New radar maps of Titan appear to show that the moon has surface lakes dotted around its northern pole. No solar system object other than Earth has been shown to have standing bodies of liquid on its surface, so the discovery is remarkable.

Titan's lakes would not, of course, be full of water. They would almost certainly be some kind of hydrocarbon - most likely methane or ethane.

The radar maps show dark patches with channels leading in and out of them. Some of the patches are completely black to radar, indicating they are extremely smooth. Others have rims around the edges, suggesting liquid has been evaporating, leaving a deposit behind.

The top image above shows a region around 260 miles by 93 miles. The lower of the two is slightly longer: 295 miles by 93 miles, according to the boffins at NASA's JPL.

Scientists have speculated for some time that liquid methane might exist in Titan's colder polar regions. If these are bodies of liquid, they should change over time - becoming smaller or larger, or even rougher as winds create waves on their surfaces. If they are lakes, this kind of thing should show up in future images of these areas. ®

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• Cassini spots ethane clouds on Titan (18 September 2006)
• Boffins map surface of Titan by accident (25 July 2006)
• Cassini finds land on Titan (20 July 2006)
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