Space

Depths of alien ocean probed with radar in Cassini study

Depths of alien ocean probed w...
An artist's impression of a sea on Titan
An artist's impression of a sea on Titan
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An artist's impression of a sea on Titan
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An artist's impression of a sea on Titan

Saturn’s moon Titan is one of the most fascinating bodies in the solar system, not least because it’s home to huge oceans, lakes and rivers of liquid methane. Now scientists have used radar to probe the composition and depth of its largest sea, Kraken Mare, and estimated it to be at least 300 m (1,000 ft) deep.

Titan is shrouded in a cloudy atmosphere of nitrogen, making it difficult to see the surface. So NASA’s Cassini spacecraft, which orbited Saturn between 2004 and 2017, was equipped with radar to get a better look at the ground. And the resulting images revealed a surprisingly Earth-like landscape, complete with a “water” cycle made up of liquid hydrocarbons that pool in large oceans.

“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 percent of the moon’s surface liquids,” says Valerio Poggiali, lead author of the study.

In the new study, researchers from Cornell University set out to correct that oversight. They used data gathered during a 2014 Cassini flyby, when the craft used its radar altimeter to take measurements of three points within Kraken Mare.

Radar altimeters work by firing off a beam of radio waves, then measuring how long it takes them to bounce back from the ground below. Since these waves will return at different rates from liquids and solids, it can determine the depth of a body of liquid, and provide an insight into what it’s made up of.

The clearest data comes from Moray Sinus, an estuary in the northern part of Kraken Mare. Here, the team found that the sea was up to 85 m (280 ft) deep, and the absorption of the radar waves suggested it’s made up of 70 percent methane, 16 percent nitrogen and 14 percent ethane.

In the main body of Kraken Mare, however, the team could find no signal of the seafloor. That result could mean one of two things: either the liquid has a different composition and is absorbing far more of the radar waves, or it’s much deeper. The team is leaning towards the latter possibility – after all, the liquid shouldn’t be too different within the same body.

If that’s the case, the researchers estimate that Kraken Mare has to be at least 100 m (330 ft) deep, and could plunge to 300 m (1,000 ft) or more at its deepest parts. That would make it deep enough for a robotic submarine to explore, which NASA has proposed for a possible mission in 2040 or so.

Titan will no doubt attract more attention for space exploration. There’s even a chance that it might be home to non-water-based life.

The research was published in the Journal of Geophysical Research.

Source: Cornell University

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