The Twins Study went a step further, including surveying the brothers' genomes and collecting data on Scott and Mark's physical and psychological health. In the case of Scott, some of the changes to his body disappeared only a few hours or days after landing, while some remained after six months. Here are some of the major new findings:
Scott's telomeres — or the ends of chromosomes that shorten as people get older — got a lot longer in space. This finding was known in 2017, but investigators confirmed it and also discovered that most of the telomeres got shorter again within two days of Scott's landing.
About 7 percent of Scott's genes may have longer-term changes in expression after spaceflight, in areas such as DNA repair, the immune system, how bones are formed, hypoxia (an oxygen deficiency in the tissues) and hypercapnia (excessive carbon dioxide in the bloodstream). The other 93 percent of his genes quickly returned to normal.
Scott had no significant cognitive performance decline in space after one year, compared with Mark or with typical astronauts who fly a six-month mission. Investigators did, however, see pronounced decreases in Scott's cognitive speed and accuracy after he landed. This might have happened because of "re-exposure and adjustment to Earth’s gravity, and the busy schedule that enveloped Scott after his mission," NASA officials said.
The researchers also saw that spaceflight is linked with nutrient shifts, oxygen deprivation stress and more inflammation. They gathered the evidence after looking at "large numbers" of proteins (chains of amino acids), cytokines (substances secreted by cells in the immune system) and metabolites (substances related to metabolism) in Scott's body.
