Biosphere

Why Build a Biosphere for People?

At current estimates, it would cost around $22,000 to launch a medium pepperoni pizza to the International Space Station. For short space missions of less than two years it is cost effective to take along everything that is needed, as if one were embarking on a camping trip. But longer missions require that the crew grows their own food and that all the oxygen, water, and waste is recycled. The longer the mission away from Earth, the more complete the recycling has to be.

On the space shuttle and the International Space Station, everything that the astronauts and cosmonauts need is taken with them. To maintain a habitable environment within the spacecraft a physical-chemical life support system is used; equipment removes the carbon dioxide and other contaminants from the atmosphere and produces oxygen and water. These systems are efficient and compact, but they require that consumables be brought from Earth. For example, when the carbon dioxide is removed from the atmosphere it is vented to space or stored. This means that the oxygen contained in that carbon dioxide is no longer available for human consumption and that a source of oxygen must be supplied.

For a mission such as a long-term base on Mars, a life support system is required in which almost everything is recycled and reused and nothing is thrown away—a regenerative system. Systems that use living organisms to perform life support system functions are called bioregenerative life-support systems. Earth has such a bioregenerative system—the biosphere.

Biosphere 2

In Arizona, scientists built an artificial biosphere, called Biosphere 2. An eight-person crew lived inside the 1.28-hectare (3.15-acre) hermetically sealed structure for two years from 1991 to 1993. They produced their own food and recycled the atmosphere, water, and waste using a bioregenerative life support system.

Biosphere 2 had a mini rain forest, savanna, desert, marsh, and ocean, as well as a farm and a human habitat. The habitat housed the crew quarters, dining room, kitchen, medical facility, and an analytical laboratory for testing that the air was safe to breathe and that the water was safe to drink. There was also a machine shop for making and repairing equipment, such as water pumps, and the Command Room, with videoconferencing, Internet connections, phones, and a station to monitor the environment of each area in the biosphere.

Just as Earth's biosphere has cycles, so do bioregenerative life support systems. In Biosphere 2 the crew ate the same carbon molecules over and over again and breathed the same oxygen. Following is an example of how a water molecule might move through the biosphere.

After drinking a glass of water, a crew member excretes the water molecule as urine. The crew member flushes it into the wastewater treatment system, a specially designed marsh lagoon where plants and microbes work together to purify the water. Once the treatment cycle is complete, the water irrigates the farm crops. After soaking into the soil, the water molecule that the crew member drank is absorbed by the roots of a wheat plant and is later transpired through its leaves. The water molecule is now in the atmosphere, and after passing through a dehumidifying or condensing heat exchanger that maintains the temperature in the biosphere, the water is removed from the atmosphere and placed in a holding tank. A crew member preparing dinner goes into the kitchen and turns on the faucet. Out comes the water molecule, which becomes part of the evening soup. And so on it goes, around and around and around.

Biosphere 2 was the first attempt at a fully bioregenerative life support system. It demonstrated that such a system could be used to support human life on another planet. Someday people will inhabit other planets, and bioregenerative systems will play a key role in allowing that to happen.

SEE ALSO CLOSED ECOSYSTEMS (VOLUME 3); INTERNATIONAL SPACE STATION (VOLUMES 1 AND 3); LIVING IN SPACE (VOLUME 3); LIVING ON OTHER WORLDS (VOLUME 4); MARS BASES (VOLUME 4).

Jane Poynter

Bibliography

Eckart, Peter. "Bioregenerative Life Support Concepts." In Spaceflight Life Support and Biospherics. Torrance, CA: Microcosm Inc.; Dordrecht, Netherlands: Kluwer Academic, 1996.

Marino, Bruno D., and H. T. Odum. "Biosphere 2: Introduction and Research Progress." Ecological Engineering 13, nos. 1-4 (1999):4-14.

Purves, William K., Gordon H. Orians, and H. Craig Heller. Life: The Science of Biology, 6th ed. New York: W. H. Freeman, 2001.

Wieland, P. O. Living Together in Space: The Design and Operation of the Life Support Systems on the International Space Station. Marshall Space Flight Center, Huntsville AL: National Aeronautics and Space Administration, 1998.