Top of the Loop, Bottom of the Loop

Every plan for living off Earth has a page for oxygen, a page for water, and a page for food. We have not yet seen one with a page for worms and a page for bees. From what we have found in our research, those two pages may decide whether the food page means anything at all.

Here is the chain, as best we can lay it out. Crops need soil. Soil is not dirt; it is dirt that has been worked over by living things until plants can use it, and on Earth the animal doing most of that work is the earthworm. Worms need something to eat, and what they eat is dead plant material and animal waste. The animals need plants to eat before they can produce waste. And the plants need to be pollinated before there is a next generation of plants at all. On Earth, a great deal of that pollinating is done by bees.

So the loop has an animal at the bottom, building the ground, and an animal at the top, making the seed. Take either one out and the loop does not close. It just leaks until it stops.

Bottom of the loop

We started this line of thinking with a simple question: what happens to worms when the ground freezes? The answer, from what we have read, is that most of the common composting worms die, but they leave behind cocoons — small, rice-grain-sized capsules you can see with the naked eye — and the cocoons survive frozen soil and hatch in spring. A red wiggler lays two or three a week, each holding two to six young, and a hatchling is a breeding adult in about two months.¹

That is a useful trait for a habitat. A colony that can lose every adult to a cold snap or a power failure and rebuild from a handful of seeds is a colony you can keep in a jar on a shelf as a backup.

The rest of what worms need is less forgiving. They breathe through their skin, which has to stay wet, so they cannot live in dry dirt and they drown in flooded dirt. They need grit for the gizzard, but they pick that up themselves as they eat. And they need feed — constantly.

Here is where it gets interesting for anyone thinking about the Moon or Mars. A team led by Donato Romano at the Scuola Superiore Sant’Anna in Italy put red wigglers into lunar regolith simulant mixed with dried cow manure at different ratios and watched them for two months. Mortality went up as the regolith fraction climbed, but most of the population survived, they kept producing cocoons, and they tunneled more in the mixes with more rock in them — the authors suspect because they were searching harder for food.² Nobody shipped soil to the Moon in that experiment. The worms started making it out of ground-up rock and manure.

Notice what had to be shipped: the manure. The worms did not build soil out of regolith alone. They built it out of regolith plus something already dead and organic. That is the bootstrap problem in one sentence. On a sterile world there is nothing dead to eat, so the first load of feed has to come with you, and it has to last until the first crop is producing waste of its own.

What worms will and will not eat

From what we have found, worms are not particular about species but they are very particular about texture. They want soft, damp, already-rotting material. Tough, waxy, high-tannin leaves — oak, conifer needles — get left alone. That is not a detail. It means the choice of crops in a habitat is partly a choice about what your worms can digest. Leafy crops break down fast; grain straw and corn stalks are the hard cases.

Worms also do not eat their own castings. Once a bed is fully worked over, the energy is gone and the colony moves on or dwindles. Every pass through a body costs something, so the system leaks without new input. That is another way of saying the same thing: the worm bed is not a machine you install. It is livestock. You feed it, water it, keep it warm, and it works for you. Neglect it and the whole loop stops.

The other edge of the shovel

Before we get too fond of the earthworm, our research turned up something we did not expect. Across most of the Midwest and Eastern United States, earthworms were rare before European settlement — they had not recolonized after the last ice age — and the worms there now came from Europe and Asia.³ In the northern hardwood forests those imported worms have been stressing sugar maples, thinning the leaf litter that native plants and insects depend on, and setting off food-web changes that help invasive plants spread.⁴

The same traits that make a worm wonderful in a garden make it dangerous in a forest that evolved without one. So the question is not just “how do we ship a ton of worms to Mars.” It is “which worms, in what numbers, alongside what else,” because we will be building an ecology, and an ecology with the wrong animal in it can tip in a direction nobody planned.

Top of the loop

There is a line people like to attribute to Albert Einstein: if the bees disappear, mankind follows within a few years. We have looked, and we have not been able to find any record that Einstein said it or wrote it; it seems to surface in beekeeping circles decades after his death. We are not going to hang the argument on a quote we cannot source.

That said, it stands to reason that pollinators are necessary, and our research suggests the honest version of the claim is narrower and still serious. Wheat, corn, rice, and the other grains are wind-pollinated; they would carry on without a single bee. What would go is most of the fruit, the nuts, many of the vegetables, and the seed for the next planting of anything that needs an insect to move pollen. A habitat that lost its pollinators would not starve outright. It would eat grain and lose everything else, and it would lose the ability to make its own seed for what it lost.

Bees in a sealed habitat raise problems we have not seen answered anywhere:

• A hive needs forage all year, not just when the main crop is in bloom. Between crops it starves unless something is always flowering or someone is feeding it sugar.
• A healthy hive swarms — half the colony leaves to found a new one. In a sealed cylinder, where does it go?
• Bees navigate by the sun’s angle and by gravity. In a rotating habitat the “down” direction is centrifugal, and a flying bee crossing the spin would feel Coriolis forces that no bee on Earth has ever felt. Whether a bee can learn to fly straight under those conditions is, as far as we can find, an open question. It looks to us like a very good experiment, and one that could be run on a centrifuge here on the ground. If anyone reading this knows of such work, or wants to do it, we want to hear from you.

The last time we tried this

None of this is theory. It has been tested once, at scale, and the results are on the record.

Biosphere 2, the three-acre sealed glass structure in Arizona, was built to find out whether eight people could live for two years inside a closed ecology. They went in with a rainforest, an ocean, a savanna, a farm, and roughly 3,800 species. By the end of the first mission, nineteen of the twenty-five vertebrate species brought inside had died out, and virtually every pollinating insect was gone — the honeybees included.⁵ Plants that needed insects could no longer set seed on their own.

What thrived was the opposite of what was planned. Cockroaches boomed. And one ant, the longhorn crazy ant, Paratrechina longicornis, got inside without anyone intending it, competitively excluded every other ant species in the building, and ended up living almost entirely on honeydew from the sap-sucking insects it tended on the plants.⁶ It was farming aphids. It never needed the crops at all.

Nobody has published a single confirmed cause for the death of the bees, but the explanation we find most convincing starts with the glass. Ordinary greenhouse glass blocks most ultraviolet light, and bees see and navigate in ultraviolet — flower markings, polarized sky light, cues invisible to us. A bee that cannot see the sky the way it evolved to see it cannot forage. Add a bloom that was thinner than expected, no wind, and colonies too small to buffer their losses, and the hives starved.

The wind matters more than it sounds. Biosphere 2 had large air handlers running constantly, but ducted circulation is not weather. The trees inside grew fast and weak and some of them fell, because a tree that never feels a load never builds wood to resist one. That is a lesson we intend to come back to in its own article, because it applies to everything in a habitat, not just the trees.

Where this leaves us

We are not going to pretend we know the recipe. Nobody does yet, and that is the point of asking. But from what we have found so far, a habitat that intends to feed itself will have to treat two animals as core life support equipment and budget for them the way it budgets for air:

At the bottom, worms — shipped wet, shipped with their first meal, chosen for the crops they will be asked to digest, and kept as a colony with a cocoon reserve in case the bed crashes.

At the top, bees — with year-round forage, a plan for swarms, light that includes the ultraviolet they navigate by, real moving air, and an answer to the question of whether they can fly straight in a spinning room.

And underneath both, the humility to remember that the last team to try this had a rainforest and an ocean and a farm, and lost the bees anyway, to a stowaway ant that farmed aphids while everything around it died.

Ideas in Star Bound are published open — take them, build them better. Our open proposal.

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A note on where this comes from. I am not a metallurgist, a spacecraft engineer, or a degreed engineer of any kind. But I am a practical one, with more than forty years in heavy industrial construction: welding, millwright work, hydraulics, mining, and thirty-three years of electrical construction and commissioning on the North Slope of Alaska, in a place that punishes anything built wrong. Much of that time I have worked as a field engineer, which means I am the one standing in front of the equipment when the drawing turns out to be wrong, and the fix has to be made on the spot, with what is on hand, and has to work the first time. Anyone who has done that long enough learns that a lot of engineering gets corrected in the field by people with more experience than the people who drew it. That is the eye I bring to these subjects: not what should work on paper, but what actually gets built, and what breaks. The facts I take from other people are footnoted so you can check them and read further. The ideas built on top of those facts are my own, and I would rather see them knocked down by somebody who knows better than left standing because nobody looked.

Sources

1. Vermicomposting life-cycle figures for Eisenia fetida: Biomedical Journal of Scientific & Technical Research, “Life Cycle of Vermicomposting Earthworms Eisenia fetida and Eudrilus eugeniae” — https://biomedres.us/pdfs/BJSTR.MS.ID.002015.pdf ↩
2. Romano D., Di Giovanni A., Pucciariello C., Stefanini C. (2023). “Turning earthworms into moonworms: Earthworms colonization of lunar regolith as a bioengineering approach supporting future crop growth in space.” Heliyon 9, e14683 — https://pmc.ncbi.nlm.nih.gov/articles/PMC10068126/ ↩
3. USDA Climate Hubs, “Non-Native Invasive Earthworms in the Midwest and Eastern United States” — https://www.climatehubs.usda.gov/hubs/northern-forests/topic/non-native-invasive-earthworms-midwest-and-eastern-united-states ↩
4. Stanford Report, “Earthworm invasion” (February 2024) — https://news.stanford.edu/stories/2024/02/earthworm-invasion ↩
5. Wikipedia, “Biosphere 2” — https://en.wikipedia.org/wiki/Biosphere_2 ↩
6. Wetterer J. K. et al. (1999). “Ecological Dominance by Paratrechina longicornis (Hymenoptera: Formicidae), an Invasive Tramp Ant, in Biosphere 2.” Florida Entomologist 82(3), 381–388 — https://www.jstor.org/stable/3496865 ↩