Health effects of being in space

Astronauts on the moon are gleefully free of gravity as they bound across the lunar landscape.But low gravity presents serious health hazards to astronauts.
                                    When astronauts touch down on earth after a long stay in outer space,they go through an unearthly ordeal.Gravity is not their friend on earth for a while after a time period spent in space.
                                  Weightlessness presents serious health hazards during a stretch in space.
                                   Astronauts lose a lot of muscle mass in space.Astronauts work out daily in space and do weight training to counter the effects of low gravity.But without the resistance of gravity they still lose muscle mass quickly.
                                   When weary astronauts fall back from the sky after a long stretch in space they feel like a wet dish rag.
                                     Arteries get stiffer very quickly in space.According to an aging research lab,after six months spent in space ,the arteries grow stiffer by about 20 years in aging.
                                         Astronauts suffer a lot of muscle damage and artery damage in space.Scientists  are trying to manufacture artificial gravity to help astronauts.
                                         The cognitive and psychological effects of longer space travel is being heavily researched.
                                             As space travel takes astronauts deeper into the galaxy,extended exposure to solar radiation remains a potential problem.
                                               But space is opening up new frontiers for human travel and researchers are building up knowledge.