Retired Astronaut Scott Kelly Reveals Physical Setbacks From Time in Space Kelly says his year in space took a physical toll.

 -- Scott Kelly, who recently returned to Earth after almost a year in space, plans to share more about the toll his time in orbit has taken on his body.

“I lost bone mass, my muscles atrophied, and my blood redistributed itself in my body, which strained my heart,” he said in a news release about his forthcoming memoir, “Endurance: My Year in Space and Our Journey to Mars,” which publisher Knopf said Wednesday will be released in November 2017.

Kelly was aboard the International Space Station for 340 consecutive days, a record for the most time spent in space by a U.S. citizen. Nine days after his mission ended last month, the 52-year-old announced his retirement.

In the release from Knopf about the book, Kelly says, “Every day, I was exposed to ten times the radiation of a person on Earth, which will increase my risk of a fatal cancer for the rest of my life. Not to mention the psychological stress, which is harder to quantify and perhaps as damaging."

But despite the physical setbacks Kelly describes, the veteran Navy pilot will also detail in the book his faith in space exploration and his desire to see both government-backed and private space travel, according to Knopf.

The NASA project on which Kelly worked aimed to observe the long-term effects of spaceflight on the human body. Kelly underwent medical experiments, as did his identical twin brother, Mark Kelly, who was on Earth at the time, serving as a control subject.

Kelly shared his enthusiasm about the book on Twitter, saying he was "excited to share this incredible #YearInSpace experience."