The space explorer's body

His gut microbiome showed altered bacterial proportions, although the overall bacterial diversity was intact.

Several proteins also changed during the spaceflight.

• Elevated levels of collagen, a structural protein was seen in his urine. Looking at this measure along with physiological changes—like those observed in Scott’s eyeballs and vascular system—could be a sign that the body was restructuring.
• Researchers also observed heightened levels of aquaporin 2, a protein that tends to be a marker of dehydration.