Titan: It's a Small World After All

A comparison of one of Titan's 'seas'(left)
and Lake Superior. Credit: NASA/Cassini.Saturn's largest moon, Titan, has always held my imagination in a tight grip.

Even back in my childhood (we're talking the 60's, before any interplanetary probe had even crossed the Asteroid Belt just beyond Mars), when we knew little more about Titan than its large size and the possibility that it might have clouds, I was spellbound. After all, the fewer hard facts you have, the more power your imagination has, right?

I read science fiction stories that presented Titan as a world with atmosphere, weather, clouds, and even seas of liquid (albeit seas of water and a breathable atmosphere...).

In retrospect, how prophetic some of those stories were. In the past two years, NASA's Cassini spacecraft, now wrapping up its third year in orbit around Saturn, has revealed features on Titan that, in my mind, place it into the class of world. (Not planet, of course; even before the word planet was defined scientifically, Titan wasn’t one simply because it orbits an actual planet, and not the Sun.)

Early in 2005, the European Space Agency's Huygens probe, which was deposited on Titan by mothership Cassini, sent back aerial pictures of features on Titan’s surface that looked for all the world like meandering coastlines. These "coastlines" divided areas of land etched with what looked like river drainage networks and dark, flat expanses that gave the impression of being some sort of liquid surface. Huygens’ measurements also suggested that the ground on which it touched down may have been more like damp soil rather than dry desert dust and rock such as we've found on Venus and Mars.

Huygens ran out of battery power hours after landing-- but Cassini flew on, circling Saturn in long, wild orbits that have carried back by Titan on more than one occasion... for some very exciting results.

In 2006, Cassini’s instruments--in particular its radar--revealed yet more liquid-body-like features: "lakes," as they were called. The series of lakes, located in Titan’s high latitudes, ranged in size from about half a mile wide to 62 miles across. The lakes were believed to consist of liquid methane and ethane—compounds that exist in their gaseous state on Earth, but which would be liquid under the extremely cold temperatures of Titan. (Water on Titan would be solid ice.)

Most recently, in March this year, Cassini discovered not more lakes on Titan, but seas-- seas-- near Titan's North Pole, one of which is larger than any of the Great Lakes of North America.

I have learned that I was wrong. I always assumed that the imagination has its greatest power to visualize fantastic places and things when it has the least factual information to go on—just as a blank canvas gives an artist the most freedom to create an image. But I’m finding that the more I hear about the scientific discoveries on Titan-- its hydrocarbon clouds, its probable rain and wind systems, its possibly muddy surface, its rivers, its lakes, and, yes, its seas, my imagination of this small world is positively stoked...

Benjamin Burress is a staff astronomer at The Chabot Space & Science Center in Oakland, CA.