Beneath the icy crust of Saturn's moon Titan may lurk a watery ocean, say Christian Béghin at the University of Orleans in France and his colleagues.
The researchers examined data from the Huygens probe, which landed on Titan's surface (pictured right) in 2005. On its way down, it measured a surprising electric field signal that, on Earth, is caused by lightning. But no lightning has been recorded on Titan, and the signal is instead interpreted as the result of Saturn's magnetic field interacting with Titan's atmosphere and interior. The team says that the signal is most consistent with a crust just tens of kilometres thick covering an ammonia-rich ocean.