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Titan, the largest moon of Saturn, is the only other world in the Solar System where there's liquid flowing freely on the surface. But it's not water like on Earth, it's liquid hydrocarbons, mostly methane and ethane. It rains down onto the moon and forms rivers, lakes, and seas. Researchers have now measured the depth of one of the estuaries flowing into Titan’s biggest sea and from that, they were able to estimate how deep the sea likely is.
In a paper published in the Journal of Geophysical Research, the planetary scientists have estimated the depth of Moray Sinus, which is located at the northern end of Kraken Mare, the largest known body of liquid on Titan's surface. The Cassini mission that studied Saturn and its moon for over a decade was equipped with a RADAR altimeter. The team used the time difference from return signals reflected by the surface of the sea at the estuary and signals that went through the liquid and reflected off the sea-bed to work out the depths of the estuary and the sea.
The team was able to estimate that the estuary is about 85 meters (280 feet) deep, although there is significant uncertainty that could make it either a bit shallower or much deeper. Despite the uncertainties, the data has allowed the researchers to estimate that the Kraken Sea is at least 100 meters (330 feet) deep but could easily be three times that, at around 300 meters (1,000 feet).
"The depth and composition of each of Titan's seas had already been measured, except for Titan's largest sea, Kraken Mare—which not only has a great name, but also contains about 80% of the moon's surface liquids," lead author Valerio Poggiali, a research associate at the Cornell Center for Astrophysics and Planetary Science, said in a statement.
Given this estimate, it appears that Kraken Mare is not much different from the other major liquid bodies on the surface of the moon, and this is an important fact in our understanding of Titan. Chemically, the methane in Titan’s atmosphere is converted into ethane by sunlight. So, after billions of years, it should be all ethane, but the methane persists – and its source is currently a mystery.
Further exploration of the moon is planned for mid-2026 with NASA’s Dragonfly mission aiming to look for either origins or signs of life, arriving by 2034. There has also been discussions of whether a robotic submarine could explore its sea and lakes in a future mission, something the researchers think will be vital for exploring Kraken Mare.
"Thanks to our measurements," Poggiali said, "scientists can now infer the density of the liquid with higher precision, and consequently better calibrate the sonar aboard the vessel and understand the sea's directional flows."
