In a plant growth chamber in the Kennedy Space Center Space Life Sciences Lab, plant physiologist Ray Wheeler checks crops being grown using hydroponic techniques, and subjected to different types of light, and CO2 concentrations, and temperatures. (Photo credit: NASA Kennedy Space Center)

No question about it - plants are vital to our existence here on earth. They provide us with the essentials of food, oxygen, and shelter. But have you ever stopped to think about how these benefits would translate beyond our planet?

Traveling with plants is not a new concept. Early explorers and colonists frequently packed cuttings and seeds from their favorite green friends on their journeys. Growing plants from their native lands provided them with a source food and medicine, and also helped alleviate another common ailment - homesickness. Plants can provide similar benefits to astronauts. Here’s how:

Food: Currently NASA compares the food system for astronauts to a picnic – they have to pack everything they need and take it with them. But as the length of space visits grows – as we begin using the International Space Station, and strive to reach Mars – space travelers will need a renewable food source. Besides, fresh produce adds to the variety and texture of meals and breaks up the monotony of eating prepackaged foods.

Attitude: The psychological benefits of plants are hard to measure, but they are clearly evident (see What Have Plants Done for You Lately?). Just as green space is important to the health and well-being of urban dwellers, astronauts who are surrounded by a totally synthetic, cramped, metal and plastic environment can find relaxation and pleasure in the presence of plants. Experiments with plants are incorporated into missions not only to advance knowledge and technology, but also to provide astronauts with a little connection to the green, living Earth they’ve left behind.

Here’s how plants can fulfill the needs of space travelers:

Air: Plants use carbon dioxide and produce oxygen through the process of photosynthesis, and this could improve the air quality inside spacecraft. NASA is also exploring plants’ ability to reduce other airborne contaminants. For more information, visit Common Indoor Plants Help Reduce Air Pollution.

Water Purification: Pick up a gallon of water, and you realize that transporting enough to sustain astronauts for more than a few days is a challenge – and an expensive one at that, estimated at $22,000 per kilogram! It will be very beneficial if researchers can come up with a practical way to reuse water on space missions. Plants can fit into this plan because they give off pure water via respiration. Scientists are developing techniques to use astronauts’ wastewater, such as that used for washing, to water plants, and then recapture the clean water produced during transpiration.

Recycling Waste: Researchers are investigating ways to recycle/compost human waste and inedible plant matter to provide nutrients to plants. This is an important element for creating a self-contained ecosystem.

How Does an Astronaut's Garden Grow?

There is no argument among space scientists about the benefits of “green astronauts” – it’s just a matter of finding efficient and successful ways to grow plants in space. They have the same needs as those grown here on Earth: water, air, light, nutrients, and a place to grow. The challenge is finding ways to meet these needs in the cosmic environment. The small area within a spacecraft and the need to keep weight to a minimum mean that space gardens must differ greatly from their earthly counterparts. Some considerations include:

Water: As mentioned above, taking water into space has its serious down side, so astronauts can only take what they need to survive. Water-thrifty plants that can thrive on recycled waste would be ideal. It’s also important to figure out how to deliver water to plants because lack of gravity means that traditional watering isn’t an option -- the setup will have to supply water directly to the growing medium.

Air: Astronauts provide the carbon dioxide plants need for photosynthesis, but since air does not circulate naturally in space the composition of air can be a problem. The oxygen released by plants during photosynthesis can cluster around the plants and lead to plant death unless fans are used to keep the air moving. Plus, there are other gases inside spacecraft that must be filtered out or they'll harm the plants.

Light: In space, light for plants will have to come from artificial sources that must be extremely energy efficient to avoid overtaxing of spacecraft resources.

Nutrients: The nutrients plants need for proper growth have to be present in the growing medium. As mentioned above, scientists are investigating ways to recycle human and plant waste into a nutrient source.

“Space” to Grow: Because of their weight, traditional garden soil and potting mix won’t work in space. Scientists are experimenting with alternative media, such as gels and soilless mixes, and techniques such as hydroponics to create a “place” for plants. The gravity-free environment adds to the challenge by changing the way roots, shoots, and soil water behave, so the design of growing containers must help plants overcome the effects of zero gravity.

With these considerations in mind, scientists are taking two different approaches: creating growing systems to provide acceptable environmental conditions, and creating plants adapted to extraterrestrial environments.

Botanists, horticulturists, and agriculture engineers at private and public institutions around the country are working to create and test growing systems suitable for space travel. Here are a few examples:

Bioserve Plant Growth Chamber
VEGGIE, the Deployable Vegetable System
Greenhouses for Mars

Designing Special Plants for Space

Ideal space plants are short, grow in low light, have few inedible parts, result in a quick and reliable harvest, and resist disease. Although existing plants are certainly being tested for their compatibility, researchers are also using breeding and genetic engineering techniques to make new varieties that are optimal for space farming. Check out the following articles:

Prozac for Plants
Designer Plants on Mars

Participate in Research!
Since it’s inception, NASA has worked to engage students in space-related experiments. In December 2006, a new seed germination study was launched in a partnership with BioServe Space Technologies Center at the University of Colorado at Boulder. Visit the Web site for more details and contact information to inquire about future opportunities.

Curriculum
Adventures of the Agronauts - for grade 3
NASA's Investigating Plants in Space curriculum - for grades 5-12 (PDF document)
International Space Station's Farming in Space - for grades 5-12
Space Agriculture in the Classroom - for grades 9-12

Plant Tropism Lessons
NASA's Plants in Space Lesson
Why Do Plants Grow Upward? (NASA)

NASA Explores Lessons
These online lessons offer background info and lessons for three separate grade groups: K-4, 5-8, and 9-12. Here are a few we’ve hand-picked:
Plants in Space
Off Planet Plants
Plants Can Recycle

Additional Backgound Resources
Leafy Green Astronauts
Plants in Space
Growing Plants Without Gravity
Growing Food for Space Travelers
NASA Plant Study