By definition, a plant is a living thing that produces its own food through photosynthesis. This process uses carbon dioxide and water. Trapping light from the Sun, plants are able to change sunlight’s energy into useable chemical energy. Not only is chemical energy produced, but oxygen is a by-product of photosynthesis. Plants are essential to the balance of life on Earth … and to life, as we know it, on other planets.

Plants may play an important part in NASA’s Vision for Space Exploration. When human beings establish permanent bases on the moon or Mars, they will continue to need food, water, and air, but because those items aren’t widely available on other planets, keeping a ready supply on hand will be a challenge.

"The solution to extended life support," Knott says, "is simpler than you might think. Rather than packing the Orbiter full of precooked meals and other vital supplies, some day soon the cargo might be full of seedlings and gardening supplies."

"People have several basic needs: oxygen, water, food, and waste removal. "Growing plants in a closed system takes care of all those concerns," Knott says.

After all, Earth is a closed system, even though we can’t see the walls of the system. When human beings consume food, it’s oxidized and carbon dioxide (CO₂) is given off as waste. Plants use the CO₂, along with water and minerals, to generate new food and give off more oxygen.

"Plants also help with other human conditions," Knott says. Plants can take wastewater and filter out products and organisms that are harmful to people, leaving clean water in their place. They also provide an aesthetically pleasing and emotionally comforting atmosphere. "Astronauts enjoy working with plants," he says. "It brings a bit of home along with them into space."

Scientists at NASA’s Ames Research Center, Johnson Space Center, and Kennedy Space Center have been working out the details of growing plants in space to help human beings live independently of the Earth. The Advanced Life Systems (ALS) program has produced encouraging results.

"We've been pleased with the findings so far," says Ray Wheeler, plant physiologist at KSC. "Plants are a viable option for life support. They’re reliable and predictable if their environmental needs are carefully controlled; the plants themselves rarely malfunction. Most problems we encounter are because of a poorly functioning pump or a computer glitch, not because of a plant problem. This news is all very encouraging."

Some fundamental scientific studies are being conducted with plants on the Space Shuttle and the International Space Station (ISS) because a space environment helps show the effects of low gravity on plant growth. But these studies are typically too short to thoroughly explore the full extent of crop growth and development for the ALS program.

"ALS will need to follow a plant’s entire growth cycle to assess the crop yields," Wheeler says. "Even when we choose plants with short life cycles to optimize growth and production, such as salad crops like lettuce, it takes a while for the entire cycle to be complete. Small plantings could make a significant contribution to diversifying the crew diet, even on the ISS, but a system with plants would be more economically feasible for a space colony or long-duration trip to Mars."

The plants chosen would be ones that produce the most edible materials with the least waste, grow the quickest, and are the easiest to maintain. We may not need soil to grow these plants because hydroponics methods have been used successfully for years, but even hydroponics has its limits in space.

"You can’t have open containers of water to grow plants in," says Knott. "In microgravity, water wouldn't stay where you put it. Instead, astronauts would likely use water-soaked materials, including cloth strips, to provide the moisture to the plants."

Light is another significant factor in growing plants in space. On the Space Shuttle, there are extended periods of darkness, and in a space colony there could be even longer times of darkness. Artificial lighting requires thousands of watts of electricity to grow plants, and even natural light needs to be collected, stored, and channeled efficiently. Scientists are experimenting with light-emitting diodes as a form of light that is energy efficient as well as inexpensive to use.

"Controlled farming in space is feasible, and now we just have to pursue it, develop it, and put it into action," says Knott. "If we’re ever going to be independent of Earth, plants and photosynthesis are the ways to do it."

KSNN thanks NASAexplores as a source of information. Visit NASAexplores. For more information about this topic and additional teaching resources go to (http://www.nasaexplores.com).