worms seem like strange animals to send to the International Space Station. It's not like astronauts are going to take time off to go fishing and need to bait their hooks. So why send worms? Believe it or not, scientists are using a microscopic worm, Caenorhabditis elegans, to study the effects of weightlessness on muscle mass. We have known for decades that long space flights lead to muscle atrophy, or wasting. Scientists have suspected this is due to differences in hormone and steroid blood levels as well as a decrease in exercise that affects muscle fibers directly. Astronauts exercise, but can still lose up to 60% of their muscle mass during a mission. So scientists are looking for genes controlling muscle building to see if they can figure out a way to keep muscles intact in zero gravity. That is where C. elegans comes in. These worms that normally live in soil and compost suffer from muscle atrophy under many of the same conditions that people do. Not only that, they are easy to transport, reproduce quickly and have a small genome that's already been sequenced. Since the worms share many genes with humans, scientists hope to discover which genes can help prevent muscle fibers from being degraded and lost. A shuttle mission scheduled for October 2009 will be the fourth time worms have traveled to space. They will spend two weeks in the Japanese Kibo laboratory before they return to earth. Scientists are hopeful that this trip will reveal the secrets of controlling muscle atrophy. If it does, the knowledge will not only help astronauts, it will be able to help patients on earth who are bedridden or immobilized.