A river, way out there

Phil Plait, the creator of Bad Astronomy, is an astronomer, lecturer, and author. After ten years working on Hubble Space Telescope data and six more working on astronomy education, he struck out on his own as a writer. His two books are Bad Astronomy: Misconceptions and Misuses Revealed, from Astrology to the Moon Landing "Hoax" and Death from the Skies! These Are the Ways the Universe Will End. He has also written dozens of magazine articles and twelve bazillion blog articles. He is a skeptic and fights the abuse of science, but his true love is praising the wonders of real science. Plait has a Slate article about more weirdness in the universe:

The amazing astronomy news keeps on coming! This one is very cool: what appears to be a four hundred kilometer long river of liquid has been found near the north pole of Saturn’s moon Titan. You can see the river in the picture at left, which was taken in September of 2012 by the Cassini spacecraft orbiting Saturn. The river appears dark against the lighter background of Titan’s surface. While this isn't the first river network seen on Titan, it's the longest, and this is the highest-resolution image ever made of one.
Cassini has flown by Titan several times, making detailed observations of the giant moon. Titan is huge, bigger than the planet Mercury, and has a dense atmosphere made of nitrogen. The top of the atmosphere has a thick layer of haze, making it impossible to see the surface with visible light. Infrared can penetrate the murk, as can radar. Cassini has the capability to use both, and has been making maps of the surface for years. It’s found huge sand dunes, structures that look like volcanoes and a series of smooth, dark regions at both poles that look very much like lakes.
Then, in 2009, proof of liquid lakes came when a reflected glint of sunlight was seen off one of those dark regions. This sort of reflection can only come off something highly reflective such as a liquid, confirming Titan has huge lakes filled with some kind of liquid.
But what liquid? On Titan it’s so cold that water is literally frozen as solid as rock. But other substances have much lower freezing points, such as ethane and methane (which are natural gases here on our toasty Earth). Hydrocarbons are plentiful on Titan, so ethane and methane are abundant and almost certainly what’s in those lakes.
In fact, on Titan those liquids act like water does here on Earth, evaporating into Titan’s atmosphere, blowing around, raining down, and starting the cycle over again. It’s been suspected rivers might exist, but this is the first one seen. Note how it looks dark and smooth, which is a distinguishing characteristic of the lakes seen as well.
The length of this river, and the fact that it’s mostly straight, imply the liquid is flowing along a crack in the surface of Titan, perhaps a fault line in the surrounding bedrock. You can see tributaries feeding into it as well, with it finally flowing into a lake at the top of the picture.
That’s just plain amazing. And it sets fire to the imagination: life on Earth is based on carbon molecules and needs liquid water to survive. Ethane and methane are carbon-based, and liquid to boot. Scientists have speculated for years that Titan might be a good place to look for life— though at a temperature of -290 degrees Fahrenheit it would be a lot different from us and would probably operate at a much slower pace. Still, it’s fascinating to try to imagine what sort of life might possibly arise on such a distant, chilly, alien world.
But, life or not, this is still a fantastic scientific find. The more we learn about the myriad of planets and moons in our solar system, the more amazed I am at their diversity, complexity, and ability to surprise us. Titan may be alien, but when I see a picture like this— a Nile river in miniature— it’s hard not to think about how much we have in common with all these worlds.

Rico says that the movie 2010 had life on Europa, not Titan, but the notion's the same...