Wired.com: So if you had a lineup of Enceladus, Titan and Europa, which are always brought up as good targets for astrobiology, which would you choose?
Porco: Oh, Enceladus wins hands down. Titan has no liquid water on its surface and any liquid water beneath its surface is inaccessible to us, as far as we know. It has hydrocarbon lakes, but we don’t know of any organisms that could live in those, not at the temperatures that we find on Titan. Any reference to possible life in lakes on the surface of Titan is pure speculation.
We do know of subsurface Earth ecologies that could thrive in the subsurface environment on Enceladus. Now that we know there’s salty water there, that shows there’s liquid water in contact with rock. Biotic chemistry could occur that we know exists in volcanic environments miles underneath Earth’s surface, where liquid water percolates through hot rocks.
As far as Europa goes, Europa very likely has an ocean under its surface. In that regard, Europa and Enceladus are on equal par. But on Europa, the ocean is at least several kilometers under the surface and the moon is bathed in an intense radiation field. We can’t go there and just drill several kilometers down because the intense radiation field would fry a properly equipped spacecraft in several months.
So while there could indeed be life within the ocean of Europa, it is presently inaccessible. The beauty of Enceladus is all you have to do is land on the surface, look up and stick your tongue out. It could be snowing microbes at the south pole. We would be foolish not to head back there immediately.
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