Astronauts experience many detrimental changes in their bodies when they leave the 1g environment of Earth and travel in microgravity (0g). Such changes including loss of bone mass and muscle atrophy. We know a great deal about life in 0g thanks to numerous missions aboard the shuttles and the International Space Station; but now scientists are starting to wonder what will happen to humans living in environments like Mars, which experience a fraction of Earth’s gravity. At .38g, is Mars gravity enough to keep human explorers healthy? Will they be able to readapt when they return to Earth?