There’s been a lot of questions about how deep the methane seas of Titan really are — are they deep, permanent features, or shallow seas that come and go with the seasons? Until Cassini, no one could even find the seas, and it took many passes by Cassini over the slow change of seasons to get an answer (Titan’s seasons match Saturn’s, which means it takes 29 years to complete the cycle). During the last pass, Cassini had the opportunity to turn its radar beam onto Kraken Mare, the largest of Titan’s seas, which has a surface area greater than Earth’s Caspian Sea. And they got some good data — they can definitely rule out a shallow sea, at least in this case. In the region measured, the depth ranged from 66 to 115 feet, which is respectable. For comparison, Lake Erie, the shallowest of the Great Lakes, has an average depth of just 62 feet — though its greatest depth is 210 feet. The strip of methane sea that got measured did not go through its widest swath, so it seems reasonable to expect there are greater depths elsewhere.
So Kraken Mare is a proper sea, I think we can say. Now we’ve just got to drum up the funding to get Titan Mare Explorer out there. 😉