So the first time I heard about the subsurface ocean on Europa (one of Jupiter’s moons), my imagination ran wild. Or should I say it swam wild? I imagined all sorts of wonderful and terrifying sea creatures: krakens with lots of horrible tentacles and teeth; crab-like creatures scuttling around on the ocean floor; and perhaps even extraterrestrial merfolk with a rich and complex civilization of their own.
As I’ve learned more about space and science, though, I’ve scaled back my expectations for what we might find on Europa. Or on Enceladus, or Dione, or Titan, or Ariel, or Pluto… there’s a growing list of planetoids in the outer Solar System where subsurface oceans of liquid water are suspected and/or confirmed to exist.
Any or all of those worlds might support alien life. But not giant sea monsters. When astrobiologists talk about alien life, they’re usually talking about microorganisms. For Europa, rather than civilized merfolk and tentacle-flailing leviathans, we should imagine prokaryotic microbes clustered around hydrothermal vents, feeding on sulfur compounds and other mineral nutrients. If we ever find evidence that these Europan microbes exists, it will come in the form of a weird amino acid residue, or something like that.
That’s the most exciting discovery we can hope for, realistically speaking. Unless…
On Monday, I introduced you to the term “abyssal gigantism,” also known as “deep-sea gigantism.” Abyssal gigantism refers to the tendency of deep-sea organisms to grow larger (sometimes much larger) than their shallow-water cousins. As an example, see the giant squid. Or if you really want to give yourself nightmares, look up the Japanese spider crab.
The more I read about abyssal gigantism, the more my thoughts turn to Europa (and Enceladus, and all the rest). The environment beneath Europa’s icy crust shouldn’t be so different from the deepest parts of Earth’s oceans. So shouldn’t what happens in the deepest parts of Earth’s oceans also happen on Europa?
According to this article from Hakai Magazine, yes. Yes, it should. The same evolutionary pressures that cause abyssal gigantism here on Earth should cause a similar kind of gigantism on Europa. In fact, it would be strange if that didn’t happen. One marine biologist is quoted in that article saying: “You would have to come up with a rationale why [abyssal gigantism on Europa] couldn’t happen, and I can’t do that.”
Before you or I let our imaginations swim wild, I should note that that article from Hakai Magazine was the one and only source I could find on this specific combination of topics: abyssal gigantism and life on Europa. So maybe take all of this with a grain of salt (preferably a grain of Europan sea salt). But… well, I’ll put it to you this way: if someone were to write a story about a NASA submarine being attacked by sea monsters, that story would seem plausible to me.