Scott Kelly spent a year on the ISS while his twin brother Mark stayed on the ground for comparison studies. https://www.nasa.gov/twins-study https://www.nasa.

Scott Kelly spent a year on the ISS while his twin brother Mark stayed on the ground for comparison studies. https://www.nasa.gov/twins-study https://www.nasa.gov/twins-study https://en.m.wikipedia.org/wiki/Scott_Kelly_(astronaut) https://en.m.wikipedia.org/wiki/Scott_Kelly_(astronaut)