates and other parameters that were not derived before, such as the temperature at which the material was exiting. This is a big step forward in understanding what's happening on Enceladus," Mahieux added.
Enceladus's plumes provide a window into its subsurface liquid ocean, potentially habitable like those on other outer solar system moons. By sampling material from deep below the ice crust, scientists can study ocean conditions indirectly. Future NASA and ESA missions may land on the surface and drill to the ocean, seeking chemical signs of life. As Mahieux concluded, "Supercomputers can give us answers to questions we couldn't dream of asking even 10 or 15 years ago."