Exploring Alien Worlds on Netflix (Ep3)

Image Credit: Dr. Philip Kramer in the Austrian Alps by Marco Di Marcello


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.

Episode 3

Margaret: Episode 3 starts with a description of how we can understand an exoplanet’s atmosphere and whether it has the right mixture of elements to support life. This is super exciting and the James Webb Telescope, which is scheduled to launch in late 2021, will have this capability. As you can imagine, it’s harder to sample the atmosphere’s around smaller, rocky planets where life might exist than larger gas giants. 

Philip: Detecting oxygen would strongly point towards the presence of life. Since oxygen is so reactive, it would most likely exist in combination with other atoms like carbon, hydrogen, or even oxidized metals. For it to be free of those, it likely indicates an active process like photosynthesis. The planet in this episode is chock-full of oxygen.


Margaret: Eden, our next fictional planet, has 31% oxygen, which is ten percent more than on Earth presently. Eden gets all this oxygen from the epic plant life on its surface–which is fueled by its two stars and an axial tilt that provides a lot of light. Also, a two-star system would make me nervous — it could get unstable fast. All the life we see could be on borrowed time. 

Philip: This planet is definitely more lush and verdant than the others we’ve seen so far. The creators took a lot of time filling this world, though they focus mainly on the relationship between three lifeforms. 


A Grazer sniffing a fruiting fungi. Image credit: Netflix

Philip: The first life we see, aside from the tree and plant life responsible for the photosynthesis, are Grazer. 

Margaret: I did not like their faces. Also, their eyes looked wooden. The design made me wonder what material they were. 

Philip: Yeah. With such narrow pupils, I wonder how any light gets in. Unless it is a compound eye like those of an insect. Now that you mention it, the rest of its features are reminiscent of a moth, from the antennae to the fuzzy coat. I anticipated seeing both common and new sensory organs on Eden. Humans have 21, so it stands to reason that other lifeforms would adapt their own subset of these or more that are specific to their environment.

Margaret: Also, let’s just talk about their (ridiculous) reproductive system. The grazers have to be on the constant lookout for the predators in the trees, which is why they don’t actually have sex. They release worm/caterpillar things that slither along until they find another worm/caterpillar to fuse with. I hated this. Wouldn’t these worm/caterpillars be extremely vulnerable?  

Philip: That was some weird stuff and incredibly complex. Then again, the life cycle of both parasites and moths from which I imagine these were inspired, are also pretty complex. The head of the worm is the textbook image of a tapeworm’s scolex. It’s been over ten years since my last parasitology course, but that’s something you never forget. 

Margaret: Come to think of it, they do look like moths! And let’s talk about how the fused worms turned cocoon lassos itself into the tree branches WHERE THE PREDATORS LIVE. Wouldn’t it be better to just stay as a cocoon on the ground? Can you tell I don’t think this is very believable? Maybe I need to enroll in a parasitology course to get on board. 


A predator consuming a meal with less meat than it would prefer. Image credit: Netflix

Margaret: So these guys look like monkeys but with a secret weapon– a stretchy pair of arms that shoots out of their armpits. I had seen the trailer so I knew this was coming but my boyfriend laughed out loud. 

Philip: I’d be curious to hear how the creators justified this one. An articulated and stretchy arm is counterintuitive. In order to articulate, you have to have some sort of skeleton and joint and those are notoriously not stretchy. This does appear to be the most anthropomorphized species we’ve seen so far. Where does SETI stand on the question of whether aliens will have human-like characteristics?

Margaret: The SETI field is so varied it’s hard to say, but I think there is a universal drive to know what’s out there and how similar it might be to life on Earth. I think the field is constantly challenging itself to think outside of the box and question whether our approach to the search for extraterrestrial life is too human-centric. Put another way, could we miss signs of life on another world because we are only looking for things that look and sound like us?

Philip: Good point. It would be very unlikely for them to have a similar evolutionary history. But there is a strong rationale for why they might look somewhat similar to us. They’ve brought it up in this series before. Those things that are inherently useful evolve independently over and over again, like eyes and venom. I think the symmetry of the face, the arrangement of eyes and ears, nose and mouth, are all there for maximum coverage, height for surveying, and proximity to the brain. The proportions of the human body may prove advantageous for aliens too, with the fulcrum of our elbow and knees less useful for raw power but running and throwing speed. If we ever encounter an intelligent species that needed many of these same advantages, I think they might look humanoid. Though I highly doubt it will be so subtle as a small brow ridge, pointy ears, and green skin.

Margaret: Yes, it would be interesting to see if large brains evolve on other planets. Our brains have given us the ability to organize and take over the planet but they require a lot of resources. In fact, chimpanzees are so much stronger than us even though we’re closely related because they use so much of their energy on muscle mass. We, in turn, use it on our brains. 

Philip: Overall, I think these predators look a bit too human, but they seem to fit in with their environment very well. Especially how they interacted with the other creatures sharing the forest. 

Margaret: Let’s talk about this because if I was critical before, buckle up for what I think about these gross pod things.


Philip: If anything, it’s the fungi the grazers eat which have the more complex life cycle. The spores from the orange fruits that appear late in the season infect the grazers, removes their sense of fear, and makes them more prone to predation. The toxins the spores produce in the grazer then kills the predator, and fungi sprout from its decomposing corpse. 

Margaret: I’m going to try not to blow a fuse. You would think evolution would have selected against this. At some point the grazers would have learned not to eat the orange fruit and the predators would have learned not to eat the prey with the glassy-eyed stare. BUT MAYBE THEIR GENES ARE TOO DUMB.

Philip: It reminds me of a newly discovered parasite on Earth which causes ants to swell and look like berries. Birds eat them, and their droppings are then eaten by ants, completing the cycle. Like these fungi, the fungus Ophiocordyceps unilateralis has some mind altering properties in ants, releasing a specific cocktail of metabolites into the host brain to cause it to seek out an environment more suitable for the fungus. The fungus then infects the mandibular muscles, causing the ant to latch on to a leaf until it dies. Only then will it create a fruiting body and release its spores. These are just two examples of some really complex life cycles right here on Earth. The fungi in this episode is pretty simple by comparison.

Margaret: Also, the fungi kill all the grazers except for the ones in the cocoons. This seemed ridiculous to me. There is no way this ecosystem would last if a key part of it dies out leaving only the vulnerable young. I would have been more okay with this if some of the grazers hibernated. I just don’t understand how this set up could have evolved when it’s so prime to collapse. 

Philip: If they are as dumb and prolific as moths, maybe they don’t need much care. I think it all depends on how developed they are when they emerge from the cocoon. All we get is a shot of a slimy snot ball falling to the ground. Maybe they come out fully developed and ready to eat all the early nontoxic fruit of the fungi. One thing going for this episode, it got me thinking a lot about ecosystems and how every lifeform is dependent on another. As Mufasa would say, everything exists together in a delicate balance.

Margaret: It’s the circle, the circle of LIFEEEEEEEEE!

Exploring Alien Worlds on Netflix (Ep2)

Image Credit: Dr. Philip Kramer in the Austrian Alps by Marco Di Marcello


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. 

Episode 2

Philip: The episode begins with the statement that “all living things need the same things, to feed, reproduce, and evolve.” This isn’t the exact definition of life, though, which is an entity that can grow, reproduce, undergo metabolic processes, and sense and interact with the environment. This simplistic definition has led to some interesting debates. 

Margaret: Yes, it’s a very interesting question. One topical example is whether a  virus is alive. 

Philip: Crystals too can take in energy and materials from their environment and use it to grow and reproduce. Is a crystal alive? Alien life will also likely defy some of these rules. This flexibility is handy when you’re a scifi writer and want to come up with your own alien lifeform. Check out my post on the Science of Exobiology.

Margaret: I got very excited when they talked about extremophiles. Astrobiologists (the people who study the origins and natures of life) are very interested in these microbes because they can teach us a lot about different forms of life, including non-carbon organisms.  

Philip: When they showed the Danakil Depression in Ethiopia, I thought for certain they were showing us some amazing CGI of an alien world at first. I had no idea this existed right here on Earth. A “Gateway to Hell,” or so they named it locally. The organisms here survive in acidic and near-boiling hot springs. Later in the episode, they give another example of bacteria that feed off hydrogen sulfide in dark caves. It makes you really appreciate just how varied Earth’s climates are and the lengths some organisms have gone to in order to survive the most extreme of them.


Margaret: So let’s talk about Janus, which orbits a red dwarf, or an M-type star. These are the smallest, coolest type of star, so a planet has to orbit very close in order to be warm enough to have liquid water. And, as the show points out, being this close to the star means the planet would be tidally-locked. So one side is always light and the other is always dark. The twilight zone in the middle is where most of the action happens.

Philip: It’s strange they don’t show crazy weather patterns on Janus. It can get up to 65C and as low as -50C on the day and night side of the planet. We know from Venus, which also has a slow rotation (its day is longer than its year), that the light and dark side of the planet are pretty similar in temperature due to the winds moving around the planet.

Margaret: True, that would have been interesting to see. Another thing to consider is planets orbiting red dwarf stars may end up without an atmosphere due to the UV radiation and solar flares they experience from being so close to their star. But from the show, it’s clear Janus has an atmosphere. 


A Pentapod. Image credit: Netflix

Philip: These spider-like creatures are the dominant life form on Janus, and depending on which side of the planet they grow up on, have extremely different characteristics. The day-side pentapods  have a dark and shiny exterior to combat the extreme temperatures, while the night-side pentapods are covered in a thick fur.

Margaret:  I thought the different types of pentapods were a little unbelievable at first. They seemed like over-the-top examples of polyphenism.  

Philip: I admit, I thought the same, but they really made me a believer with their description of ant colonies. In order for a single ant species to be adaptable they need members of the colony to specialize, to switch their genes on and off selectively to become either workers, soldiers, and foragers.

Margaret: Okay, fine. I’ll get on board. I suppose. I still think it would be very hard for life to take root on the day-side of the planet. The Pentapods that lived on the dark-side of the planet were more believable to me. 

Philip: They would have more access to water, that’s for sure, but they would also have to expend more energy just to keep from freezing to death. Using their comparison with scorpions, they need far less food to survive the heat.

Margaret: Scorpions! That was a great part of this episode. I had no idea those venomous little suckers  could slow metabolism and go a whole year without eating anything. 

Philip:  As a scientist who studies metabolism, this was particularly interesting to me. Especially the insight into the energy sources of creatures that have no access to sunlight or starlight and the plants that grow beneath it. On Janus, the dark-side pentapods eat grubs around geothermal vents. Insects live off those microorganisms. We see the same principle around the volcanic vents on the bottom of the ocean.

Margaret: What did you think about the way the dark side pentapods ingested the bug’s biolumience?  

Philip: I thought that was a clever adaptation. On Earth, the flamingo gets its characteristic pink color from Astaxanthin in the algae it ingests. But that is a pretty simple molecule. If the bioluminescence is anything like that found in fireflies, which requires a specific enzyme and substrate. I find it hard to believe the protein components would survive a digestive tract designed to break down organic matter. Which brings up the question, what do you make of their overall physiology?

Margaret: The overall look of these animals is very interesting and makes a lot of sense. The ability to move in any direction and see in all directions would be very important if food was scarce. 

Philip: I somewhat disagree with that. Radial symmetry, where the layout of the creature is mirrored on more than one side, is very rare on Earth. Those creatures with radial symmetry are also pretty simple, like the starfish. Replicating so many complicated organs like eyes and appendages on all sides seems like a waste of resources. Scorpions and ants are bilateral, which seems much more efficient. Even the octopus is considered bilateral, and it still puts all of its arms to good use.

Margaret: What did you think about the way they reproduced?

Philip: Their being hermaphroditic means they both have the chance to produce offspring and increase their chances of survival as a species. While it is by no means uncommon on Earth, it is unusual for a creature this size to be hermaphroditic. The fact that it uses the same tooth-lined orifice for reproduction as eating is a bit terrifying. That it launches its offspring like tiny helicopters in the air is also pretty unique, though some species of spiders on Earth are known for something similar. They ride parachutes made of webs to disperse through the air soon after they hatch.


Margaret: I’m glad they discussed the importance of water, but I think it should have come in the first episode. Liquid water is the backbone of astrobiology so it seems like an important point to make early.

Philip: They did say that you need to “follow the water” in order to find life, but we also know that other solvents are being considered like ammonia and methane, and life itself might center around other elements like silicon or boron instead of carbon. 

Margaret: “Follow the water” is an astrobiologist’s life motto! It’s interesting that you bring up methane. It makes me think of Titan, which is a moon of Saturn. It has methane lakes, which makes me wonder about what life could look like there.