NEW YORK, N..Y (WPVI) -- New results from a study of astronaut twins show space changes the body - and it doesn't completely return to normal back on earth.
NASA says Scott Kelly's carotid artery thickened, as did his retinas, and the microbes in his intestinal tract changed compared to his identical brother Mark during 340 days on the International Space Station.
He also had reduced cognitive abilities and a structural change at the ends of chromosomes called telomeres. But it did not alter or mutate his DNA.
NASA grouped the changes into low-, mid-level, and high-risk groups.
Body mass and microbiome were considered low-risk, while shifts in collagen regulation and blood vessel fluid management were mid-level,
Although the majority of changes reversed back on earth, 6 months later, Scott's thinking patterns were still off.
The much-anticipated study reveals areas that may require countermeasures or safeguards when preparing for longer space missions or missions to deep space, like Mars.
The study, which includes the work of 84 scientists who made up 10 teams from 12 universities in eight states, all studying different aspects of the human body in space, was published Thursday in the journal Science.
Coincidentally, the results are being released just in time for the 58th anniversary of the first manned spaceflight by Soviet cosmonaut Yuri Gagarin.
Lessons from astronaut twins shed light on space effects