So let's talk about taumoeba, astrophage, and predator-prey dynamics.
This was part of the book that bothered me the most, mostly because the rest of the science felt really well-done and at least somewhat thought out (let's not talk about the Sahara project), but this was one area that felt like even a simple skim of the topic should 1) reveal the blatant errors in the book's science and 2) add some cool stuff to talk about in my field that would have been really interesting!
(I'm less bothered by that part of the movie because they didn't say enough to say anything wrong. That's a whole other thing. But at least doesn't involve my field of research :) )
(science below the cut)
(oh hey I can really talk about this stuff. part 1 of 2)
What we know about astrophage is that it's a microorganism that "eats" solar radiation (hence the name) and travels to reproduce around Venus, creating the infamous Petrova line. The dimming of the sun was a slow, gradual process, and there's no Petrova line going anywhere else, so presumably the Sun (and other stars) were "infected" by a handful of dispersing astrophage that slowly built up a population. What that means is that, if all the astrophage around Earth's Sun are destroyed, the Sun may get re-infected later, but there'll be a period with no astrophage.
This is important.
What we know about taumoeba is that it lives in the atmosphere of Adrian and eats astrophage. There are other organisms in Adrian's atmosphere, but they do not eat astrophage, and taumoeba can breed and survive without them for at least long enough for Grace to genetically engineer some nitrogen-resistant strains.
Book!Grace takes this knowledge and decides that, if they introduce taumoeba to the solar system, it will eat all of the astrophage and the problem will be solved. Huzzah! Unfortunately, that's not how this works.
What happens when a predator and a prey species exist in isolation is what's called a Lotka-Volterra curve or equation or model. The predator eats the prey and produces lots of new predators, who eat more prey. Eventually, the prey can't keep up and start to die out. But without enough prey, the predators also start to die out. Eventually, there's not enough predators to hunt down the last of the prey, so the prey population recovers. And on it goes in a pair of lovely wavy curves.
This actually almost never happens on Earth because ecosystems are so complex - when starving, a predator will switch to less preferred prey or migrate (hm), which can keep populations going. But in a space ecosystem with just two species, it's perfect! Grace should be super excited to find the perfect setting for the Lotka-Volterra model to actually work! I am!
So unfortunately, unless they manage to absolutely flood Venus with so many taumoeba they completely wipe out the astrophage in one go before the taumoeba all starve to death, it's not a perfect solution. And even that won't work in the long-term, since the Sun could get reinfected with astrophage and whoops all the taumoeba have starved.
(I suppose they could maintain captive populations on Earth, but given the danger of astrophage escaping to resume eating the Sun, that seems risky.)
What is most likely to happen instead is that Earth will have to adjust to periodic heating and cooling as astrophage populations fluctuate. Ideally it'll eventually reach the equilibrium seen on Tau Ceti, but things are going to be touch and go for a bit even if it does reach equilibrium, and provided that equilibrium isn't reliant on other microbes in Adrian's atmosphere.
Okay so. We've found a species that eats the invasive species we're worried about! We're going to introduce that species and everything's going to be amazing!
...Right.
This unfortunately is the kind of thing that sounds great in theory but is actually a massive risk with the potential to go absolutely horrifically wrong. (Hello, cane toad...)
So let's talk about invasion!
(science below the cut)
(this is part 2! part 1 (predator-prey dynamics) is here!)
When a species is introduced into a new environment, it has to adapt fast. It has to find a new food source, shelter from new predators, manage new diseases, deal with new competitors, etc. A lot of species plopped unceremoniously into a new place will do badly and die quickly.
But some of them, released from their native diseases or predators or surrounded by dumb or defenseless prey will go hog wild.
They'll find a million things to eat where their old habitat had much less. They'll chew through species that haven't survived generations of the "evolutionary arms race" to adapt to their specific hunting/survival strategy. They'll grow bigger and faster than native species, consuming more resources and outcompeting them in their own home. They'll become what's called an invasive species, one introduced to a new environment by human activity that had deleterious effects on said environment. (Note: the exact definition is under debate, that's the version I use). Deliberately introducing a new species, even to deal with a different one, is a pretty wild decision considering all that could go wrong - not only did the cane toad not control populations of the cane beetle in Australia, their poisonous secretions and voracious appetite for anything else that can fit in their mouths is causing major declines in many native species.
So.
The taumoeba could play nice and kindly eat up the astrophage like it's supposed to. Given the solar system doesn't have any other microorganisms out there (that we know of...), it's a bit safer than a lot of Earth systems. But the taumoeba is also capable of evolution, as Grace ably showed, which means there's nothing stopping it from evolving to do something else.
Brainstorming off the top of my head, it could escape Venus's atmosphere into Earth's and decide it likes our microorganisms much better (and become an invasive species). It could evolve whatever process astrophage does (given they're from the same planet and probably evolutionary lines, certainly possible) and start eating the Sun (and become an invasive species). It could form weird astrophage-taumoeba hybrids with the worst traits of both species (...invasive species). Or it could develop a deleterious mutation that spreads rapidly through the genetic bottleneck-ed population and kills it all off. It could do a lot of things, and since it'll be starving after astrophage populations start declining, there'll be a lot of evolutionary pressure for some random mutation to take over (evolutionary pressure here = strong chance of death, means beneficial mutations spread through the population much faster - since everyone without them is dead). And it's got a short generation time, which means beneficial mutations spread through populations fast.
And that's if the whole taumoeba-astrophage system doesn't partially or fully rely on something going on with the rest of the Adrian ecosystem, in which case the whole population could collapse in a few years because of some nutrient deficiency they get from eating some other microbe. Or start displaying some bizarre adaptations normally held in check by other microbes eating them. Or something! The possibilities are a lot!
Honestly, I can overlook a lot of this. It's a fun space movie, and for the sake of Rocky and the power of collaborative science, I can let some things slide. The taumoeba is still Earth's best bet, and I'm sure that they can figure something out, one way or another.
What I can't accept is a scientist like Grace not only not taking the chance to nerd out over predator-prey dynamics but also somehow believing that this is the perfect solution, no notes, nothing could possibly go wrong! Like, he's a science teacher, he knows damn well what an invasive species is!
Give me the science! Give me the nerdiness! Give me samples of Adrian's regular ecosystem for Earth to investigate, and a control sample of original-breed taumoeba as a control! Give me at least a nod towards my field and the challenges we face, like all the space-relevant fields got!
Alas, I have to do everything myself around here... XD
