NASA is preparing to send humans to Mars sometime in the 2030s. The 3-year mission will expose astronauts to a long period of microgravity, which will cause them to lose bone mass. But now, scientists report transgenic lettuce that produces a bone-stimulating hormone. Someday, astronauts could grow the lettuce in space and help guard against bone loss—simply by eating a big bowl of salad. In addition, the lettuce might help stave off osteoporosis in resource-limited areas here on Earth, the researchers say.