Titan makes waves: Lake and sea shores on Saturn’s moon could be from wave erosion

Simulations suggest that the coastlines of lakes and seas on the surface of Saturn’s largest moon Titan might have been formed by erosion.

This adds credence to the suggestion that Titan’s liquid bodies have waves.

Titan is the only other planetary body in the solar system which currently has active rivers, lakes and seas. The existence of lakes and larger seas – some as big as the Great Lakes on Earth – was confirmed in images taken by NASA’s Cassini spacecraft in 2007.

Grey grainy image of lake on titan
Lake on Titan captured by Cassini in 2007, Credit: NASA/JPL-Caltech/ASI.

With an average temperature of about -179°C Titan can’t sustain liquid water. The rivers, lakes and seas are likely made of methane and ethane.

Previous research has suggested wave activity on Titan based on remote images. But the results of past observations have sparked debate.

A new approach to investigate the presence of waves on Titan is detailed in a paper published in Science Advances.

Researchers at the Massachusetts Institute of Technology (MIT) first modelled how lakeshores are produced on Earth. Applying this to Titan, the team was able to determine what kind of erosion produced the shorelines observed by Cassini.

The culprit: waves.

But direct observations of waves on Titan remains elusive.

“We can say, based on our results, that if the coastlines of Titan’s seas have eroded, waves are the most likely culprit,” says senior author Taylor Perron. “If we could stand at the edge of one of Titan’s seas, we might see waves of liquid methane and ethane lapping on the shore and crashing on the coasts during storms. And they would be capable of eroding the material that the coast is made of.”

Conflicting views have emerged about the presence of waves on Titan in the past.

“Some people who tried to see evidence for waves didn’t see any, and said, ‘These seas are mirror-smooth,’” says first author Rose Palermo. “Others said they did see some roughness on the liquid surface but weren’t sure if waves caused it.”

The MIT research provides a strong link between waves and the shapes of the lakes seen on Titan.

“We had the same starting shorelines, and we saw that you get a really different final shape under uniform erosion versus wave erosion,” explains Perron. “They all kind of look like the flying spaghetti monster because of the flooded river valleys, but the two types of erosion produce very different endpoints.”

“We found that if the coastlines have eroded, their shapes are more consistent with erosion by waves than by uniform erosion or no erosion at all,” Perron says.

The next step is to determine how strong and in which direction Titan’s winds must be blowing to whip up the waves chipping away at the coasts.

“Titan presents this case of a completely untouched system,” Palermo says. “It could help us learn more fundamental things about how coasts erode without the influence of people, and maybe that can help us better manage our coastlines on Earth in the future.”

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