Titan, Saturn's moon, has beaches that appear to be shaped by waves

During its T85 Titan flyby on July 24, 2012, the Cassini spacecraft recorded an unexpectedly bright reflection on the surface of Lake Kivu Lakos. Visible and Infrared Mapping Spectrometer (VIMS) data were interpreted as roughness in the methane and ethane lake, which could be a sign of mudflats, surface bubbles, or waves.

“Our models of landscape evolution show that coastlines on Titan are most consistent with terrestrial lakes that have been eroded by waves,” says Rose Palermo, a coastal geomorphologist at the Center for Coastal and Marine Sciences in St. Petersburg, who led the study looking at wave signatures. Corrosion on Titan. The evidence for waves is still inconclusive, but future manned missions to Titan will likely pack some surfboards just in case.

Troubled seas

While waves were considered The most logical explanation As for the reflections visible in Cassini's VIMS images for some time, other studies aiming to confirm their existence have found no wave activity at all. “Other observations show that liquid surfaces were very static in the past, very flat,” Palermo says. “A possible explanation for this is that at the time we were observing Titan, the winds were very low, so there were not many waves at that time. To confirm the waves, we would need better resolution data,” she adds.

The problem is that this high-resolution data won't reach us anytime soon. The next Dragonfly mission isn't supposed to arrive at Titan before 2034, even if all goes as planned.

To get a better idea of ​​possible waves on Titan a little sooner, the Palermo team went on to infer their presence from indirect signals. The researchers hypothesized that coastlines on Titan could be formed by one of three candidate scenarios. They initially assumed there was no corrosion at all; The second typical uniform erosion is caused by the decomposition of bedrock by liquid ethane and methane; The third assumes erosion due to wave activity. “We took random river topography, and filled in flooded river valleys all around the lake. We then used a computer model of landscape evolution to erode the coastline to 50 percent of its original size.”

Wave sizing

Palermo simulations showed that wave erosion gave rise to coastal shapes that closely matched those actually observed on Titan.

The team validated its model using data from closer to home. “We compared using the same statistical analysis to lakes on Earth, where we know what erosion processes are. With greater than 77.5% certainty, we were able to predict those known processes with our models.

But even the study that claimed there were visible waves in Cassini's VIMS images concluded that they were only about 2 cm high at best. So, even if there were waves on Titan, the question is how high and strong would they be?

According to Palermo, the wave-generating mechanisms on Titan should work just as they do on Earth, with some notable differences. “There is a difference in viscosity between water on Earth and liquid methane and ethane on Titan compared to the atmosphere,” Palermo says. Gravity is also much weaker, at only one-seventh that on Earth. “Gravity, combined with differences in material properties, contributes to waves being longer and steeper than those on land and with the same wind speed,” Palermo says.

But even with these boosts in size and power, could the waves on Titan be good for surfing?

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“There are certainly a lot of open questions that our work leads to. What is the direction of the dominant waves? Knowing that can tell us about the winds, and thus about the climate on Titan. How big are the waves? In the future, perhaps we can find out by modeling how much erosion they It occurs in one part of the lake versus another in the estimated time periods. “There is a lot we can learn in terms of surfing,” she said, “assuming the minimum wave height to surf around.” 15 cmSurfing on Titan is likely possible.

The main limit to the size and strength of any waves on Titan is that most of its seas are roughly the size of the Great Lakes in the United States. The largest, the kraken, is roughly the size of the Caspian Sea on Earth. There is no such thing as a global ocean on Titan, meaning that fetch, the distance over which winds can blow and waves can grow, is limited to tens of kilometers rather than the more than 1,500 kilometers on Earth. “However, some models show that waves on Titan are up to 1 meter high. I would say it is a surfable wave,” Palermo concluded.