Titan’s Largest Methane Lake May Be One Thousand Feet Deep

NASA’s Cassini probe flew just 600 miles above Saturn’s largest moon to gather the data

A map of Saturn's moon, Titan, shows the lakes of its northern hemisphere
Titan's largest lake, Kraken Mare, is larger than the five Great Lakes combined. NASA/JPL-Caltech/ASI/USGS

When NASA’s Cassini probe flew just above Saturn’s largest moon Titan while shooting radar at its surface, it was gathering data about the depth of the lakes across the moon’s surface. To figure out a lake's depth, in theory, Cassini could measure when the radar hit the surface of the lake and then bounced off the bottom and reflected back to the probe. But when Cassini attempted this at Titan’s largest lake, its radar never reached the bottom, George Dvorsky reports for Gizmodo.

The lake, called Kraken Mare, was either too deep or too absorptive for the radar to reach the lakebed. But by analyzing the data that Cassini gathered from shallower bodies of liquid, including a nearby estuary called Moray Sinus, researchers at Cornell University were able to tease out the lake’s depth. According to a paper published in JGR Planets, Kraken Mare is at least 330 feet deep and may be as much as 1,000 feet deep. The information that the team gathered about the lake’s chemical makeup may help an upcoming NASA mission that aims to explore the lake with a robotic submarine.

“[Kraken Mare] not only has a great name, but also contains about 80% of the moon’s surface liquids,” says co-author Valerio Poggiali, a planetary scientist at Cornell University, in a statement. “In this context to understand the depth and composition of Kraken Mare and the Moray Sinus is important because this enables a more precise assessment on Titan’s methane hydrology. Still, we have to solve many mysteries.”

Titan is about two and a half times smaller than Earth and it’s one of the only moons in the solar system with a substantial atmosphere, which is 98 percent nitrogen and two percent methane, Jamie Carter reports for Forbes. That also means it has impressive landscapes shaped by weather and rainstorms. But Titan’s lakes aren’t filled with water: Instead, they’re full of oily ethane and methane, like liquified natural gas, per Gizmodo.

The lakes have caught scientists’ attention because they are a strong contender for housing life beyond Earth. Kraken Mare covers more area than all five of North America’s Great Lakes combined.

Cassini took measurements from liquid formations on the surface of Titan, including the Moray Sinus estuary at the northern end of Kraken Mare. The scientists found that Moray Sinus is about 280 feet deep, about the height of the Statue of Liberty, Elizabeth Howell reports for Live Science. The measurements taken at Moray Sinus also showed the chemical makeup of the lake: about 70 percent methane, plus a mix of nitrogen and ethane.

The two measurements taken in the main body of Kraken Mare did not return a signal from the bottom of the lake. The researchers found it unlikely that the liquid in the estuary would be much different than the chemistry in the main part of the lake, but if the lake is different and causes more absorption than the estuary, then it is at least 330 feet deep. If the lake has the same chemical makeup as the estuary, then it may be over 1,000 feet deep, Michael Irving reports for New Atlas. For comparison, Lake Superior is 1,330 feet deep at its deepest point, and Lake Michigan is 925 feet deep, according to the EPA.

Poggiali says in the statement that the research could help scientists unravel more information about how Titan’s liquid methane goes through cycles in the atmosphere and ground, like water does on Earth. And by providing information about the liquid’s density, the research could also help NASA prepare to send a robotic submarine to the large moon.