Is there life, as David Bowie wondered, on Mars? In this week's Book Club podcast my guest is the astrobiologist Kevin Peter Hand, author of a fascinating new book Alien Oceans: The Search for Life in the Depths of Space. Kevin explains how and where we're currently looking for extraterrestrial life in our own solar system - and why on the basis of sound science he's optimistic that we'll find it. He tells us about the brilliantly ingenious scientific deduction that has established that there exist oceans of liquid water deep under the icy shells of moons of Saturn and Jupiter, why it's quite possible to suppose that aliens might be living in those oceans - and how we can even speculate about what those aliens might look like. And if Kevin's old schoolmate Elon Musk is listening, he has a favour to ask...

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The Book Club is a series of literary interviews and discussions on the latest releases in the world of publishing, from poetry through to physics. Presented by Sam Leith, The Spectator's Literary Editor. Hear past episodes here.