The Cassini spacecraft has discovered possible evidence for lakes filled with liquid hydrocarbons around the north pole of Saturn's moon Titan.
If confirmed, Titan would become the only planetary body other than Earth known to host lakes.
A handful of these dark patches have channels leading in and out of them; these channels have a shape that implies they were carved by a liquid.
The US-European probe entered orbit around Saturn on 1 July 2004.
Some of the putative lakes and connecting channels are completely black in the radar images, which means they essentially reflect back no radar signal, and hence must be extremely smooth.
In some cases, rims can be seen around the dark patches, suggesting deposits that might form as liquid evaporates. The lakes are thought to be filled by rainfall, perhaps in seasonal storms.
The abundant methane in Titan's atmosphere is stable as a liquid under the moon's freezing conditions, as is the slightly larger molecule ethane. But liquid water is not.
For this reason, mission scientists are interpreting the dark areas as lakes of liquid methane or ethane.
Cassini team members will image these sites again on upcoming flybys of the moon to determine whether they really are bodies of liquid hydrocarbons on the surface.
The $3.2bn Cassini-Huygens project is a joint venture between the US space agency (Nasa), the European Space Agency (Esa) and the Italian Space Agency (Asi).