Drake’s Equation is a simple formula for estimating the odds of finding intelligent aliens. At first glance, the massive number of exoplanets we’re finding in surveys suggest that there are plenty of opportunities for aliens to develop. However, there are several reasons why the other findings are discouraging.

Some of these worlds have detectable water in the atmosphere. This means they have water. However, some of them have much more water than Earth. That’s both promising and discouraging on several counts.

A water world is ideal for the development of life. It has the universal solvent and a moderated temperature that gives life the best opportunity to develop. The problem is what we’re seeing, and we can draw from Earth’s history to explain why this is a problem.

Early Earth had water. About half of its water came from asteroids. The other half we had from the start. Half as much water still gives you oceans and life – and more land on which smart life could evolve advanced technology. A world with twice as much water, though, is more like the alien world of Thalassa in Arthur C. Clarke’s book “The Songs of Distant Earth”. Life may leave the ocean, but it lacks the land mass to support a diverse, complex ecosystem. At best, you get a few amphibians breeding on the rare islands that exist. You don’t get sentient lizards or apes learning to use fire.

You could have intelligent life under the sea. Smart squid may even stare at the air/water boundary in wonder. But they won’t be able to leave. For example, I don’t think crabs would have developed the ability to scuttle on land if there wasn’t a lot of it to exploit.

Another issue is the relatively low odds of Earth having developed its continents in the first place. Earth version 2 was relatively flat. It may not have had land at all. Then we were hit by a Mars-sized body. The surface debris formed the Moon. The Mars sized body eventually merged with Earth but left us lopsided. That “lopsided” mass was the first mega-continent, and it has reformed several times.  This is why we have nearly a third land mass today. If a solar system lacks the many asteroids ours had early in its history and thus had a very calm geologic history, you don’t get continents on a world that otherwise has them because of said impacts. A calm geologic history also deprives it of the continual influx of nutrients that fed life on Earth. Your smart alien koalas are left on shrinking islands until they learn how to live in the water or go extinct. They’re certainly limited by the near inaccessibility of all the resources that exist on the bottom of the ocean. If you need a nearby target to develop space flight like our Moon, then we may be the only ones with the right conditions to develop space faring technology.

The alternative is just as bad for the development of intelligent aliens. An overactive history means life gets boiled off the surface regularly. Maybe life survives on deep ocean vents, but that life is never going to reach the surface. Even if most impacts are merely disruptive, it only takes one or two to melt the surface the way Venus did several hundred million years ago. Then life starts over if it can at all.

We know nothing of the incidence of volcanism that kept the continents drifting around. A hyperactive planet could nourish life, but we have to wonder if it could develop civilization and advanced technology. A geologically quiet world eventually ends up with miles deep ocean and nothing else. You can have smart squid and maybe alien dolphins, but there’s nowhere for your upright walking intelligences to go.

Where does this leave us? It gives us the possibility of many ocean worlds where life exists, and some may host intelligent undersea life. But we’re the only ones that could leave our world and reach theirs, though whether we’d ever find them under the sea is to be determined.

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Image via Hans (Pixabay)