We haven't found life on Mars yet. That's not too surprising, though disappointing. You can see its surface geology from orbit, plain to view, but any life is likely to be hidden inside rocks, under the soil or beneath the ice.

Pristine deposits of ancient life are likely to be buried meters below the surface, or recently exposed. Any organics left on the surface for long periods of time get destroyed by cosmic radiation and some other process, probably chemical.

The surface of Venus is totally hostile to Earth life, a dim, hot furnace, with temperatures well over 400°C. But conditions are different at the Venus cloud tops. Temperatures are ideal, with plenty of light. The atmosphere is out of equilibrium, with H₂S and SO₂ present together, which life could use as a source of energy. Our orbiters have detected Carbonyl Sulphide - a clear sign of life here on Earth (though it could be created inorganically on Venus); and particles which are non spherical like microbes and the right size for them.

This is an interesting question I was asked recently on the space show. It's inspired by this 5 note theme from the 1970s movie.

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It's the theme tune from Close Encounters of the Third Kind (composed by John Williams), of course, the music the extraterrestrials use to communicate with humans in the movie. Is that just a rather fun movie idea? Or was the director Spielberg on to something, might we be able to communicate with ETs perhaps more readily in music than in other ways?

This special edition of the Space Show may be of special interest if you read my recent science20.com articles about Mars and space colonization. I was asked great questions by David Livingston, and listeners to his live show.

Could Mars One comply with the Outer Space Treaty and planetary protection? What about Elon Musk's Space-X plans to colonize Mars? NASA's plans for a Mars sample return? Missions to the Moon and asteroids? What would it be like to explore Mars from orbit, telerobotically, and never set foot on it in person?