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and the next revolution began. High up in the sky, ultraviolet radiation transformed some of this copious O₂ into O₃. (O₂, which contains two atoms of oxygen, is much more stable than O₃, with its three oxygen atoms.) This transformation created the ozone layer, which has intercepted the most aggressive radiations from the sun. (That is, until a life form called Thomas Midgley began tinkering with artificial chemical compounds). It was only due to this protective layer around the “sea of air”—as Alexander von Humboldt called the atmosphere—that new, more complex life forms could evolve. Approximately 420 million years ago life, in the form of plants, amphibians, reptiles and mammals, spread over the land.

Cyanobacteria not only provided these more complex life forms with the oxygen necessary to digest food effectively, they also passed on the molecular technology to produce it. According to a widely supported hypothesis, all multicellular plants came into existence by absorbing cyanobacteria and using them as interior “solar panels” to generate photosynthesis.¹³ Cyanobacteria thus became a component of each of the quarter million plant species known today, from cacti and dandelions to Sequoia trees. They have even stored a ration of their own genetic material. For these partners, it was a win-win situation. Cyanobacteria’s distant descendants are found everywhere plants grow, making the forest green. In addition, free-roaming cyanobacteria are still around. Two thousand contemporary species have been recorded to date. In the 1980s, American marine biologists Sallie W. Chisholm and Robert J. Olson, along with other collaborators, discovered a life form that had been previously overlooked. The organism was tiny but once it was detected, further research revealed that the cyanobacteria Prochlorococcus marinus was one of the most common organisms on earth and was probably one of the most widely spread types of picoplankton in the world.¹⁴

      Most people today are unaware of cyanobacteria except in unpleasant circumstances. If they are present in large quantities, due to fertilizer run-off and warm weather, they can produce substances that irritate human skin. But in places like Australia, cyanobacteria can also be admired: For millions of years, they have formed large colonies where their excretions produce stone-like structures, called stromatolites.

      No matter where you are or what you do, when you breathe to stay alive or enjoy time outside, when you eat vegetables or buy something made of iron or steel, you are inextricably linked to these revolutionaries.

      This extraordinary feat surely merits having a memorial erected in every modern city, in honor of the founders of the Club of Revolutionaries: “To the creators of the oxygen atmosphere, our planet’s protective shield, the plant world and iron deposits: In gratitude, humanity.”

      So far, that hasn’t happened. But in the step-by-step process of science, humanity is at least starting to discover how deeply connected we are, not only to our primate ancestors but also to a whole set of life forms that have made and continue to make earth livable. By doing research, humans have learned how bacteria, plants and animals have sustained life on earth and they have even begun doing experiments that attempt to recreate the conditions by which earth has stayed habitable.

      One of the first to do this kind of research was Joseph Priestley, a British chemist, theologian, philosopher and physicist. In 1772, he founded the discipline of earth modeling. Today, earth modelers have the advantage of gleaning reams of data from satellites and supercomputers. Priestley, who was interested in oxygen and who is regarded as one of its discoverers, worked with simpler technology. He trapped mice under a bell jar and watched what happened. After disposing of the inevitably dead animals several times, he was surprised when he observed that mice survived if he included a green, living plant, thus creating a tiny, enclosed ecosystem.

Priestly wrote the first ever description of photosynthesis, describing how animals and plants interact, in his inimitable prose: “These proofs of a partial restoration of air by plants in a state of vegetation, though in a confined and unnatural situation, cannot but render it highly probable, that the injury which is continually done to the atmosphere by the respiration of such a number of animals, and the putrefaction of such masses by both vegetable and animal matter, is, in part at least, repaired by the vegetable creation.”¹⁵

      With his bell jar, Priestley inspired a whole new research discipline: ecology, and later biospherics, the study of artificial, enclosed ecosystems. In 1875, Austrian geologist Eduard Suess created the term “biosphere” to describe the space used by living organisms. A few decades later, the Russian geologist Vladimir Vernadsky expanded this concept when he realized that the biosphere is not only inhabited by living organisms but has also been shaped by them. Vernadsky demonstrated how humans are existentially a part of the biosphere.

      When both the USA and the USSR were in a race to reach the moon and conquer the vastness of space, Russian scientist Yevgeny Shepelev confined himself in the smallest possible artificial ecosystem, assigning himself the role of Joseph Priestley’s mice.

In 1962, he climbed into a small, airtight metal container at the Institute of Biomedical Problems in Moscow. When he sealed the door behind him, he was not alone: he shared the cramped space with forty-five liters of green algae, of the genus Chlorella. His plan was for the algae to supply him with the oxygen he needed to survive. This forty-two-year-old Russian was the first person to make himself completely dependent on a bucket of plants.¹⁶

      Shepelev grew up with eight siblings in impoverished circumstances. He discovered his love of science very early in life and managed to be accepted into the scientific youth club at the Moscow Zoological Gardens. He then studied medicine and devoted himself to a broader subject: how life could survive in outer space. He wanted his containers to show that cities of the future could be built and maintained, on other planets. Thus, the Soviet Union would colonize outer space before the capitalist West.

Shepelev’s first experiment lasted a mere twenty-four hours. When a colleague opened the door of the container, he complained of being hit by a rotting smell. Its occupant was dazed and confused, his thought processes befuddled by his own exhaled gases. Yet, Shepelev had actually managed to live off the oxygen produced by his algae.¹⁷

      In the Siberian city of Krasnoyarsk, other scientists were undertaking similar, strictly confidential research. In 1972 three scientists managed to survive for half a year in BIOS-3, an artificial ecosystem, without external supplies of water and oxygen. By the end of the 1980s, Russian scientists succeeded in producing three quarters of the food they needed, in “closed” systems. Since a diet consisting entirely of algae made them feel bad tempered, they started growing cucumbers, tomatoes, potatoes, peas and other container plants, and even created a new type of soil that was dubbed “soil-similar substrate.”

In time, the Russians became more daring. When the political climate in the Soviet Union began to change in the mid-1980s, they even started doing tests to measure environmental problems that, by definition, did not exist in a “socialist” society, even though everyday Soviet life was full of them. The scientists pumped pollutants into containers to investigate the effects. “The ability to buffer these kinds of substances and transform them is limited,” stated a terse summary in one report. What was meant by this was clear: ecosystems can handle stress for a long time but under continual stress they will eventually collapse.¹⁸

While the Russian experiments were being carried out in secrecy, a group of scientists and idealists in the USA, meanwhile, were working on a significantly more complicated artificial ecosystem. In 1991, with great fanfare, Biosphere 2 was inaugurated by John P. Allen, a maverick with a background in mining and metallurgy, who had a strong personal vision that Biosphere 1, planet Earth, was in big trouble. Allen once held the rights to a coal seam worth a fortune, but according to him, the expected course of his life completely changed after a transformative

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