RENEE MONTAGNE, host:
Think of a famous explorer and names like Columbus and Magellan pop up - guys with boats. For centuries, ships were crucial to the exploration of our planet. Now a team of researchers has a plan for a boat that would explore another world, a spaceship that would literally sail on an alien sea. NPR's Nell Greenfieldboyce reports.
NELL GREENFIELDBOYCE: NASA is getting ready to issue a call for proposals for what it calls its discovery class mission - relatively low cost exploration projects.
Ms. ELLEN STOFAN (Planetary Geologist): They'll get all kinds of proposals to go all over the solar system - to comets, to asteroids, to the moon, to Venus.
GREENFIELDBOYCE: Have you heard that anyone else is proposing a boat mission to another world?
Ms. STOFAN: Not that we know of.
GREENFIELDBOYCE: Ellen Stofan heads up the team with the boat proposal. I met her at her home in Virginia. She's a planetary geologist who works for a company called Proxemy Research. She says in the past space exploration has been done with spaceships that orbit planets or fly by them, or probes that land on a planet's surface and maybe drive around. So this new idea, floating in an extraterrestrial sea, has got people talking.
Dr. STOFAN: You know, the overwhelming reaction I get from scientists and engineers is, oh, that's really cool. I mean, people are just instantly kind of excited and intrigued to say, could we really go do this?
GREENFIELDBOYCE: The answer is yes, at least on a moon of Saturn, Titan. Besides Earth, Titan is the only place in our solar system known to have bodies of liquid on its surface. A few years ago, a spacecraft orbiting Saturn sent back radar images of the northern polar regions of Titan. The images showed evidence of hundreds of lakes, some of them pretty big.
Dr. STOFAN: Think sort of the Black Sea on Earth, like Ontario, the Great Lakes. Some of them are actually that large.
GREENFIELDBOYCE: That liquid isn't water, though. It's methane. On Earth, methane is a gas, but temperatures on Titan are super-super-cold, minus 290 degrees Fahrenheit. Stofan says when it's that cold, methane is a liquid, sort of like gasoline.
Dr. STOFAN: And it turns out that oddly enough that methane acts just like water acts here on Earth. Methane forms clouds in the atmosphere. It rains down onto the surface and forms rivers, lakes and seas.
GREENFIELDBOYCE: She says imagine you were standing on one of Titan's seashores.
Dr. STOFAN: The liquid that you would see would to you look like water. It would be fairly clear so the landscape wouldn't look all that alien except, of course, from the fact that there is no vegetation at those temperatures. And if you could see through the haze, you might see Saturn hanging off up in the sky, which would be quite a sight to see.
GREENFIELDBOYCE: Okay, so now picture a boat floating on that weird lake. This boat is not going to look like the Mayflower.
Dr. STOFAN: It's certainly not going to look like what most people conceive of a boat looking like. It'll look more like a little capsule that floats.
GREENFIELDBOYCE: Sort of like the bell-shaped capsules that the Apollo astronauts came home in. The vessel will have a mast…
Dr. STOFAN: But that's just to hold a camera. We won't have a sail.
GREENFIELDBOYCE: But the wind would still push this craft around the lake. The probe could drift for months and months. It would have a small, nuclear-powered engine and it could shout its data directly back to Earth. Stofan says there's no danger of a shipwreck, because Titan's lakes have waves, but probably just gentle ones — unless there's a storm. Still, even that doesn't worry her.
Ms. STOFAN: In fact, we'd love for that to happen. Imagine, again, to be able to return an image showing a rainy day on Titan and to see those methane raindrops falling down into the lake, and the wind might kick up a little, but nothing as violent as sort of the tropical storms and hurricanes we get here on Earth.
GREENFIELDBOYCE: She says eventually the ship might just run aground in a muddy beach and get stuck. Stofan says all of this is technically doable. They could launch around 2016 and be sailing on Titan around 2022, if they win the competition to get funding from NASA. Her team is busy working up their proposal. She is supposed to go on vacation next week, but she doubts it will be a totally relaxing. After all, she's going sailing with friends in Thailand.
Ms. STOFAN: Every time we turn the sailboat or anchor, I'm going to be thinking about our probe.
GREENFIELDBOYCE: And what it would be like to be sailing instead on Titan.
Nell Greenfieldboyce, NPR News.