On Grace's dwindling food supply, and plants.
Amongst the fans who have both read the book and seen the movie, I think I'm in the minority when I say I have a strong preference for the movie. I'll incorporate book canon into my own personal timeline if it provides context for something or isn't inherently contradictory, but otherwise I try to stay consistent with the narrative beats of the film. I preface with this as I know Grace explicitly states in the book that the Hail Mary does not have a seed bank or plant nursery on board.
That said, in the film, we actually see a small plant nursery during the centrifuge scene. This isn't without precedent; the ISS maintains a small garden on board to learn more about plant growth in microgravity. This has a dual pronged purpose; plants are pretty to look at and gardening provides mental stimulation for astronauts, and being able to grow fresh produce is a simple way to help astronauts meet their dietary needs as we push deeper into space (vitamin supplements can help obviously, but they're nonrenewable and degrade over time).
According to the NASA website, so far, they've had success growing "three types of lettuce, Chinese cabbage, mizuna mustard, red Russian kale, and zinnia flowers." Given that PHM takes place in the relatively near future, it's not a stretch to say that these would likely be the plants one might find on board the Hail Mary as well.
Depending on how green of a thumb Grace is, this has the potential to stave off some of the worst of things like scurvy or VKDB, but would not necessarily help with other conditions such as beriberi (Chinese cabbage is rich in folic acid, or vitamin B9, but beriberi is actually a thiamine deficiency, or vitamin B1). It also would likely not be super helpful at boosting his caloric intake in any meaningful way, given the limited availability of soil.
According to Grace, between his prepackaged rations and the coma slurry, he had enough food to just barely make the four year trip to Erid, meaning his starvation period would likely take place while the Hail Mary is in orbit around Erid. The countdown isn't the trip; it's how fast Eridian scientists can synthesize more nutritionally complete meals once they arrive. This, of course, isn't even factoring in the Taumoeba.
Obviously, Grace in the book does speak retrospectively about battling both scurvy and beriberi, so we know it took long enough for it to become an issue. Depletion of thiamine stores takes around four weeks, and scurvy can take between 40-90 days of sustained low vitamin C levels to develop. I think his exact words were "my first few years on Erid were touch-and-go" so let's say it took about three and a half years to figure out the me-burger
Circling back to the Taumoeba, most microorganisms are going to be primarily comprised of proteins, with some lipids and sugars mixed in. That's all three of your macros, so provided he's actually able to stomach the taste and textural nightmare of the Taumoeba goo, he at least shouldn't get too visibly emaciated... right? Well, maybe, but also maybe not.
The Taumoeba are still, at the end of the day, alien. I think the implication in the book is some sort of panspermia theory, which is why we share things like mitochondria with the astrophage (and the Taumoeba by extension), but that doesn't mean the amino acids they use for their own metabolic functions are a precise one to one with ours. Some might be usable, others might not be. The small amount of lipids and carbs they carry might be in a form we can't easily digest, sort of (but not exactly) like wax esters or dietary fiber.
Clearly he was able to digest enough of the Taumoeba to stay alive, but that doesn't mean it was a great source of food. I mean, textually, it wasn't. However, I do think the plant nursery actually works in our favor here. For one, it's just nice to imagine that Grace still gets to eat a vegetable or two after settling down on Erid. But also the timeline he gives us of multiple years of profound malnutrition is a pretty long time to be that severely malnourished. Both beriberi and scruvy have the potential to be fatal if left completely unmanaged. By being able to supplement the taumoeba with some of the plants from the garden, the three years he mentioned might still be touch-and-go, but maybe just a bit more touch than go.
Would love to hear input from others, particularly any folks who have more experience with things like medicine, biology, or nutrition.
Sidenote: stop having Grace eat live, wriggling cups of Taumoeba. You people are crazy if you think he's not at least cooking that shit.
