Skip to main content

NASA’s twin study reveals effects of time spent in space on the human body

Scott Kelly at work on ISS maintenance with the station’s solar arrays visible in the background. NASA

What exactly happens to a human body in space? Despite decades of astronauts going on space missions, this question remains hard to answer. The problem is that there is a great deal of individual variation between humans, so everyone’s body is different. This makes it hard to compare the physiological effects of space travel between astronauts and those of us who stay on Earth.

But now a new NASA study has revealed clues about the effects of space by studying a pair of twins. Two retired astronauts, twin brothers Scott and Mark Kelly, lent their bodies to science to be studied for a period between 2015 and 2016. During this time, Mark stayed on Earth while Scott spent 340 days aboard the International Space Station (ISS). Scientists were able to compare how their two bodies responded over that time, without confounding factors of genetics and large individual differences.

The NASA researchers studied factors like gene expression changes, immune systems responses, and cognitive functioning. One significant finding was that spending time in space seems to effect aging. Scott had changes to his DNA, showing longer telomeres — the caps at the end of a DNA strand. When compared to his brother’s teleomeres, Scott’s telomeres were longer while he was in space and then shorter after his return to Earth, eventually returning to normal after six months.

Another finding was the way in which Scott’s genes expressed. Gene expression is part of the way that genes interact with an environment, and it was found that Scott’s genes expressed differently in space. His genes mostly returned to normal after he returned to Earth, but a few genes seemed to be permanently altered by time spent in space. The effected genes included those related to the functioning of the immune system and DNA repair.

“A number of physiological and cellular changes take place during spaceflight,” Jennifer Fogarty, chief scientist of the Human Research Program at NASA’s Johnson Space Center in Houston, said in a statement. “We have only scratched the surface of knowledge about the body in space. The Twins Study gave us the first integrated molecular view into genetic changes, and demonstrated how a human body adapts and remains robust and resilient even after spending nearly a year aboard the International Space Station. The data captured from integrated investigations like the NASA Twins Study will be explored for years to come.”

Full results of the study are published in the journal Science.

Editors' Recommendations

Georgina Torbet
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
Roman Space Telescope will survey the sky 1,000 times faster than Hubble
NASA’s Nancy Grace Roman Space Telescope

Since its launch in 2021, the James Webb Space Telescope has been delighting space fans with its stunning views of space objects near and far. But NASA has another space telescope in the works that will be able to help answer even more of the big questions in astronomy. The Nancy Grace Roman Space Telescope, set to launch in 2027 and colloquially known as Roman, will look at vast areas of space to help cosmologists understand the universe on a large scale.

In astronomy research, it's important to be able to look both in very great detail and on a very wide scale. Telescopes like Hubble and James Webb have exceptional sensitivity, so they can look at extremely distant objects. Roman will be different, aiming to get a broad view of the sky. The image below illustrates the differences between the telescopes, showing what Roman and Hubble can capture in one go and comparing Hubble's detailed, but narrow view to Roman's much wider view.

Read more
NASA and SpaceX target new Crew-6 launch date after scrubbed effort
Crew-6 astronauts aboard a SpaceX Crew Dragon capsule.

After NASA and SpaceX scrubbed the launch of Crew-6 just a couple of minutes before lift-off early on Monday morning, officials have announced they're now targeting Thursday for the next launch effort.

The team called off Monday’s launch attempt at the Kennedy Space Center in Florida when it suddenly encountered an issue in the ground systems affecting the loading of the ignition fluids for the Falcon 9 rocket that will carry the astronauts to the International Space Station (ISS) inside the Crew Dragon Endeavour capsule.

Read more
NASA and SpaceX Crew-6 mission ready for launch tonight
From left, NASA astronauts Warren “Woody” Hoburg and Stephen Bowen, along with Roscosmos cosmonaut Andrey Fedyaev and UAE (United Arab Emirates) astronaut Sultan Alneyadi, prepare to depart the Neil A. Armstrong Operations and Checkout Building at Kennedy Space Center in Florida during a dress rehearsal for NASA’s SpaceX Crew-6 mission launch on Thursday, Feb. 23, 2023.

NASA and SpaceX are ready to launch four astronauts to the International Space Station, with preparations underway and launch scheduled for late tonight PT. The Crew-6 mission is set to launch at 1:45 a.m. ET on Monday, February 27 (10:45 p.m. PT on Sunday, February 26) from Launch Complex 39A (LC-39A) at the Kennedy Space Center in Florida using a SpaceX Cargo Dragon and Falcon 9 rocket.

In a press conference following a readiness review on Saturday, February 25, NASA officials said that the crew and hardware had been given the go-ahead. "We had a good launch readiness review and we're on track for the 27 launch," said Dana Weigel, deputy manager of the International Space Station Program at NASA’s Johnson Space Center in Houston. "This morning I had a chance to talk to the crew. They're doing great. Spirits are high and they are ready to go."

Read more