Space exploration, Mars, and the nervous system.

When human beings venture back to the moon and then on to Mars in the coming decade or so, we will be riding on the accumulated data and experience from approximately 50 years of manned space exploration. Virtually every organ system functions differently in the absence of gravity, and some of these changes are maladaptive. From a biologic perspective, long duration spaceflight beyond low Earth orbit presents many unique challenges. Astronauts traveling to Mars will live in the absence of gravity for more than 1 year en route and will have to transition between weightlessness and planetary gravitational forces at the beginning, middle, and end of the mission. We discuss some of what is known about the effects of spaceflight on nervous system function, with emphasis on the neuromuscular and vestibular systems because success of a Mars mission will depend on their proper functioning.