Space Seeds Return to Earth

Plants in space won't only be a source of food -- they'll have other jobs to do as well, playing a critical role in cutting-edge life support systems.

On Earth, photosynthetic organisms like plants and algae provide a natural life support system for the planet's many life forms. Plants and algae use energy from light to split water molecules into hydrogen and oxygen. Then they combine the hydrogen with carbon dioxide to make sugars, which serve as food. Oxygen is released into the air as "waste." This serves as a perfect compliment to other life forms such as animals and fungi, which use the oxygen and respire carbon dioxide.

Taking a cue from nature, scientists at NASA's Johnson Space Centre and Kennedy Space Centre are pioneering next-generation "bioregenerative" life support systems, which use plants rather than machines to perform the chemistry of life support.

Not only do plants release precious oxygen, they can also help recycle drinking water. After some processing, nutrient-rich waste-water can be used to water and fertilise the plants. Much of the water absorbed by the roots will evaporate from the leaves as pure water vapour. Condensing this water vapour. out of the air creates virtually pure, distilled water that can be used for drinking.

While elegant in theory, the fine details of such a system must be worked out before plants and people can live in a successful space-symbiosis. Learning to grow many generations of plants in space is an early step toward that goal.

Many research teams at NASA and NASA-sponsored university projects are experimenting with plant growth for space missions, but Zhou's team is the only one at the moment that's actually growing plants in space from seed to seed.

"What WCSAR and industry are doing is rather unique," Zhou says. But researchers hope it will soon be common. Fast-growing plants that thrive from generation to generation in orbit will surely produce the seeds from which human exploration of space will spring.