Saturn’s icy moon Enceladus has long fascinated scientists due to its dramatic geysers, which blast plumes of water vapor, ice, and organic molecules into space. These eruptions, first detected by NASA’s Cassini spacecraft, hinted at a hidden subsurface ocean, raising hopes that Enceladus could be one of the most promising locations for alien life. Now, a new study challenges this assumption, suggesting that the geysers may originate from a mushy zone of briny ice, rather than directly from the ocean beneath the ice shell. If true, this could change how scientists assess the habitability of Enceladus—and other icy moons across the solar system.
A surprising new theory behind Enceladus’ geysers
A recent study published in Geophysical Research Letters presents a new model for how Enceladus’ geysers form. Led by Professor Colin R. Meyer of Dartmouth College, the research suggests that instead of water erupting directly from a deep ocean, the geysers may result from shear heating, a process where friction between moving ice layers generates enough heat to melt briny pockets within the crust.
“The Cassini spacecraft flew through one of Enceladus’s plumes and measured organics, a possible sign of life, making these geysers unique and important to astrobiology,” Meyer explains. “This plume material emanates from a potentially habitable ocean below the ice shell, so we want to understand how the geysers form to determine if Enceladus is habitable.”
The study proposes that tidal forces from Saturn cause stress on the moon’s ice shell, resulting in localized melting that forms a “mushy zone” of partially melted ice and liquid brine. This brine then escapes through fractures, creating the towering plumes observed by Cassini.
How Enceladus’ ice shell could be shaping the plumes
Previous models suggested that Enceladus’ plumes were directly connected to its global subsurface ocean, meaning that anything erupting into space would have originated deep below the surface. However, Meyer’s research identifies two major weaknesses in this theory:
- Fracture stability – Scientists have struggled to explain how cracks could remain open through Enceladus’ thick ice shell, allowing ocean water to escape continuously.
- Transport mechanism – There is no clear explanation for how ocean water could travel through the fractures to the surface without freezing or clogging the passage.
Instead, Meyer’s team suggests that the moon’s icy crust is melting from within as a result of tidal stress, forming pockets of briny liquid. “Tidal forces from Saturn pull on Enceladus, creating stress that deforms the ice shell,” Meyer explains. “This stress causes the ice to rub against itself, generating heat and melting the brine trapped inside.”
The briny mixture lowers the melting point of the ice, allowing for localized melting that feeds the plumes—without requiring a direct connection to the deep ocean.
Could Enceladus still support life?
Despite this new interpretation of the geysers, Enceladus remains a prime candidate for extraterrestrial life. Cassini’s data revealed that the plumes contain water vapor, carbon dioxide, methane, ammonia, nitrogen, salts, and silica—all ingredients essential for life as we know it.
“In the latter case, the fractures become an important conduit for life,” Meyer says, explaining how briny pockets within the ice could still exchange material with the deeper ocean. This means that even if the plumes don’t originate directly from the ocean, they could still transport organic molecules and potential biosignatures to the surface.
