What Went Wrong?

As an attempt to create a balanced and self-sustaining replica of Earth’s ecosystems, Biosphere II was a miserable (and expensive) failure. Numerous problems plagued the crew almost from the very beginning. Of these, a mysterious loss of oxygen and widespread extinction were the most notable.
 

Catching Their Breath

Starting when the crew members were first sealed in, Biosphere II experienced a constant and puzzling decline in the percentage of oxygen in the atmosphere. It was initially hoped that the system was merely stabilizing itself, but as time passed it became increasingly clear the something was amiss. Not quite 18 months into the experiment, when oxygen levels dropped to the point where the crew could barely function, the outside managers decided to pump oxygen into the system so they could complete the full two years as planned.

Obviously, Biosphere II was not self-sustaining if outside oxygen had to be added in order for the crew to survive. The reasons behind this flaw in the project were not fully understood until some time later. As it turned out, the problem had more to do with carbon dioxide than with oxygen. Biosphere II’s soil, especially in the rain forest and savanna areas, is unusually rich in organic material. Microbes were metabolizing this material at an abnormally high rate, in the process of which they used up a lot of oxygen and produced a lot of carbon dioxide. The plants in Biosphere II should have been able to use this excess carbon dioxide to replace the oxygen through photosynthesis, except that another chemical reaction was also taking place.

A vast majority of Biosphere II was built out of concrete, which contains calcium hydroxide. Instead of being consumed by the plants to produce more oxygen, the excess carbon dioxide was reacting with calcium hydroxide in the concrete walls to form calcium carbonate and water.

Ca(OH)2 + CO2 --> CaCO3 + H2O

This hypothesis was confirmed when scientists tested the walls and found that they contained about ten times the amount of calcium carbonate on the inner surfaces as they did on the outer surfaces. All of the walls in Biosphere II are now coated with a protective layer, but oxygen levels continue to be somewhat problematic.
 

Walking a Tightrope

The designers of Biosphere II included a carefully chosen variety of plant, animal, and insect species. They anticipated that some species would not survive, but the eventual extinction rate was much higher than expected. Of the 25 small vertebrates with which the project began, only 6 did not die out by the mission's end. Almost all of the insect species went extinct, including those which had been included for the purpose of pollinating plants. This caused its own problems, since the plants could no longer propagate themselves.

At the same time, some species absolutely thrived in this man-made environment. Crazy ants, cockroaches, and katydids ran rampant, while certain vines (like morning glories) threatened to choke out every other kind of plant. The crew members were forced to put vast amounts of energy into simply maintaining their food crops. Biosphere II could not sustain a balanced ecosystem, and therefore failed to fulfill its goals.

Other Problems

Biosphere II's water systems became polluted with too many nutrients. The crew had to clean their water by running it over mats of algae, which they later dried and stored.

Also, as a symptom of further atmospheric imbalances, the level of dinitrogen oxide became dangerously high. At these levels, there was a risk of brain damage due to a reduction in the synthesis of vitamin B12.

And of course, there were inevitable disputes among the crew, as well as among those running the project from the outside.
 
 




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