Regular readers of Mysterious Universe are familiar with my “Is There Life on…?” pieces; to name a few examples, I’ve discussed the possibility of life on the planets Venus and Neptune, the moons of Enceladus and Callisto, and even—implausible as it may sound—the Sun. And every time I post one of these pieces, without fail, a reader chimes in and asks: “Is there life on Uranus?”
This makes sense to me; I’m fascinated with Uranus, too. And despite the fact that it's surrounded by a cloud of methane, we actually know quite a bit about it. Yes, scientists have examined Uranus in some detail—to the point where we can render an educated verdict as to whether it can harbor life. And that verdict is “probably not, but maybe."
If you look at the diagram above, you’ll note, already, a few promising characteristics. Methane, a key biosignature, is present in abundance. The mantle includes water which, given the high core temperature, suggests the possibility of a liquid ocean near the core. And with recent discussions centering on silicon-based life forms, the silicate core may even turn out to contribute to habitability in a not-yet-understood way. That’s the good news.
The bad news is that the warm core is also an incredibly dense core. Outside of Drake’s proposed nuclear-molecule based life forms, it’s hard to imagine anything that could survive the kind of pressure that would exist in the core and lower mantle. Add in the fact that the planet actually has the solar system’s coldest atmosphere, and you encounter the same problem we ran into with Jupiter and other gas giants: the outer atmosphere is inhospitably cold and vaporous, while the mantle and core are inhospitably dense. No Earth-based life could survive in either environment, and if any extraterrestrial life has evolved there and adapted to it, we don’t presently know how.
So is there life on the seventh planet? It’s not one of the solar system’s likelier candidates, but we can’t completely rule out the possibility. Surrounded in toxic gas and prone to crush anything that enters its warm depths, Uranus remains a mystery to us all.