Even short trips to space can change an astronaut’s biology

Only about 600 people have ever traveled to space. The vast majority of astronauts over the past six decades have been middle-aged men on short-duration missions of fewer than 20 days.

Today, with private, commercial and multinational spaceflight providers and flyers entering the market, we are witnessing a new era of human spaceflight. Missions have ranged from minutes, hours and days to months.

As humanity looks ahead to returning to the Moon over the coming decade, space exploration missions will be much longer...