The universe is really, really big, and there’s a very good chance that it’s teeming with civilizations advanced enough to contact us, if not visit us directly. So why hasn’t it happened? That’s the question at the center of the famous Fermi Paradox, and it’s given life to a bunch of intriguing possibilities: maybe there’s something stopping all civilizations from becoming interstellar. Maybe they’ve uploaded their collective consciousness to a huge computer. Maybe they’re all asleep. Well, one scientist is tossing a new theory into the ring. Maybe they all live on frozen ocean worlds, and they can’t get past the icy crust.
Under The Sea
Planetary scientist Alan Stern of the Southwest Research Institute in Boulder, Colorado looks at it this way: ocean worlds are incredibly common in our solar system, which means they’re probably just as common throughout the universe. While it might seem outlandish to think that liquid water could exist beyond the reaches of our sun’s warmth, it does: Jupiter’s moons Europa, Ganymede, and Callisto all have liquid water oceans, as does Saturn’s moon Enceladus. Even the dwarf planets Pluto and Ceres show signs of water beneath their outer crusts.
But unlike the water on Earth, the water on these nearby worlds exists beneath a thick layer of ice or rock. Still, that doesn’t mean life can’t survive there — not even close. Just as life on Earth sustains itself in the deep sea thanks to the warmth and chemicals pumping out of hydrothermal vents, extraterrestrial life could be thriving in the vent systems produced via the geological activity of their ocean worlds. And if you’re living on chemical energy from your own planet instead of solar energy from a star, your planet could potentially be located anywhere. Habitable zone, schmabitable zone.
Lost Souls Swimming In A Fishbowl
So who’s to say the life on some of these worlds hasn’t advanced to our level — or beyond? If they did, their experience of the cosmos would be very different from our own. Instead of looking up into the night sky to see billions of stars, they would only see the icy crust above them. While ice would be an excellent shield from cosmic radiation and meteor impacts, it would also block many radio signals, as NASA researchers discovered in 2013 when attempting to measure the Arctic ice sheets using radar.
For these civilizations, boring a hole to their planet’s surface would probably be the first step to any space program, and that’s no small feat. Europa’s crust, for example, is estimated to be at least 10 miles (15 kilometers) thick — by comparison, the record for deepest hole drilled into the Earth is still only 7.5 miles (12 kilometers). That’s a big hurdle to jump just to send a message out into the void.
There could very well be super-advanced civilizations swimming beneath the icy crusts of many ocean worlds, but they’d be so self-contained that they may never think to look for life beyond their planet. It’s like a goldfish living its entire life alone in a fishbowl, never knowing it could commune with an ocean full of other fish if it only had the means to get there. But in this case, maybe we’re the only fish in the ocean. Everyone else is just living in their own fishbowls.