Astronauts have to be very careful when they're in space, explains Harry Whelan, a neurologist at the Medical College of Wisconsin in Milwaukee. "Minor injuries typically don't heal until they land," he says. The reason for this is not well understood, but a cell's mitochondria--its energy sources--don't function as efficiently in zero gravity, and this leads to a variety of health risks.

One way to boost the efficiency of mitochondria is to irradiate them with red and infrared light, which stimulates them to produce key chemicals called cytochromes. The question is how to generate the light.

"There's been a lot of work done with lasers, but they're too expensive and too problematic," says Ronald Ignatius, the president of Wisconsin-based engineering firm Quantum Devices.

So with NASA's help, Quantum Devices has developed highly efficient LEDs that produce the required wavelengths, also letting designers create devices large enough to bathe the whole area with light. When Whelan illuminated cultured cells with light from the LEDs, he discovered that they grew significantly better. "We have shown that fibroblasts and muscle cells grow five times faster," he says. Clinical trials are also under way.

Combined with treatment in high- pressure oxygen chambers and perhaps various growth-inducing chemicals, Whelan hopes that the LED-based therapy will provide a way for astronauts to heal their wounds, and even prevent muscle and bone loss during extended spaceflight.

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