Wasnt Until Scott News Today : Breaking News, Live Updates & Top Stories | Vimarsana

Researchers found there had been a change in seven percent of his gene expression. despite this change, scott and mark are still very much identical twins and now retired astronauts whose greatest legacy may be in helping all of us understand what our bodies are truly capable of. >> just incredible brothers, incredible family, too. the study fundamentally is about mars. that's what you find out, that mars would be three years to go and come back. why are they testing someone like scott to see how he lasts for a year in space? it gives you an answer of how three years might go. after a year or ...

That environmental effects us on a genetic level and what it means. >> reporter: for the twin study, nasa closely monitored everything, scott's diet, movements, vitals on board the international space station and the same for mark back on earth. >> i got the impression there were some people that were surprised we said yes. >> was there any reservation on your part? >> no. not really. overall, i mean, i think this is important research. i think what nasa does i'm 100% behind nasa's mission. we both flew in space four times. we are really committed to this and committed to the science. >> scott...

Scott and mark kelly truly remarkable and rare brothers. they simultaneously served as astronauts making them the perfect duo to understand what prolonged space travel does to the human body. in order to try to answer that question, scott went up to space for a year while mark stayed home on earth. how much did the family worry for you when you were up in space? >> you know, i think our mother and father get pretty freaked out especially on launch day. more for me because they like me better. >> reporter: it wasn't until scott's fourth and final trip to space that this revolutionary scientific...