Saturn’s largest moon Titan is the one place aside from Earth known to have an environment and liquids in the shape of rivers, lakes and seas on its surface. Due to its extremely cold temperature, the liquids on Titan are fabricated from hydrocarbons like methane and ethane, and the surface is fabricated from solid water ice. A brand new study, led by planetary scientists on the University of Hawai’i at Manoa, revealed that methane gas can also be trapped throughout the ice, forming a definite crust as much as six miles thick, which warms the underlying ice shell and can also explain Titan’s methane-rich atmosphere.
The research team, led by research associate Lauren Schurmeier, that also includes Gwendolyn Brouwer, doctoral candidate, and Sarah Fagents, associate director and researcher, within the Hawai’i Institute of Geophysics and Planetology (HIGP) within the UH Manoa School of Ocean and Earth Science and Technology (SOEST), observed in NASA data that Titan’s impact craters are a whole bunch of meters shallower than expected and only 90 craters have been identified on this moon.
“This was very surprising because, based on other moons, we expect to see many more impact craters on the surface and craters which are much deeper than what we observe on Titan,” said Schurmeier. “We realized something unique to Titan should be making them grow to be shallower and disappear relatively quickly.”
To analyze what could be beneath this mystery, the researchers tested in a pc model how the topography of Titan might calm down or rebound after an impact if the ice shell was covered with a layer of insulating methane clathrate ice, a form of solid water ice with methane gas trapped throughout the crystal structure. For the reason that initial shape of Titan’s craters is unknown, the researchers modeled and compared two plausible initial depths, based on fresh-looking craters of comparable size on a similar-size icy moon, Ganymede.
“Using this modeling approach, we were in a position to constrain the methane clathrate crust thickness to 5 to 10 kilometers [about three to six miles] because simulations using that thickness produced crater depths that best matched the observed craters,” said Schurmeier. “The methane clathrate crust warms Titan’s interior and causes surprisingly rapid topographic rest, which ends up in crater shallowing at a rate that’s near that of fast-moving warm glaciers on Earth.”
Methane-rich atmosphere
Estimating the thickness of the methane ice shell is significant because it might explain the origin of Titan’s methane-rich atmosphere and helps researchers understand Titan’s carbon cycle, liquid methane-based “hydrological cycle,” and changing climate.
“Titan is a natural laboratory to check how the greenhouse gas methane warms and cycles through the atmosphere,” said Schurmeier. “Earth’s methane clathrate hydrates, present in the permafrost of Siberia and below the arctic seafloor, are currently destabilizing and releasing methane. So, lessons from Titan can provide vital insights into processes happening on Earth.”
Structure of Titan
The topography seen on Titan is smart in light of those latest findings. And constraining the thickness of the methane clathrate ice crust indicates that Titan’s interior is probably going warm — not cold, rigid, and inactive as previously thought.
“Methane clathrate is stronger and more insulating than regular water ice,” said Schurmeier. “A clathrate crust insulates Titan’s interior, makes the water ice shell very warm and ductile, and implies that Titan’s ice shell is or was slowly convecting.”
“If life exists in Titan’s ocean under the thick ice shell, any signs of life (biomarkers) would have to be transported up Titan’s ice shell to where we could more easily access or view them with future missions,” Schurmeier added. “That is more prone to occur if Titan’s ice shell is warm and convecting.”
With the NASA Dragonfly mission to Titan scheduled to launch in July 2028 and arrive in 2034, researchers could have a possibility to make up-close observations of this moon and further investigate the icy surface, including a crater named Selk.