It’s been about two months since NASA astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko started a yearlong collaborative research project at the International Space Station. While in orbit, they’ll be testing how long-term space travel affects the human body, both physically and psychologically.
It's the longest trip a NASA astronaut has ever taken.
We already know quite a bit about the dangers of spending a long time in a zero-gravity environment. Because they don’t have to fight against gravity, muscles get weaker and bones lose their density.
But the real test here might be psychological. During his year in space, Kelly will be operating in tight quarters, with minimal bathing and limited human contact. Sleeping in space is also known to be difficult, and the majority of astronauts on the ISS take sleeping pills.
Over the next year, Kelly's body will be compared with that of his twin brother, Mark, a retired astronaut.
If all goes as expected, he'll return weak and fatigued — but just a slight bit taller than his brother.