Saturn’s moon Titan may have a 6 mile thick crust of meta ice – could there be life underneath?

Scientists have discovered that the icy shell of Saturn’s largest moon, Titan, may have an isolated, six-mile-thick (9.7-kilometer-thick) layer of methane ice beneath its surface. Ironically, this layer may make it easier to detect signs of life from Titan’s subsurface ocean. And in the future, the discovery can benefit the fight against human-driven climate change on Earth.

Titanium could be a moon, but it’s also more like it The earth than anyone else Solar system planet. This is because it is the only planet or the moon in the solar system other than Earth to have an atmosphere as well as flowing rivers, lakes and oceans. However, due to Titan’s frigid temperatures, this liquid is composed of hydrocarbons such as methane and ethane. Yet the surface ice on Titan is indeed water.

The new findings from a team of planetary scientists at the University of Hawaii at Mānoa revealed that methane gas can also be trapped in Titan’s ice shell, forming a distinct crust up to six miles thick. This gas can heat the underlying ice shell and help molecules rise to Titan’s surface, some of which could indicate the presence of life. This warming may also help to explain Titan’s methane-rich atmosphere.

“If life exists in Titan’s oceans beneath the thick ice shell, any signs of life, biomarkers, would need to be transported up Titan’s ice shell where we can more easily access or see them with future missions,” said research team leader and University of Hawaii researcher Lauren Schurmeier said in a statement. “This is more likely to occur if Titan’s ice shell is warm and connecting.”

The team was first tipped off to the potential existence of this connecting layer of methane ice by the presence of shallow impact craters on Titan. Only 90 impact craters have been seen on the surface of the Saturnian moon, and these have been confusing to observe because they bark be hundreds of feet deeper than they actually are.

“This was very surprising because, based on other moons, we would expect to see many more impact craters on the surface and craters that are much deeper than what we observe on Titan,” Schurmeier said. “We realized that something unique to Titan must cause them to become shallower and disappear relatively quickly.”

Exploring Titan’s shallow craters

To further delve into the mystery of Titan’s cool impact craters, Schurmeier and colleagues turned to computer modeling. This allowed them to test how much surface area Saturn largest moon would relax and recover from an asteroid impact if its icy shell was coated with an insulating layer of methane clathrate.

Methane clathrate, or “methane hydrate,” is a solid compound in which a large amount of methane is trapped in the crystalline structure of water, creating a solid similar to ice.

Considering craters of similar size on an icy moon Jupiter it is comparable to Titan, Ganymedethe researchers were able to compare the possible depths of impact craters on the Saturnian moon.

“Using this modeling approach, we were able to constrain the thickness of the methane clathrate crust to five to 10 kilometers (about three to six miles) because simulations at that thickness produced crater depths that best matched the observed craters,” Schurmeier added. “The methane clathrate crust heats Titan’s interior and causes surprisingly rapid topographic relaxation, resulting in crater subsidence at a rate close to that of fast-moving warm glaciers on Earth.”

Cassini images of crater-like features on Titan.

Cassini synthetic aperture radar (SAR) images of Titan’s impact craters. Arrows indicate potential forms of crater modification processes, including: dunes and sand (purple), channels (blue), and significant crater edge erosion (pink). (Image credit: NASA/Cassini)

The thickness of this icy methane shell matters because it may eventually explain why Titan’s atmosphere is particularly rich in this hydrocarbon. It could also help scientists better understand Titan’s carbon cycle, its liquid methane-based “hydrological cycle” and the changing climate of the Saturnian moon.

“Titan is a natural laboratory for studying how the greenhouse gas methane heats and circulates through the atmosphere,” explained Schurmeier. “Earth’s methane clathrate hydrates, found in the permafrost of Siberia and beneath the Arctic seafloor, are currently destabilizing and releasing methane.

“So, lessons learned from Titan can provide important insights about processes that take place on earth.”

Part of the Moon's interior with orange, light blue, dark blue and brown falling layers

Proposed diagram of Titan’s interior (not to scale), showing a methane clathrate crust over a convecting ice shell. (Image credit: Schurmeier, et al., 2024)

The thickness of the methane clathrate crust, when viewed in light of Titan’s topography, means that the Saturnian moon’s interior is likely hot and flexible rather than cold and rigid, as once thought.

“Methane clathrate is stronger and more insulating than regular water ice,” Schurmeier added. “A clathrate crust insulates Titan’s interior, making the water ice shell very hot and malleable, suggesting that Titan’s ice shell is or was slowly convecting.”

And that convection means that biomarkers suggesting that life could have been lifted from Titan’s subterranean ocean and brought to its outer icy shell, just waiting to be discovered.

This research could serve as a helpful guide to NASA scientists who intend to investigate Titan using the upcoming Dragonfly spaceship. Dragonfly will launch in 2028 and hopefully reach the Saturnian system in 2034 to make close-up observations of Titan’s icy surface.

The team’s research was published on September 30 in the The Planetary Science Journal.