Looking at Saturn’s largest moon

One of the first images of Titan’s surface. Photo/ESA/NASA/University of Arizona.

Director of the Australian Centre for Astrobiology at Macquarie University, Professor Malcolm Walter, says that although Saturn’s largest moon, Titan, sounds very interesting, he certainly wouldn’t want to live there.

“It’s a pretty nasty place,” says Walter. “It’s one and a half times the size of our moon, it’s absolutely frozen with a surface temperature of about –180 degrees Celsius, it probably rains oil, and has ice and sticky tar all over the surface.”

The Huygens probe – named after Titan’s discoverer, the 17th-century Dutch astronomer Christiaan Huygens – began the billion-kilometre voyage to Titan aboard the Cassini spacecraft seven years ago, touching down on January 14.

Walter, who has worked for 40 years on the geological evidence of early life on Earth, shared the excitement of astrobiologists worldwide as news of the mission filtered back to Earth.

“We knew that Titan had a very strange atmosphere with a lot of organic compounds like methane and ethane and so on,” he says. “That made it very interesting because it looked like a model of the way the Earth may have been more than three billion years ago and offered insights into how the early organic geochemistry might have occurred here, which eventually led to life.”

However, the initial data from Huygens surprised Walter and the rest of the scientific community.

“Initially we thought that there might be oceans of hydrocarbons, but we’ve since learnt that it’s a solid, frozen surface – at -180C it’s far too cold for liquid water,” he says. “There have only been three or four photos released so far out of the 350 taken by the probe, but you can also see dark patches on the landscape, which is most likely to be something tarry. So I think there is an icy surface, even blocks of carbon dioxide or methane ice, and maybe sticky tarry patches in lower areas.”

While scientists are only just beginning to interpret its data, Walter says the Huygens mission is already considered a spectacular success.

“It’s an enormous achievement for it to have got there and actually had the cameras working for two hours instead of the two minutes that was planned,” he says. “It will take years to analyse the data that comes from this, there’s all sorts of data on the chemistry of the atmosphere and the chemistry of the surface and so on.”

And is there likely to be any photos of little green men?

“I don’t think there’s any chance of life there, I think we’re looking at pre-life chemistry,” says Walter.

For more information on the Australian Centre for Astrobiology at Macquarie University, visit http://aca.mq.edu.au

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