Bone loss, changes in bone structure, muscle atrophy, and changes in the inner ear are just some of the suspected negative effect of spending extended periods o

Bone loss, changes in bone structure, muscle atrophy, and changes in the inner ear are just some of the suspected negative effect of spending extended periods of time in weaker gravity. They'd have to spend hours each day working out to counter those effects. Their day would primarily consist of sleep and working out, with a few hours of time for everything else. That doesn't make for a good televised program. On top of that, a minimum-energy launch window appears every two years and two months (or 780 days), making it way more realistic to send people on two year long missions.