(This article is based on a chapter in my book Strange Encounters: Adventures of a Renegade Naturalist)
If we are going to Mars and hope to settle there, we need to develop reliable ecological life-support systems that provide food, oxygen and water, and recycle wastes. Such a system doesn’t exist, but I have tried to help develop one.
Back one day in the early 1970s, I came across an article about a plan to build a giant space station orbiting the Earth, one that would hold 10,000 people who would live in a kind of Garden of Eden. The space station was to be shaped like a giant donut (what mathematicians call a torus), and the illustration in the article showed a cut-away view of life in the donut, making the huge construction appear as a horn of plenty. Inside, people floated through the air. There was an equivalent of gravity created by the slow rotation of the torus, but the force would be slight enough so that you could fly. People flew and landed on plants, like small birds, feeding on fruits.
The author, Jerry O’Neill, a professor of engineering at Princeton University, wrote in the article that the biological problems were simple. All you had to do, he wrote, was sterilize everything and get it up there.
Space travel had been one of my longest fascinations. When I was five years old, I had cut out circles of different sizes to represent the sun and the nine planets of our solar system. I drew and cut out paper space ships and flew them from planet to planet. The necessities required to keep life going in a spaceship seemed clear to me then – water, oxygen, food, a place for waste, a way to recycle. I spent hours designing spaceships, trying to decide the best places to store oxygen, water, food, and have room for people.
In the 1970s, Jerry O’Neill was getting quite a bit of publicity about his idea. There was a special television program that showed him flying away in his private airplane, discussing space stations. And some people were suggesting that the solution to the human population problem was to place all the excess people in O’Neill-like space stations.
So reading Jerry O’Neill’s article I thought that he had missed some major points. Here was an engineer saying it would all be simple up in space. I didn’t believe it. I met with O’Neill and raised one of the simplest problems, balancing the concentration of carbon dioxide and oxygen in the atmosphere. He said “I can see where the carbon dioxide comes from, but where does the oxygen come from?” He was planning an ecological life supporting system in space and didn’t even know about photosynthesis.
I discussed this with my friend and colleague, Lynn Margules, a biologist famous for her work on early life and for her contributions to the idea that became known as the Gaia Hypothesis. We wrote a brief article discussing the challenges that confronted the life support system for such a floating donut filled with people. Lynn took it on a trip to Europe and returned with the signatures of about twenty other scientists, and we got in published in an obscure scientific magazine and one popular magazine.
As a result, the National Academy of Sciences Space Science Board asked me if I be willing to conduct a summer study about the ecological problems associated with long-term space travel. With my lifelong fascination with space travel, it was an offer I could not turndown. I decided that the path to this study was to find the most imaginative people I could, and the broadest thinking. I formed a working committee of five: Harold Morowitz, a biophysicist who had written about ecology, understood biochemistry as well as biophysics, knew a lot of mathematics and had written about the limits that energy placed on life and about the origin of life; Larry Slobodkin, an ecologist famous not only for his work but for his breadth of knowledge of many subjects and his incredible imagination; Ecologist Bassett Maguire, who had created and studied tiny closed ecosystems; Mathematician Berrien Moore, who had decided to shift his work to ecology; and microbiologist Stephen Golubeck.
We five assembled on a beautiful summer morning in Snow Mass, Colorado, where the Space Science board was meeting. During our brief walks away from our discussions, we saw sublime mountains rising in the distance, where forests formed deep green streaks as if their color had slid down the slopes. We felt the soft wind from the mountains and smell the sweet scents of the fir trees. Squirrels chattered and birds called outside. Snow Mass abounded with life; the air was a pleasure to breathe in; it was about as different from an enclosed donut shaped orbiting space station as I could imagine.
The first time we met, Larry Slobodkin, a tall and heavy-set man with a long beard, squeezed himself into one of the chairs in a small room. He said: “ Imagine this space station. It’s going to have a control center full of knobs and dials. There will be people manning that control center. They will read the dials and adjust the knobs. Now the first thing they will want to have is a dial that tells them that the whole system is about to fail.”
“You mean sort of like the oil pressure gauge on a car,” I said.
“Exactly,” said Larry, “or when the donut will get a flat tire, too.”
We began to talk about what this dial might be. What was the equivalent of an oil pressure gauge for a huge, closed ecosystem that was supposed to support people?
Harold Morowitz began to draw diagrams on pads of paper. He drew boxes and arrows representing the flow and storage of chemical elements needed by living things, and how these might move around the space station. We talked throughout the day about Larry’s gauge without getting any kind of answer.
“You see, if it was an automobile that had designed ourselves from start to finish, we would know what variables were crucial,” said Harold, “but we didn’t invent life and we don’t understand ecosystems, so we don’t really know what that gauge would be like.”
We realized that the only way to approach the question of what the dial would be was to think about how to create a scientific theory for ecological systems, which did not exist. This was the beginning of a long series of conversations that lasted over five years and produced a number of scientific papers.
Our first summer’s thoughts seemed to strike a cord with NASA, which began to support some research by its scientists at some of its eight research facilities on the characteristics of such a space station. But it was the engineers, not the biologists, who seemed to take the most interest. They issued a report that compared an ecological life support system with a conventional one.
In a conventional space vehicle, everything was brought along. Water was obtained from fuel cells that “burned” hydrogen with oxygen and created electricity. The waste was pure water. Carbon dioxide was recycled directly through a chemical process. Food was dried and stored on board. It was like a long picnic rather than living at home on a farm. The weight of a conventional system depended on the length of the space voyage. Each day required the same weight of materials, so a week would require seven times the weight of supplies as one day, a year would require 52 times a week supply, and so forth.
The engineers drew a graph showing the weight required versus the length of the voyage. The weight of the conventional system increased by the same amount for every day longer the voyage took. In contrast, the ecological life support system weighed the same for any length of voyage. It was very heavy, and it was heavy from the beginning.
So there was a trade-off. As long as the weight of all the food, water and gases necessary for life was less to carry than the weight of the ecological life-support system, it made more sense to use a conventional system. Picnicking in space made sense for short trips more than creating a homestead, just as it did down here on Earth. The cross-over point, when it became more weight and energy efficient to use an ecological life support system, was when the voyage was long enough so that all the picnic supplies required if one carried them equaled the weight of the ecological self-contained system. For any longer voyage, the ecological system would be more efficient.
But the engineer also pointed out that you did not have to make everything. There could be a hybrid system. For example, it made sense to carry vitamins, since these weigh little but are hard to make and it would be difficult to maintain all the life forms necessary to make enough vitamins. The work continued for a number of years, well into the mid 1980s, and the space engineers explored this tradeoff in considerable detail. How much stuff was worth bringing along versus making on the spacecraft? They considered many possibilities. They concluded that a compact source of food heavy in protein and fat would greatly reduce the weight of the ecological system, and that the ideal food for this purpose was peanut butter. So lesson of the years of work that began when I came across Gerry O’Neill’s article about flying donuts with 10,000 residents, was: if you are going on a long space voyage and plan to have picnics, don’t forget the peanut butter.
This was about the time the funding for this work petered out. Clearly, the problem was more complicated than peanut butter in space, but the design of a reliable ecological life-support system for long-term space travel has not, even in 2013, been developed. I'm still fascinated by space travel and continue think about what the life-support system might be like.
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