https://apnews.com/78089472d2814b098798ad2ceb2e99b9

WASHINGTON (AP) — From his eyes to his immune system, astronaut Scott Kelly's body sometimes reacted strangely to nearly a year in orbit, at least compared to his Earth-bound identical twin — but newly published research shows nothing that would cancel even longer space treks, like to Mars.

The good news: Kelly largely bounced back after returning home, say scientists who released final results from NASA's "twins study," a never-before opportunity to track the biological consequences of spaceflight in genetic doubles.