A Moon in Our Solar System Might Be Going Off Like a Shaken Soda Can

Hoboken, N.J., July 18, 2024 – Enceladus, the sixth-largest of Saturn’s moons, is known for its remarkable cryovolcanoes—vast geysers, spurting from cracks in the moon’s frigid shell, that blast jets of water and ice right out into space. The jets, which form a plume feeding one of Saturn’s many rings, represent a tantalizing challenge to researchers, who believe the subsurface ocean from which they originate might have the potential to sustain extraterrestrial life.

Before figuring out whether that’s the case, however, researchers first need to understand what, exactly, is powering Enceladus’s cryovolcanoes. The traditional explanation is that the low pressure in space causes water to boil, even when it's cold, forcing the plumes out like steam from a kettle-spout.the low pressure in space causes water to boil, even when it's cold, forcing the plumes out like steam from a kettle-spout. Now, though, a collaboration between researchers at Stevens Institute of Technology and NASA’s Jet Propulsion Laboratory (JPL), offers a new explanation: the geysers could be powered by the sudden expansion of dissolved gasses as they escape through fissures in the moon’s surface.

“This is essentially the same mechanism that causes a shaken-up can of soda to explode when you pop it open—just on a much bigger scale,” explains Jason Rabinovitch, the study’s joint lead author and an assistant professor at Stevens Institute of Technology. “It’s also very similar to the processes that cause some volcanoes here on Earth to erupt—except, of course, with water instead of magma.”
 
If the theory is correct, Rabinovitch adds, then Enceladus’s plume starts to look even more interesting. Water sheds many of its impurities when it’s boiled into steam, so an eruption driven by boiling water may not transport everything that exists in the ocean into space—but an eruption powered by dissolved gasses could be able to carry more interesting molecules into space. “If that’s the case, then by sampling the jets we could potentially learn a great deal about what’s going on beneath the moon’s surface,” he explains.

It’s possible that a combination of effects, including pressure and heat, are driving Enceladus’s cryovolcanoes—but even so, the new theory is an important addition to our understanding of Enceladus, adds Karl Mitchell, the study’s joint first author and a planetary scientist at JPL. “If found to be true, this is a really energetic process that would easily transport ocean contents into space, including possible signs of life, which is potentially good news for future missions studying Enceladus,” he says.

In fact, research from the Cassini space probe, which first discovered Enceladus’s cryovolcanoes, and flew through a plume in 2015, shows that the geysers contain not just water vapor, but also volatile gasses, salts, organic compounds, and carbon dioxide. That’s much easier to explain if dissolved gasses are helping to propel the plume upward, the team says.

“This model takes a new, crucial step forward in how well we can reproduce what's actually happening as things move from the subsurface ocean through the ice conduit and into space,” said Dr. Morgan Cable, a co-author and research scientist at JPL. “This means we can better interpret current and future measurements of the plume, in particular those concerning the habitability and possible astrobiological potential of the ocean.”

Using computer simulations to model cryovolcanoes powered by dissolved gasses including methane and hydrogen, the research team was able to model the way that material from the ocean would enter the plume.Much of that material would likely escape the moon’s gravitational pull and wind up in space. Necessarily, however, that involved some educated guesswork about the makeup of Enceladus’s hidden ocean, and the geometry of the fissures that give rise to the cryovolcanoes.

“We don’t know yet if our models are correct—there’s still a huge amount to learn, and there’s a limit to how much we can find out from down here on Earth,” Dr. Rabinovitch said. “Still, studies like these will be vital as we prepare to send future missions to Enceladus. Understanding how the plume operates will be crucial as we plan experiments and interpret data, and begin to figure out what’s really going on beneath the moon’s surface.”

About Stevens Institute of Technology
Stevens Institute of Technology is a premier, private research university situated in Hoboken, New Jersey. Since our founding in 1870, technological innovation has been the hallmark of Stevens’ education and research. Within the university’s three schools and one college, 8,000 undergraduate and graduate students collaborate closely with faculty in an interdisciplinary, student-centric, entrepreneurial environment. Academic and research programs spanning business, computing, engineering, the arts and other disciplines actively advance the frontiers of science and leverage technology to confront our most pressing global challenges. The university continues to be consistently ranked among the nation’s leaders in career services, post-graduation salaries of alumni and return on tuition investment.

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