TitanSaturn’s largest moon, is the only other planetary object in the solar system (other than Earth) that currently hosts rivers, lakes and seas active, although not water. They are believed to be full of liquid methane and ethanewhich flow through systems as large as the Great Lakes of North America.
The existence of these river, lake and marine environments on Titan was confirmed in 2007 with images captured by the probe cassini from NASA. With these and other data obtained remotely, scientists have studied what the mysterious liquid environment of the moon may be like, and one of the big questions is the existence of surf.
Titan’s seas and lakes are believed to be filled with liquid methane and ethane, flowing through systems as large as Earth’s Great Lakes.
Now, geologists at the Massachusetts Institute of Technology (M.I.T.) and the United States Geological Survey (USGS) have analyzed the coasts of Titan and have shown, through simulations, that it is likely that the large lakes and seas of this moon have been modeled by waves. The results are published in the journal Science Advances.
This infrared mosaic captured by the Cassini spacecraft shows the Sun shining in the seas north of Titan. / NASA/JPL-Caltech/University of Arizona/University of Idaho
The authors have first modeled the ways in which a lake can erode on Earth. They then applied their models to Titan’s seas to determine what form of erosion could have produced its coastlines. The waves They turned out to be the most likely explanation, although direct observations would be necessary to definitively confirm it.
The models indicate that waves are the most likely explanation for the shape seen on the coast of Titan
Its presence has been a controversial topic since Cassini spotted the liquid masses on this moon. “Some considered that there were no waves and that these seas are smooth as a mirror,” explains the first author, Rose Palermoa USGS geologist, “but others said they did see some roughness in the liquid surface, although they were not sure if the waves caused it.”
“The waves of Titan’s methane and ethane seas should be higher and more pronounced than those on Earth due to the difference in gravity and liquid and atmospheric conditions,” Palermo explains to SINC, “but other authors have modeled waves of up to one meter high. Currently, a student in the MIT Geomorphology group is investigating the possible properties of waves on Titan, so we will know more soon!
In any case, “based on our results, we can say that if the coasts of Titan’s seas have eroded, waves are the most likely culprit,” says another of the authors, Taylor Perron, professor of Earth, Atmospheric and Planetary Sciences at MIT. “If we could stand on the edge of one of Titan’s seas,” he speculates, “we could see them washing the shore and crashing into the coasts during storms. And they would be able to erode the material that the coast is made of.”
If we could stand at the edge of one of Titan’s seas, we would see waves of liquid methane and ethane washing ashore and crashing onto the shores during storms.
Taylor Perron (MIT)
Three possible scenarios
Titan’s seas and lakes are thought to have formed when rising levels of liquid flooded a landscape crisscrossed by river valleys. The researchers analyzed the shape of the coasts and proposed three possible scenarios: absence of coastal erosion, erosion caused by waves and one ‘uniform erosion’ caused by dissolution, where the liquid passively dissolves the shore material, or by a mechanism in which the shore gradually detaches under its own weight.
The authors simulated how the different shoreline shapes would evolve in each of the three scenarios. In the case of erosion caused by waves, they took into account a variable known as “fetch”, which describes the physical distance between a point on the shore and its opposite point on the lake or sea. A higher value indicates more space over which the wind can blow and waves can grow.
“We use the fetch as a strength indicator relative metric of waves along the coasts, being stronger in the open parts of the coast and weaker in the protected parts,” says Palermo, “but since we use these relative metrics, our results do not shed light on which ones should be their heights, but that spatial differences in erosion can be mapped and measured.”
The geologist details the results: “If the waves behave as we expect them to on Titan, our data suggest that its seas have been eroded with a probability of 77-100% by the waves, with 4-12% by a process uniform, and with a 0-11% probability without coastal erosion.”
Titan’s seas have been eroded by waves with a probability between 77 and 100%
Rose Palermo (USGS)
The team verified their results by comparing their simulations with real lakes on Earth, including those eroded by waves and those affected uniformly, such as the dissolution of limestone cliffs.
Comparison with water masses on Earth
Specifically, they focused on four of Titan’s largest and best-charted seas: Kraken Marecomparable in size to the Caspian Sea (Eurasia); Ligeia Marelarger than Lake Superior in North America; Punga Mare, longer than Lake Victoria (Africa); and Ontario Lacuswhich is 20% the size of its terrestrial namesake between Canada and the US.
Ligeia Mare of Titan. / NASA/JPL-Caltech/ASI/Cornell
The team mapped the coastlines of each sea on the moon using Cassini radar images and applied their modeling to see which erosion mechanism best explained their shape. Thus they verified that the four seas fit perfectly with one wave driven erosion.
Researchers are now working to determine the strength and direction of the winds of Titan that can raise the waves with which its coasts are eroded. They would also like a future spacecraft to be able to directly see or confirm the waves on that world.
Mission to Titan but not to its seas
“The next mission to Titan is Dragonfly (which will operate a helicopter on the surface of the moon), but, unfortunately for us, it will not go to lakes or seas,” Palermo laments. “Currently there is no other plan that can confirm the presence of waves,” he acknowledges, “but it could be done with higher resolution images collected by a future orbiter, or with data on site, which could be picked up by a probe. So maybe one day we will know.”
The geologist concludes with a reflection applied to our own planet: “Titan presents this completely virgin systemwhich can help us to understand fundamental aspects of how coasts erode without the influence of people, and perhaps that would favor better management of our coasts on Earth.”
Illustration of Dragonfly flying over the Titan dunes. / NASA/Johns Hopkins APL/Steve Gribben
Reference:
Rose Palermo et al. “Signatures of wave erosion in Titan’s coasts.” Science Advances2024
