Saturn’s largest moon, Titan, may be hiding a habitable world of slushy sea ice, new research hints.
Back in 2008, NASA’s Cassini spacecraft gathered data on Titan that suggested an open ocean might lurk beneath the moon’s frozen crust. But the new analysis hints that what lies underneath is instead “slushy tunnels and pockets of meltwater,” according to the investigators.
“Instead of an open ocean like we have here on Earth, we’re probably looking at something more like Arctic sea ice or aquifers, which has implications for what type of life we might find, [and] also the availability of nutrients, energy and so on,” study co-author Baptiste Journaux, an assistant professor of Earth and space sciences at the University of Washington, said in a statement.
The “smushing” moon
The story begins with Cassini, a spacecraft that launched in 1997 and spent much of its 20 years observing Saturn and its moons. Cassini spotted the shape of Titan “stretching and smushing” as it circled Saturn, according to the authors of the new study. Back then, the researchers proposed that if Titan possessed a deep ocean, that would let the crust flex under the pull of Saturn’s gravity.
Now, the new study takes into account the timing of Titan’s flexes. The team found that the shape of Titan begins to change only about 15 hours after Saturn exerts its strongest gravitational pull in Titan’s orbit. The scientists then estimated the energy it would take for Titan’s shape to alter, which, in turn, showed more about the mysterious moon’s interior.
“Nobody was expecting very strong energy dissipation inside Titan,” lead study author Flavio Petricca, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory, said in the statement. “That was the smoking gun indicating that Titan’s interior is different from what was inferred from previous analyses.”
Historically, Titan has always been hard to observe. The planet is shrouded in a thick, orange atmosphere that’s rich in chemical compounds that may be precursors to life. Looking at the surface requires radar (which Cassini possessed, whereas predecessor flyby missions Voyager 1 and Voyager 2 did not). Cassini’s observations revealed a bizarre surface where methane falls as rain, seas constantly shift, and temperatures stand around minus 297 degrees Fahrenheit (minus 183 degrees Celsius).
Titanic slushies
So what is going on in Titan’s interior? The new study says below the frozen exterior, the moon’s innards appear to have ice, meltwater pockets and overall, a slushier environment than believed in 2008. The slush is thick and likely accounts for the observed lag in Titan’s shape shifts. While water is believed to be in the slush, it wouldn’t be as liquid as an open ocean, the team found.
Aside from recycling the old Cassini radio-wave observations, the researchers used new thermodynamic models developed by Journaux’s lab to study how water, minerals and other components behave on worlds like Titan.
“The watery layer on Titan is so thick, the pressure is so immense, that the physics of water changes,” Journaux said. “Water and ice behave in a different way than sea water here on Earth.”
Expanding the search for life
While at first this lack of a full ocean sounds like a blow to the search for life, the research team emphasized that instead, “It expands the range of environments we might consider habitable,” Jones said.
Scientists also found that “pockets of fresh water” may exist within Titan at life-friendly temperatures of 68 degrees Fahrenheit (20 degrees Celsius). Moreover, nutrients would be concentrated in small pools of this water, perhaps allowing for more rich conditions for life than a less-concentrated ocean would.
Upcoming observations may aid our understanding of Titan. NASA’s Dragonfly mission is set to launch as soon as 2028, and it should arrive at Titan in 2034. It will be the second flying vehicle on another world besides Earth, after Ingenuity, a helicopter on Mars. It is hoped that Dragonfly’s surface observations of Titan will reveal more about where life may be lurking and how much water might be available for organisms.
