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Thursday, September 17, 2009

Sailing a Ship on an Alien Sea. Your Astronomy Moment of the Day.

We could have a capsule sailing an extraterrestrial sea as soon as 2022, if a team of researchers can convince NASA to try sailing a boat on an alien world.

Ellen Stofan, a planetary geologist at Proxemy Research in Maryland and an honorary professor at University College London is suggesting NASA do just. She is leading an effort to design and propose a low-cost mission to Titan, one of Saturn's moons.

Sailing — But Not In Water

Titan is the only place in our solar system other than Earth known to have lakes on its surface, Stofan says.

The liquid isn't water, of course. Temperatures on icy Titan reach minus 290 degrees Fahrenheit. The lakes are actually liquid methane and ethane.

Here on Earth, methane is an odorless gas. But on Titan, methane acts just like water acts on Earth. Methane forms clouds in the atmosphere. It rains down on to the surface and forms rivers, lakes and seas.

This radar image taken by the Cassini Space Probe in July 2006 of Titan, one of Saturn's moons, provides evidence that it is covered by large bodies of liquid.

Titan's Great Lakes

A few years ago, the Cassini spacecraft sent back radar images of the north pole of Titan, and those pictures showed evidence of hundreds of lakes. Some of them are large — the size of North America's Great Lakes.

One of the large lakes — either Ligeia Mare or one called Kraken Mare — would be the target for a probe that would splash down and float around, according to the plan that Stofan is working on with some other Titan experts.

And that would be something new. In the past, space exploration has been done with spaceships that orbit planets or fly by them, or with probes that land on a planet's surface and maybe drive around, like the Mars rovers.

Floating Space Capsule

The "boat" or "lake lander" that Stofan is designing with her colleagues would not look anything like the ships used to explore Earth back in the days of Christopher Columbus or Ferdinand Magellan.

"It's certainly not going to look like what most people conceive of a boat looking like," says Stofan. "It'll look more like a little capsule that floats." She says it will drop straight into the sea. It will have a mast, "but that's just to hold a camera. We don't have a sail," she says.

Titan's wind will push this capsule around the lake. The probe could drift for months. It would have a small, nuclear-powered engine. And it could shout its data directly back to Earth.

There's no danger of a shipwreck, according to Stofan. Titan's lakes have waves, but probably just gentle ones — unless there's a storm. Still, even that doesn't worry her. "In fact, we'd love for that to happen, to be able to return an image showing a rainy day on Titan and to see those methane raindrops falling down into the lake," she says. "The wind might kick up a little, but nothing as violent as sort of the tropical storms and hurricanes we get here on Earth."

Eventually, she says, the ship might just run aground in a muddy beach and get stuck.

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