We're in a military space cruiser, designed for in-system patrolling. We're selected to test out a prototype FTL drive. The initial tests are supposed to be short-ranged in-system hops.

A disaster happens and we're forced to make an unprepared long-distance jump to a distant system. Thankfully, we know that the system has a world that should be habitable, and when we arrive in the system our scans show this is true.

However, further Bad Things happen, and we have to abandon the ship. This isn't rushed, but we can't take, say, the primary computer core or the machine shop. We can bring along some solar panels for recharging of the portable devices, but that's about it.

How do we go about determining if something is not only edible/non-poisonous, but that we are getting the nutrition we need?

  • $\begingroup$ just spit on the thing and wait 1-2 days. If the thing is edible and has nutrient value, probably there will be some bacterial activity. Same as with some types of beer recipes, human saliva contains ferments which split particular hydrocarbon polymers. Anyway, If nothing will happen with the thing at all - that will be a bad sign. $\endgroup$ – MolbOrg Mar 15 '17 at 23:28

What to do if you find yourself stuck with no hope of rescue: Consider yourself lucky that life has been good to you so far. Alternatively, if life hasn't been good to you so far—which, given your present circumstances, seems more likely—consider yourself lucky that it won't be troubling you much longer. -Hitchiker's Guide to the Galaxy

Sometimes the answer to this sort of thing is "everybody dies." In fact, that's usually how it goes with major mishaps. The real question is how well you prepared for the unknown unknowns. Rumsfeld got laughed at for that phrase, "the unknown unknowns," but it really is the key. How do you deal with the things you don't know about until you know about them.

Hopefully your ship has a large amount of rations. You may need months of rations to pull this off. Living on a foreign environment is extremely tough. You're going to need to be almost completely reliant on rations in the beginning, and hopefully be able to ween yourself off of them as time progresses.

In survival situations there's an order of operations that is universally recommended: Air, shelter, water, food. It's known as the rule of 3's based on how long you can last without them: the human body can survive 3 minutes without air, 3 hours without shelter (in a harsh environment), 3 days without water, and 3 weeks without food. You say it's a habitable planet, so let's assume that air is easy, and you say you have an abandoned ship to work with, so you probably have shelter. So let's get to work on the others.

The first step would be water. Hopefully you have a reasonable supply of water on board, but it might damaged. Setting up survival tools like solar stills may be essential. They have the advantage of also purifying the water before you drink it, which has benefits in an alien landscape. However, you weren't too interested in water, you were interested in food. That puts us in the weeks timeframe, plus whatever rations you have.

Now the good news is that it is highly unlikely that anything in this ecosystem is going to be gratuitously toxic. Most toxins are co-evolved with the particular life they grow up around. For example, lactotoxin, the toxin in Black Widow venom, specifically targets neurons, binding to protein structures that identify them. You are an alien in this environment, so are likely to not be targeted by their targeted toxins. You're more likely going to have to deal with very simplistic chemical attacks (acid/base, redox) and accidental toxicities (like heavy metals).

The good news is that our bodies are designed to deal with this sort of thing. In survival they teach you an approach to minimize the risk of poisoning yourself with an unknown food source. The first step is not to eat unknown things, though survival situations rarely let you be so picky. If you do need to eat something unknown, you do it in stages. First you rub a bit of it on your skin. Our skin is an amazing rejecter of a lot of bad things, and it tends to respond to attacks. You look for redness. If you swell up here, be glad you didn't eat the food first. After an hour/few hours, you can try rubbing it on your lips. Lips are a lot thinner and more sensitive. One of their evolutionary jobs is to detect the difference between food and not food, so they're good at it. If you have no reaction, you use your tongue. Then you finally take a nibble. Each time, you give your body (the world's most advanced chemistry set) time to analyze the compounds.

That should pick up all basic acute toxicity issues, and because you're the alien, you're unlikely to have to deal with any subtle toxicities. So that answers the first half: how to determine it's not poisonous.

The latter half is trickier. There's a really good chance that the ecosystem you landed on doesn't support the amino acids we need. We're going to have to be creative.

The first step for food is sugars. Your body needs something to burn. That's the first layer of nutrition. It can burn a lot of things, like fatty acids, so if you find those, great. However, you're most likely to find sugars because they're simple. They're also pretty easy to find because, evolutionarily, we needed to find them. Our tongue is remarkably good at determining what has sugar content in it.

The next layer is minerals. These may be harder to get from the edible foods around you because they will have arrived at a different balance of minerals than we need. We actually don't need much (most primitive cultures ate several hundred times the US RDA of many minerals that we have trouble finding in our diet today!), but if we did have trouble, I'd go straight to the source: dirt. There are famous clay licks for parrots who live in environments which are short on minerals. Clays are an amazingly good source of them. You might find that mud pie is actually on the menu.

The hardest part would be the amino acids. Nine of them are simply required by the human body: phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine. Five more are considered important because we only create them within our body in times of great stress: arginine, cysteine, glycine, glutamine, proline, and tyrosine. Finding these could be very difficult. It's highly unlikely that the life on this other planet has these amino acids. You're going to have to be creative.

Or you need to enlist creativity. Consider yeast. Yeast is known to produce many of the essential amino acids we need. And, unlike you're crew, you're comfortable if a few billion of them die trying to evolve to adapt to the environment you're in. Yeast is your single-celled weapon of choice in this foreign environment. It will naturally breed within the human-controlled areas, but may also be in the best position possible to evolve into something that can function in the alien ecosystem. Careful cultivation of yeasts to survive the harsh climate may be your best bet for generating the very exacting amino acids you need to survive.

Beyond that, it's all really guesswork. I'd say your success is based 0.00001% on how prepared your crew is to survive, and 99.99999% based on the particular chemistries of the planet you landed on. To make your story more believable, I'd recommend choosing a few atypical chemistries to apply to your planet which your crew can then find clever ways to take advantage of to make it feel more realistic. You're not trying to make the planet into your home, you're trying to survive on the planet you've been given.

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  • $\begingroup$ Rations are likely to be available in quantities: Slower-Than-Light travel inside a system takes a lot of time. And yeast is something I hadn't thought about - And something that would likely be available. It's used in a lot of baking, so it's not terribly far fetched that it would be on the ship in some quantity. $\endgroup$ – Andon Mar 15 '17 at 22:21
  • $\begingroup$ A real problem for these castaways is the problem the Martians encountered on earth in War of the Worlds. Our bodies are succulent wads of reduced carbon. Our immune systems might not be ready for the things that break down such succulent wads in an alien land with chemistry like ours. $\endgroup$ – Willk Mar 16 '17 at 0:30
  • $\begingroup$ Alternately, those alien things might not be ready for us and have little/no effect, like @Cort Ammon mentioned about toxins. $\endgroup$ – Andon Mar 16 '17 at 4:04

This sort of thing always reminds me of The Way to Eden episode on Star Trek. When the hippies get there it is beautiful but every single thing is totally poisonous. Walking barefoot even burns the girls' feet.


Headin' out to Eden.... yeaaa brother.. And Spock plays the harp!

  1. Touch thing. If it hurts your skin don't eat it raw. But some things that hurt skin are fine if you cook them - for example stinging nettles. The skin piece is its defense and once you undo it there is no other defense. It is not poisonous. Not so poison ivy.
  2. See if mammal eats thing. That works better if there are mammals.
  3. If a fruit, see if fruit flies land on rotten ones. Fruit flies like fruits that are ok for humans, not so much the ones that aren't. That works better if there are fruit flies. Maybe you brought some?
  4. Eat a little bit of thing.
  5. If you don't get sick, eat some more.
  6. If you get diarrhea, try boiling the thing and changing the water a few times, then eat again.

If there is an animal and it is very quick, or has sharp spikes, or is armored, those are probably its defenses from predators. Probably it is not poisonous also. Try eating those according to above algorithm.

If you are losing a lot of weight and you are hungry, you are not getting enough calories. After that it gets harder. If you can recognize signs of scurvy or pellagra or other deficiencies you can conclude you are deficient in the nutrient responsible for preventing the one you have. Other things can mimic those symptoms (rash, diarrhea, sore mouth)- like weird alien diseases, or being poisoned. Even if you knew for certain that your diet was too low in, say, B6, there would be no way to figure out what in your environment had B6 in it. Maybe nothing.

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You mean the planet is inhabited? We don't know why our amino acids are all L-stereoisomers. If it turns out that that is just random, then there's a 50:50 chance that the amino acids on the planet will be D-isomers.

It might be possible to convert them to a racemic mix with long cooking. That's assuming that the life is protein/carbohydrate based, like we are. If that isn't true, after the food runs out, you start eating each other.

More optimistically, it seems to me the best chance a crew would have, absent the analytical equipment, would be to use their own excrement to culture native bioorganics to grow more Earth organisms. Shit has both bacteria as well as algae and fungi (and of course, viruses).

You'd have to get creative and try a bunch of different ways to grow slime, hoping that they'll work. You have three problems:

  1. Getting the calories you need. Well, if native flora and fauna kill the germs in crap, they'll kill you too, so kiss your ass goodbye (assuming cooking doesn't fix that problem). Once you've got Earth stuff growing, you'll probably be able to get the calories you need.
  2. Getting the nutrients you need. Well, you can look up what is needed for essential nutrients. It's probably true that the oils (given similar enough biology) will be available, but you might need some chemistry books. For proteins see above.

Finally the difficult issue would be the removal of toxins and carcinogens in the food. As an added problem, if your biology is similar enough to that of the planet for you to eat it, then it can eat you.

Your immune systems are likely to be ineffective, and their local germs will probably kill you all. This is all assuming you haven't brought along a couple hundred pounds of intact potatoes, or a few sacks of rice and corn seed. Of course, Earth plants may be just as susceptible to the planet's bugs and germs as you are...

Really, the only way you can determine whether you're getting the nutrition you need is to monitor your weight and health (absent some pretty sophisticated chemical analysis instruments) as you incorporate some of the slime or local food into your diet.

Trial and error, in other words. As an aside, I find it amusing that you think batteries or solar panels are going to save you. (You didn't mention, does the planet have enough oxygen and not too much of anything lethal? Is the temperature < 50°C but >0°C? Is there land? Liquid water?)

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  • $\begingroup$ You should ask the OP in comments for clarification if you think something need to be defined and is currently missing. By adding these detais he could otherwise possibly invalidate your answer. $\endgroup$ – Secespitus Mar 15 '17 at 20:43

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