NASA Twin Study: Space Alters Gene Activity and Telomeres, Most Changes Rebound

NASA's twin study compared Scott Kelly in orbit with his Earthbound brother Mark to isolate space effects; researchers found rapid gene-expression shifts and heightened immune activity in Scott, with telomere elongation in space that shortened after return; radiation caused more DNA damage and repair signals in Scott than Mark; by six to eight months post-mission, most gene-expression changes had reverted, indicating reversibility but signaling potential long-term risks for future long-duration missions such as cardiovascular strain, vision problems, and cancer risk.