The image shown above gives convincing evidence; this image was published this week in the journal Nature. Intensity in this colorized image is proportional to how much radar brightness is returned, or more specifically, the logarithm of the radar backscatter cross-section. The colors are not a representation of what the human eye would see on Titan.

The lakes are tinted blue; the radar image strip is foreshortened to simulate an oblique view. The image is centered near 80 degrees north, 35 degrees west and is about 140 kilometers (84 miles) across. The smallest details in this image are about 500 meters (1,640 feet) across.

"The lakes are basically black in the [radar] data, which is how a liquid would behave," Stofan said. Radar data alone wasn't enough, however. A very smooth deposit of fine soil would also appear black on radar, Stofan explained.

The clincher that the patches were liquid lakes came from looking at the surrounding terrain. Some of the patches appeared to be fed by sinuous channels, or "rivers," some more than 62 miles (100 kilometers) long. Others appeared to be contained within rimmed circular depressions, similar to crater lakes or volcanic calderas on Earth.

"The morphological evidence points completely away from it being a smooth deposit of soil or sediment. It's just not consistent," said study team member Ellen Stofan of University College London and Caltech. "Combining these two sets of data, it led us to feel very confident about the interpretation that they're actually liquid."

Science fiction writer Michael Swanwick, writing well after scientists had predicted liquid lakes on Titan, created an enjoyable story about a scientific expedition to this fascinating Saturnian moon. And what would be the best way to obtain samples from a methane lake, now that you've found one? The Mitsubishi robot turbot, of course:

Consuelo carefully cleaned both of her suit’s gloves in the sea, then seized the shrink-wrap’s zip tab and yanked. The plastic parted. Awkwardly, she straddled the fish, lifted it by the two side-handles, and walked it into the dark slush. She set the fish down. "Now I’m turning it on."
The Mitsubishi turbot wriggled, as if alive. With one fluid motion, it surged forward, plunged, and was gone.
Lizzie switched over to the fishcam.
Black liquid flashed past the turbot’s infrared eyes.
(Read more about the Titan-exploring robofish)

Roboticists are working on robofish as fast as they can; see these stories for details:

- Robotic Fish From China
- Robotic Carp Swims Realistically In London
- RoboSalmon Are Descended From SHARCs