Floating predators. Googly-eyed monkeys. Sky cows. Brain matter in tanks. Sentient robots.
Netflix’s new series Alien Worlds covers them all. Each episode dreams up a fictional planet and the creatures who call it home. When you first see the fantastical critters and colorful plants on each world, you might dismiss the show as pure science fiction, but Alien Worlds is rooted in biology and evolution here on Earth.
What would happen to life on a planet where gravity was twice as strong? How would animals adapt to a planet around a dimmer star? Are we doomed to become a hive mind? Biologist and award-winning science fiction author, Philip Kramer, PhD, and Margaret Reeb, who works at the SETI Institute, have teamed up to break down the series.
Margaret: Okay, Phil. Before we get into the nitty gritty of the show, let’s start with an important question: Do you believe life exists beyond Earth?
Philip: I do believe there is life out there. It’s simply a matter of probability. As the show points out in Episode 4, there are more planets out there than grains of sand on Earth. At least a few of those should have that perfect cocktail of ingredients for life to emerge. The probability of intelligent life is much smaller but that doesn’t keep me from hoping.
Margaret: I’m glad you brought that up. The show doesn’t spend a lot of time discussing the differences between life generally and intelligent life. There are all types of intelligence, but when we say “intelligent life” we’re talking about organisms that can solve complex problems, grasp abstract concepts, and chat with us. I think this type of life is rare but unintelligent life is abundant. (That sounds rude.)
Phil: So we’re in agreement. I did like the way they set up the premise of using biology here on Earth to dream up alien life. There are so many different ecosystems in and out of the water, we can infer so many things about life on other planets.
Margaret: Totally. This is actually the main premise of astrobiology, a cross-disciplinary field of science concerned with the origin and nature of life. Lots of the people who work at the SETI Institute are astrobiologists. They are trying to understand how life came to be in order to find it on other planets. I also want to say that Didier Queloz is a treasure.
Philip: He was the first person we meet in the show, right? He detected the first exoplanet (or planet outside of our solar system).
Margaret: He confirmed an exoplanet for the first time. 51 Pegasi b, or 51 Peg b to friends. We figured there were other worlds but we didn’t know for sure until Didier confirmed it. And 51 Peg b upended our theories about planet formation. Previously, we figured that gas giants planets would orbit far away from their stars, but 1 Peg b is huge–about half the mass of Jupter or 150 times that of the Earth–and orbits VERY close to its star. It’s closer to its host star than Mercury is to our Sun. 51 Peg b was a new class of planet, a Hot Jupiter, and astronomers have found quite a few of them. One idea is that planets migrate–where they orbit changes over the life of the solar system–which would explain how a gas giant ends up close to a star enduring extremely hot temperatures.
Philip: It makes me wonder about the history of Atlas, the fictional planet covered in the series’ first episode. Let’s explore that first, shall we?
Philip: Okay, so this planet is bigger than Earth, so it has a stronger gravitational force and a thick atmosphere.
Margaret: Correct, which is why life on this planet primarily occupies the sky.
Philip: Where do these sky grazers rank for you on the intelligence scale? To me they looked like big flying cows.
Margaret: I spent a lot of the episode trying to decide if they were cute. Jury’s still out. But I don’t think they could hold a conversation with me, unfortunately. I thought the thick atmosphere was a very interesting concept. When they said the sky grazers never landed I gasped. How would they sleep? Then I realized they are sort of like dolphins swimming in the ocean.
Philip: And sleeping isn’t something that all animals do in the same way. The dolphin, like you brought up, can switch half of its brain on and off at a time, so it’s never fully asleep.
Margaret: I did not know that. Another reason dolphins can’t be trusted.
Philip: And while the sky grazers used six wings to fly though the dense atmosphere, the seeds they ate used another method entirely. Buoyancy.
Margaret: Oh, yes. Those were the pods that floated around like dandelion seeds.
Philip: Yes, though not quite like a dandelion seed. A dandelion seed uses air resistance and drag to get around. It can’t go any higher than the breeze will take it. Buoyancy, in contrast, is an upward force generated by the displacement of the surrounding medium as described by Archimedes’ principle. You’re right that the seeds would need some mechanism to lose buoyancy to come back down to the surface from Atlas – either popping or slowly losing the gas that’s giving them buoyancy.
Margaret: Popping sounds too violent. Let’s get back to sky grazers.
Philip: Aside from their potential cuteness, the first thing that stood out to me was their skin. They were very pale. Without some pigment to absorb light in their skin, their cells, no matter what they’re made of, would be susceptible to damage from ionizing radiation. That means there must be something blocking that radiation from reaching them.
Margaret: Yes, and Atlas orbits an F-type star, which is bigger and hotter than our sun, which is a G-type star. (It would also be stable for less time than the sun, which could be a problem.) And Atlas’ star would give off a lot more UV radiation. I’m not sure how that sky grazer would hold up.
Philip: I hadn’t considered the type of star. A thick atmosphere like the one on Venus is known to block most surface radiation. Or like Earth, Atlas might have a strong magnetosphere.
Margaret: And where you have sky cows, you will have predators.
Philip: These are going to haunt my nightmares. When they did the close up shot–
Margaret: Don’t say it! That shot of their toothy beak was unnecessary. I hated it.
Philip: I can’t decide if the beak reminds me more of an octopus’ beak or the bevel of a needle. Having teeth inside was overkill. Those remind me of the lamprey. If you look up a picture of one, you’ll see it has a radial cyclone of teeth it uses to do exactly what they were doing in this show — attach to other fish to feed.
Margaret: I’ll take your word for it. I am intrigued by the way these predators used hydrogen-producing bacteria to move up and down in the atmosphere. Do any animals do this on Earth?
Philip: Bacteria release gaseous byproducts all the time, including hydrogen and methane, but I’m not aware of any symbiotic relationship to inflate an organism. That’s probably because Earth doesn’t have a dense atmosphere. Buoyancy would be a boon to an organism which explains why it would have evolved on Atlas.
Margaret: I liked how they were drawing a comparison between the way these predators hunt and the way falcons hunt on Earth. The falcons hang out up high and dive down on unsuspecting prey.
Philip: I enjoyed that bit. As they say, “nobody ever looks up.” They added another interesting feature to this unique predator, a parachute like membrane that allowed them to produce drag in an attempt to bring the sky grazers to the ground.
Philip: These will also be in my nightmares. This idea of a boneless blob sitting on prey to absorb it is not something I’m aware of occurring on Earth, so it’s unique to this planet.
Margaret: It was heartbreaking when they were picking off the baby sky grazers but the show was making a good point about how tough it can be for young animals to survive.
Philip: They made a good case for why this lifeform will most likely outlive everything else on the planet. “It pays to be a generalist, not a specialist.” This thing didn’t appear to be a picky eater and it’s mode of locomotion was as simple as it gets, literally just rolling around.
Philip: The lack of biodiversity on Atlas really stuck out to me. Earth has a huge amount of biodiversity and we really only see a few things on Atlas. My guess is the creators didn’t have the time to make millions of life forms.
Margaret: I did like how they brought up catastrophic events like asteroid impacts that can change the course of evolution on a planet.
Philip: Yes, and we know that happens because it’s happened here on earth. We’ve had catastrophic events that have wiped out millions of species and made way for new ones. You get a hint of that danger for Atlas from the presence of a ring around the planet. Fragments from whatever those rings once composed could have rained down on the planet.
Margaret: Yeah, that was a nice touch. It reminded me a bit of Saturn, which pulled in an asteroid that orbited the planet for a little bit before getting too close and breaking up due to tidal forces. (Fun fact, the rings around Saturn are relatively new. They didn’t exist when the dinosaurs roamed Earth.)
Philip: We do know that whatever survives such a catastrophic event can quickly evolve to fill all the vacant ecological niches. I read an article recently about how a single species of African Cichlids found its way into a newly formed lake millions of years ago. Over two hundred species of fish have arisen from that, some no more than a couple inches long, and others over two feet. Each filled a particular ecological niche within that lake. Mammals, including ourselves, did the same when the dinosaurs disappeared.
Margaret: Yes, the dinosaurs died because the asteroid impact kicked up so much dust and muck into the atmosphere that killed plants and pumped Carbon Dioxide into the atmosphere. Most dinosaurs were too big to survive this new harsh world, so the tiny mammals who could live on just a little food, water, and oxygen made it through.
Philip: Good point. That was the other thing that surprised me. The lack of water on this planet.
Margaret: Yes! Water is extremely important in the study of astrobiology, and the show really dives into the importance of liquid water in the next episode.