Albert McKeon

Jul 16th 2021

A Lake on Saturn’s Moon Titan Is More Than a Sea Monster


Scientists at Cornell University recently estimated that the largest sea on Saturn’s moon Titan reaches a depth of at least 1,000 feet, according to the Cornell Chronicle — but don’t pack your diving gear just yet.

Not that humans will travel to the sixth planet in the solar system anytime soon, but whenever we do take the 886-million-mile journey to Saturn (give or take several million miles depending on planetary positioning), we’ll find that Titan’s idea of an ocean is nothing like the ones found on Earth. This deep sea is made up of liquid methane — not exactly an ideal setting for swimming, surfing or scuba diving.

It is conducive to exploration, though. In 2026, NASA plans to send a drone named Dragonfly to Titan, as points out, and there’s talk of a submarine exploring the underwater reaches of the ocean. Until then, what is already known about this big sea is helping scientists understand Titan’s landscape. By learning about the ocean’s depth and makeup, they’re getting an idea of the moon’s hydrological system and any possible connection to Earth.

A Moon With Earthly Water

With the recent assessment of Titan’s biggest ocean, Kraken Mare, there’s no doubt it indeed lives up to its monstrous name. But unlike the sea monsters of Norse fables, this sea is real and observable to spacecraft. It’s nearly the size of all five Great Lakes combined, as the Cornell Chronicle notes. That’s how we are aware of its size. NASA’s Cassini probe observed Saturn and its moons for 13 years before exhausting its fuel supply in 2017 and taking a final plunge into the planet’s atmosphere.

During its 294 orbits of Saturn, it took more than 450,000 photographs, many of them breathtaking images of a world that is, as NASA puts it, “ruled by raging storms and delicate harmonies of gravity.” Cassini revealed “astounding worlds where methane rivers run to a methane sea and where jets of ice and gas are blasting material into space from a liquid water ocean that might harbor the ingredients for life,” they continue.

Outside of satisfying curiosity about Saturn’s many rings, Cassini also explored the planet’s icy moons. Scientists have long thought the moons offered conditions suitable to life, and that’s why a close study of Titan captures attention. Titan is described as Earth-like because it is the only moon in our solar system that has a dense atmosphere and clouds, and it is the only moon with liquids in the form of rivers, lakes and oceans on its surface.

NASA points out that Titan, the largest of Saturn’s 82 moons, has an atmosphere composed mostly of nitrogen, just like Earth. However, Titan’s surface pressure is 50% higher than our planet’s. Its subsurface waters are of particular interest to scientists because they could contain forms of life with chemical compositions possibly unlike those found on Earth.

No Ordinary Measuring Stick

The search for life beyond Earth — a quest that drives NASA’s Mars Exploration Program, as well as many other current and future space missions — is why the recent calculation about the depth of Titan’s deepest ocean has significance. The more we learn about the building blocks of the planets and moons in our neighborhood, the more we understand how life on Earth came to be.

Analyzing data gathered by a radar altimeter on Cassini as it flew 600 miles above Titan’s surface in 2014, scientists and engineers from NASA’s Jet Propulsion Laboratory were able to gauge the depth of Moray Sinus (an estuary at the north end of Kraken Mare) to be about 280 feet deep, the Cornell Chronicle reports. The estuary is shallower than the depths of the center of Kraken Mare, but the ocean itself was too deep for Cassini’s radar to measure.

So, the scientists and engineers devised a workaround. They discerned the depth of Kraken Mare by noting the radar’s return time differences on the liquid surface and sea bottom, and they identified the sea’s composition by the amount of radar energy absorbed during transit through the liquid. That’s how they determined the depth of Kraken Mare to be at least 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,” Valerio Poggiali, a research associate at the Cornell Center for Astrophysics and Planetary Science (CCAPS), told the Cornell Chronicle.

There’s More Lake to Explore

Scientists previously believed methane would dominate Kraken Mare because of its size and extension to the moon’s lower latitudes. But the study of Cassini’s data showed that the ocean’s liquid methane composition is not much different from other northern seas on Titan.

This finding excites scientists. As Poggiali told the Cornell Chronicle, Saturn’s moon Titan represents a model environment of a possible atmosphere of early Earth. Knowing Kraken Mare has an abundance of liquid methane will only help to assess models of Titan’s Earth-like hydrologic system, he said.

As the New York Times observed, these findings represent more than complicated science. According to their reporting, Poggiali thinks of Titan partly as “a laboratory where, over millions of years, chemistry could have learned how to generate energy and store information.” That has meaning for us Earthlings, and it’s what makes the plan to send Dragonfly and a 20-foot-long submarine to closely examine Kraken Mare from below tantalizing.

“These are processes that have happened on our planet too, but they left no traces,” Poggiali told the Times. “As you probably see, we need to get back to Titan to better understand the mystery of life.”

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