NASA’s Methane Ocean Submarine

Image: NASA

Does a space submarine sound cool? Does it sound insane? The answer to both questions is a resounding yes, which makes NASA’s plans to fire one into space to explore the alien oceans of Titan all the more amazing.

Titan is the largest of Saturn’s many moons and the second largest in the solar system. But it’s not just its impressive size that has scientists eying it up through their telescopes. Oh, no. You see, Titan is the only place in our solar system, other than Earth, where we have found surface liquids.

Just like our own planet, it has rivers, lakes and even oceans. It has its own thick nitrogen-rich atmosphere and cloud system. And just like it does here on Earth, it rains. A slight difference on Titan, though, is that it rains methane.

Whilst our hydrological cycle is based on water, Titan’s is based on methane. This is because the moon is so far away from the Sun methane can exist in liquid form. During its tour of the Saturn system, the Cassini satellite revealed that 620,000 square miles (1.6 million square kilometres) of Titan’s surface was covered with these methane seas and lakes.

The presence of liquid is seen as an essential requisite for the emergence of life. And even though Titan’s oceans are formed from natural gas liquids (mainly a mixture of methane and ethane) rather than water, there is speculation that the moon could harbour some form of methane-based life. Whilst this is seen as unlikely, there is still much that could be learnt from exploring Titan’s mysterious oceans.

There is speculation that the moon could harbour some form of methane-based life

Sending a submarine on an 870 million mile (1.4 billion km) journey through space to then land on the surface of an alien moon is in itself a daunting task. But actually building an automated submersible that would be capable of exploring Titan’s noxious oceans, where temperatures can be as low as -179 Celsius (-290 Fahrenheit), presents even more unknown challenges.

In order to determine how a submarine could operate in these conditions researchers from the Washington State University (WSU) have built a miniature version of this alien ocean here on Earth. To do this, WSU built a test chamber and filled it with a very cold liquid mixture similar to that which NASA expects to find on the moon’s surface. This super-cold chamber has even been able to recreate the methane rain and snow that rolls in with Titan’s strange weather-fronts.

WSU have used this chamber to help understand the challenges NASA’s space submarine will encounter in this hostile environment. So far they have learnt that heat emissions will produce nitrogen bubbles in extremely cold hydrocarbon liquids, which will make it very difficult to manoeuvre the vessel. NASA will need to design a very responsive ballast system to overcome this, but the presence of nitrogen in the liquid is also good news. This means that lakes and oceans will freeze at lower temperatures than expected, which means the submarine will not have to contend with icebergs (and ‘Titanic in Space’ has such a good ring to it!).

NASA hope to pursue this ambitious mission within the next 20 years, and have already earmarked a 155,000 square mile (400,000 square km) ocean called Kraken Mare (named after the legendary sea monster) for exploration.


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