NASA Astronaut Scott Kelly is on a mission to spend nearly one year in space, the longest mission of its kind by any American astronaut so far. But back here on Earth, his twin brother Captain Mark Kelly is also being studied by NASA for the same length of time. The goal is to learn exactly how space affects human health over extended periods, so that we can one day send astronauts on trips to Mars and beyond. And there's no better way to do that than by using identical twins! Would you be willing to spend a year under scientific observation? Watch our #WhatYouNeedToKnow video about the #yearinspace mission and learn what's involved in NASA's groundbreaking #twinstudy