Astronomers at Cornell University, at Ithaca in the US state of New York, have used radar data to determine that the biggest sea on Titan, the largest moon of Saturn, is, near its centre, at least 300 m deep. The sea is named Kraken Mare, and it is estimated to have a surface area of some 400 000 km2, which would make it bigger than Earth’s Caspian Sea. Titan is the second largest moon in the Solar System and is larger than the planet Mercury (the largest moon is Ganymede, which orbits …