In October 2015, the NASA Office of Inspector General issued a health hazards report related to space exploration, including a human mission to Mars. A fundamental step in overcoming this challenge is trying to understand the effects and impact of long-term space travel on the human body. This question requires input from the physical and biological sciences and has now become the greatest challenge (other than funding) facing human space exploration.

In recent years there has been an increase in research on the issue of how humans can survive and work in space for extended and possibly indefinite periods of time. The engineering problems associated with leaving Earth and developing space propulsion systems have been examined for over a century, and millions of hours of research have been spent on them. Overall, NASA refers to the various deleterious effects of spaceflight on the human body by the acronym RIDGE (i.e., 'space radiation, isolation and confinement, distance from Earth, gravity fields, and hostile and closed environments').

Additional symptoms include fluid redistribution (causing the ' moon-face' appearance typical in pictures of astronauts experiencing weightlessness), loss of body mass, nasal congestion, sleep disturbance, and excess flatulence. Other significant effects include a slowing of cardiovascular system functions, decreased production of red blood cells (space anemia), balance disorders, eyesight disorders and changes in the immune system. Significant adverse effects of long-term weightlessness include muscle atrophy and deterioration of the skeleton ( spaceflight osteopenia). Venturing into the environment of space can have negative effects on the human body. American Astronaut Marsha Ivins demonstrates the effects of microgravity on her hair in space For the general study, see Bioastronautics. This article is about the medical consequences of spaceflight on humans.

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