ScienceDaily (Apr. 5, 2004) — ESA could be releasing its own marine weather report next January - but not for any Earthly ocean. Thanks to the NASA/ESA Cassini/Huygens mission, the first data about an extraterrestrial ocean may finally be received, ending 25 years of scientific speculation.

There is a growing body of evidence that at least part of Titan’s surface is covered with liquid methane and a related chemical, ethane. On Earth, methane is a gas but at the colder temperatures of Titan, around –180 °C, it could exist as a liquid or be frozen solid into ice. If it is a liquid, it could exist as lakes in craters or even as vast oceans. Recent radar observations suggest that up to seventy-five percent of the surface may be covered in liquid. In that case, it is highly likely that after its descent through Titan’s atmosphere, the Huygens probe will not so much land as ‘splashdown’.

To understand what to expect if this happens, the Principal Investigator of the Huygens Surface Science Package, John Zarnecki of the UK’s Open University, has teamed up with Nadeem Ghafoor, Surrey Satellite Technology, and colleagues from the Southampton Oceanography Centre.

Together, the team used a computer model to predict the behaviour of the ocean on Titan. They looked at the waves they might encounter. On Earth, wind drives the waves. By placing Titan’s characteristics into their computer program, the team discovered that Titan’s waves will be slow-motion giants, reaching some seven times the height of a typical wave on Earth. Their height is mostly generated because Titan’s gravitational strength is only one seventh that of Earth.

If Huygens does land on an ocean, the Surface Science Package will attempt to measure its composition, and depth using sonar. It will also record the frequency and height of any waves that pass.

Extreme sports fans might find surfing on these waves a wild ride, according to Nadeem Ghafoor, because the waves would look seven times bigger but move three times more slowly than those on Earth.

Of course, the sea would be 180 degrees below zero and it would not smell very good either. The surroundings would be a murky orange-brown because of the permanently overcast conditions and there might be the occasional iceberg to dodge near the shore!

In short, Titan could be like nothing like we have seen before and Cassini/Huygens is due to reveal all on 14 January 2005.

This narrow angle field-of-view artist's rendering shows Titan's surface with Saturn dimly in the background through Titan's thick atmosphere of methane, ethane and (mostly) nitrogen. The Cassini spacecraft flys over the surface with its high-gain antenna pointed at the Huygens probe as it reaches the surface. Thin methane clouds dot the horizon, and a narrow methane spring or 'methanefall' flows from the cliff at left and drifts mostly into vapour. Smooth ice features rise out of the methane/ethane lake, and crater walls can be seen far in the distance. (Credit: David Seal / Courtesy of European Space Agency)

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