Research teams involved in NASA’s groundbreaking Twins Study have confirmed their preliminary findings, with a full paper explaining the results expected later this year.

The Twins Study saw researchers monitor astronaut Scott Kelly on the International Space Station (ISS) from March 2016 to March 2017, in comparison to his twin brother Mark who remained on Earth.

This provided a unique opportunity to see the effects of spaceflight on a human. Scott spent a year on the ISS as part of the Year in Space mission, together with Russian cosmonaut Mikhail Kornienko. Alongside the Twins Study, it’s hoped this mission will help prepare astronauts for the three-year return trip to Mars.

In January this year, the 10 investigators involved in the Twins Study confirmed their preliminary findings from last year, and also added some findings that have been made since Scott returned to Earth. You can read a detailed rundown of the research here, but we’ll run through some of the most interesting findings below.

Susan Bailey from Colorado State University found that Scott’s telomeres, the “caps” on the end of chromosomes, increased in length while he was in space. But within 48 hours of landing they shortened, and later returned to the length they were before his mission. Mark’s, on the other hand, remained the same.

The cause may be the rigorous exercise Scott had to go through on the station to maintain bone and muscle mass. Another possibility, backed up by research from Scott Smith of NASA’s Johnson Space Center, is that Scott’s healthier diet on the ISS may have played a part. This may also have contributed to a drop in body mass while in space.

A positive result from Emmanuel Mignot of Stanford University found that being in space did not affect Scott’s immune system. He gave both Scott and Mark a flu vaccine before, during, and after Scott’s mission, and found both had an increased immune cell response. That’s good news for protecting astronauts from disease on long-duration missions.

It was also discovered that 93 percent of Scott’s genes returned to normal after he landed. However, the 7 percent of genes that did not suggest that there are some longer-term changes from prolonged spaceflight linked to DNA repair, bone formation, and more.

Later this year, the team will release their joint paper detailing the findings, alongside a series of smaller papers in related areas. Until then, we are just starting to get a handle on exactly what spaceflight does to the human body – and how that might affect astronauts going to Mars or elsewhere in the future.