NASA study highlights profound effects of space travel on human body

PHOTO: Former Astronaut Mark Kelly and his brother, Astronaut Scott Kelly, speak to news media outlets about Scott Kellys one-year mission aboard the International Space Station, Jan. 19, 2015.PlayRobert Markowitz/NASA, FILE
WATCH NASA reveals findings on study of space's effect on the body

NASA released the results of a momentous twin study on Thursday, which found that space travel has profound effects on the human body. The findings could shape NASA’s 2020 mission to Mars — a journey that would take astronauts at least three years.

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Astronaut Scott Kelly was separated from his astronaut twin brother Mark Kelly on March 27, 2015. Scott Kelly lived on the International Space Station — while his brother lived on Earth — and returned on March 1, 2016. Three years later, the results of the study, announced from NASA’s Houston headquarters, showed that long-term space missions are likely to cause major changes to astronauts’ metabolisms, genetics and cognitive performance. What’s more, the changes could last months after astronauts return to Earth, if not longer.

PHOTO: Former Astronaut Mark Kelly and his brother, Astronaut Scott Kelly, speak to news media outlets about Scott Kellys one-year mission aboard the International Space Station, Jan. 19, 2015. Robert Markowitz/NASA, FILE
Former Astronaut Mark Kelly and his brother, Astronaut Scott Kelly, speak to news media outlets about Scott Kelly's one-year mission aboard the International Space Station, Jan. 19, 2015.

Space presents unique stresses to the human body. With lower gravity levels, for example, bones and muscles are more likely to become weak since they no longer have to support the weight of the body. Space flight also affects astronauts’ eyes, causing what’s now called space flight-associated neuro-ocular syndrome, characterized by swelling in the optic nerve head, among other symptoms.

PHOTO: Scott Kelly is seen inside the Cupola, a special module which provides a 360-degree viewing of the Earth and the International Space Station, July 12, 2015. NASA via Getty Images
Scott Kelly is seen inside the Cupola, a special module which provides a 360-degree viewing of the Earth and the International Space Station, July 12, 2015.

Astronauts in space are also exposed to higher levels of radiation without the Earth’s atmosphere there to act as a filter. Dr. Christopher Mason, study investigator and associate professor of physiology and biophysics at Weill Cornell School of Medicine, told ABC News that radiation levels "are about eight times higher" on Mars than they are on Earth.

Until this study, the majority of astronaut research had only looked at space missions lasting six months or less. Writing for The Sydney Morning Herald in 2017, Scott Kelly said that by the end of his mission, he had spent a career total of 520 days in space, "more than any other NASA astronaut.”

During a news conference on Thursday, Scott Kelly said he was ready to go back to space again. "Put me in coach," he said. "I'm ready."

PHOTO: Commander Scott Kelly of NASA rests in a chair outside of the Soyuz spacecraft minutes after he and two Russian cosmonauts landed in a remote area on March 2, 2016 near the town of Zhezkazgan, Kazakhstan. Bill Ingalls/NASA/Getty Images, FILE
Commander Scott Kelly of NASA rests in a chair outside of the Soyuz spacecraft minutes after he and two Russian cosmonauts landed in a remote area on March 2, 2016 near the town of Zhezkazgan, Kazakhstan.

Since the Kelly brothers are genetically identical, researchers were able to control for genetic differences in their study, so that “the only changes that [we] would see would be because of environmental changes,” senior author Brinda Rana, PhD, professor of psychiatry at the UC San Diego School of Medicine told ABC News.

“The study provided insight into the body’s response to space flight…[and] captured an integrated view on the molecular, behavioral and physiological changes experienced by a middle-aged man on Earth over a two-year period,” Rana said in a press release.

By the end of the mission, Scott Kelly had clear signs of DNA damage, dehydration, and cognitive decline, the researchers found. Many of his telomeres — stretches of DNA that protect our genetic data and have been associated with a person’s lifespan — were also shorter.

PHOTO: In this undated photo provided by NASA on March 1, 2016, astronaut Scott Kelly looks out the cupola of the International Space Station. NASA/AP Photo
In this undated photo provided by NASA on March 1, 2016, astronaut Scott Kelly looks out the cupola of the International Space Station.

“This may represent the way the body compensates to counteract some of the effects of space,” Rana said, noting that the DNA damage was due to the radiation Scott Kelly was exposed to in space.

Several months after his return to Earth, Scott Kelly continued to exhibit these effects of space on his body. Although it’s unclear how permanent these effects are — or if they’re even totally related to his time in space — the study has prompted NASA to dig deeper. As the organization prepares for the mission to Mars, Rana said that “NASA has expanded [this] study to a larger group of astronauts, and is planning to send up another group.”

Navjot Kaur Sobti is an internal medicine physician at Dartmouth Hitchcock Medical Center/Dartmouth School of Medicine and a member of the ABC News Medical Unit.