NASA’s Landmark Twins Study Reveals Resilience of Human Body in Space


Results from NASA’s landmark Twins Study, which took place from 2015-2016, were published Thursday in Science. The integrated paper — encompassing work from 10 research teams — reveals some interesting, surprising and reassuring data about how one human body adapted to — and recovered from — the extreme environment of space.

The Twins Study provides the first integrated biomolecular view into how the human body responds to the spaceflight environment, and serves as a genomic stepping stone to better understand how to maintain crew health during human expeditions to the Moon and Mars.

Retired NASA astronauts Scott Kelly and his identical twin brother Mark, participated in the investigation, conducted by NASA’s Human Research Program. Mark provided a baseline for observation on Earth, and Scott provided a comparable test case during the 340 days he spent in space aboard the International Space Station for Expeditions 43, 44, 45 and 46. Scott Kelly became the first American astronaut to spend nearly a year in space.

“The Twins Study has been an important step toward understanding epigenetics and gene expression in human spaceflight,” said J.D. Polk, chief Health and Medical Officer at NASA Headquarters. “Thanks to the twin brothers and a cadre of investigators who worked tirelessly together, the valuable data gathered from the Twins Study has helped inform the need for personalized medicine and its role in keeping astronauts healthy during deep space exploration, as NASA goes forward to the Moon and journeys onward to Mars.”

Living and working in space requires human perseverance. Future missions will focus on exploration at greater distances from Earth; to the Moon and then to Mars. These missions will mean humans will stay in space for extended durations. To ensure that these goals are achieved, NASA’s astronauts must be able to perform at peak productivity under even the most daunting conditions. Credits: NASA

Key results from the NASA Twins Study include findings related to gene expression changes, immune system response, and telomere dynamics. Other changes noted in the integrated paper include broken chromosomes rearranging themselves in chromosomal inversions, and a change in cognitive function. Many of the findings are consistent with data collected in previous studies, and other research in progress.

The telomeres in Scott’s white blood cells, which are biomarkers of aging at the end of chromosomes, were unexpectedly longer in space then shorter after his return to Earth with average telomere length returning to normal six months later. In contrast, his brother’s telomeres remained stable throughout the entire period. Because telomeres are important for cellular genomic stability, additional studies on telomere dynamics are planned for future one-year missions to see whether results are repeatable for long-duration missions.

A second key finding is that Scott’s immune system responded appropriately in space. For example, the flu vaccine administered in space worked exactly as it does on Earth. A fully functioning immune system during long-duration space missions is critical to protecting astronaut health from opportunistic microbes in the spacecraft environment.

A third significant finding is the variability in gene expression, which reflects how a body reacts to its environment and will help inform how gene expression is related to health risks associated with spaceflight. While in space, researchers observed changes in the expression of Scott’s genes, with the majority returning to normal after six months on Earth. However, a small percentage of genes related to the immune system and DNA repair did not return to baseline after his return to Earth. Further, the results identified key genes to target for use in monitoring the health of future astronauts and potentially developing personalized countermeasures.

“A number of physiological and cellular changes take place during spaceflight,” said Jennifer Fogarty, chief scientist of the Human Research Program at NASA’s Johnson Space Center in Houston. “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.”

Part of the record-setting one-year mission, the NASA Twins Study incorporated 10 investigations to advance NASA’s mission and benefit all of humanity. Scott participated in a number of biomedical studies, including research into how the human body adjusts to known hazards, such as weightlessness and space radiation. Meanwhile, Mark participated in parallel studies on Earth to help scientists compare the effects of space on a body down to the cellular level. The findings represent 27 months of data collection.

The Twins Study helped establish a framework of collaborative research that serves as a model for future biomedical research. Principal investigators at NASA and at research universities across the nation initiated an unprecedented sharing of data and discovery. Supported by 84 researchers at 12 locations across eight states, the data from this complex study was channeled into one inclusive study, providing the most comprehensive and integrated molecular view to date of how a human responds to the spaceflight environment. While significant, it is difficult to draw conclusions for all humans or future astronauts from a single test subject in the spaceflight environment.

“To our knowledge, this team of teams has conducted a study unprecedented in its scope across levels of human biology: from molecular analyses of human cells and the microbiome to human physiology to cognition,” said Craig Kundrot, director, Space Life and Physical Sciences Research and Application Division at NASA Headquarters. “This paper is the first report of this highly integrated study that began five years ago when the investigators first gathered. We look forward to the publication of additional analyses and follow-up studies with future crew members as we continue to improve our ability to live and work in space and venture forward to the Moon and on to Mars.”

The unique aspects of the Twins Study created the opportunity for innovative genomics research, propelling NASA into an area of space travel research involving a field of study known as “omics,” which integrates multiple biological disciplines. Long-term effects of research, such as the ongoing telomeres investigation, will continue to be studied.

NASA has a rigorous training process to prepare astronauts for their missions, including a thoroughly planned lifestyle and work regime while in space, and an excellent rehabilitation and reconditioning program when they return to Earth. Thanks to these measures and the astronauts who tenaciously accomplish them, the human body remains robust and resilient even after spending a year in space.

For more information about the NASA Twins Study, visit:


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April 15, 2019 10:21 pm

Good article. A bit wordy, but otherwise good.

Joel O’Bryan
April 15, 2019 10:28 pm

The problem with most telomere studies is the fact telomere lengths are measured in a heterogenous population of cells. White blood cells encompass many different types of immune function cells each with very different replication backgrounds and turn-over kinetics. TCells or B Cells or entire lymphocytes, or even more broadly simply all White blood cells. Even focusing on say just one like TCells, within that group are broadly two groups, naive and memory expanded clones.
Each group and subdivisions have different replication patterns and turnover kinetics.
The effect being that average telomere length shifts can be real changes in telomerelength in clonal populations, or they can simply reflect weighted population shifts of sub-groups with different average lengths of clones changing the overall average telomere length readout. Without some more sophisticated sampling or single cell sorting (rarely done) it is impossible to determine which (or both) effect caused the average telomere length to shift up or down.
Traveling right now. But when I get home to my work computer I’ll get the science paper and see what their methods were.

April 15, 2019 11:08 pm


Lance Wallace
April 15, 2019 11:54 pm

The astronaut seems to have gotten smarter in space–both speed and accuracy on the cognition tests improved. Then he came back to Earth and immediately dropped below his baseline before returning to it later. A clear indication that gravity makes us dumber.

Ron Long
April 16, 2019 3:20 am

Now that’s what I would call a real Separated Twins Study! Remember from a few days ago a sequence of comments and replys in the Moonbat article there was a long exchange about separated twins. My identical twin brother and I at times deal with an illness/physical mis-adventure/stress episode and appear to age faster, but overall seem to come to some baseline where we end up looking identical again.

April 16, 2019 4:09 am

If this research leads to advances in general medicine it will be a welcome bonus.

I am thinking of the immune system. Rheumatoid arthritis is a devastatingly debilitating condition caused by total failure of the immune system such that, in effect, it attacks itself. There is no current cure nor meaningful treatment.

Good research and precis.

April 16, 2019 4:25 am

“However, a small percentage of genes related to the immune system and DNA repair did not return to baseline after his return to Earth.”

Significant or insignificant? I assume this will be followed to see if it returns to baseline or if this change results perhaps in the development of some form of cancer?

Tom Abbott
April 16, 2019 4:59 am

“While in space, researchers observed changes in the expression of Scott’s genes, with the majority returning to normal after six months on Earth. However, a small percentage of genes related to the immune system and DNA repair did not return to baseline after his return to Earth.”

I am very much in favor of these types of studies because humans will spend some time in weightlessness during the initial stages of humans moving into the Earth/Moon space, but the long-term human future in space will be living in a one-Earth-gravity environment safe from radiation.

If humans don’t have some kind of rudimentary 1G environment in space in the next 25 years, I would be surprised.

All it would require is to take two habitation modules, one placed at each end of a mile-long cable, which when put in motion around the center at one revolution per minute would generate one Earth-equivalent gravity within each module. My formula for this is: 1 (mile in diameter)+ 1 (rpm) = 1 (Earth-equivalent “gravity”).

Cover these modules with a one-meter-thick coating of water ice to provide radiation protection for the humans inside.

The International Space Station is supposed to be retired in the coming years. Some industrious billionaire should offer to take a few of those space station modules off their hands and repurpose them into a rotating, one-Earth-gravity demonstration project.

They could take a few other of those space station modules and turn them into rotating Aldrin cyclers that travel in orbits that come close to both the Earth and Mars and can be used to transport people to and from the Earth and Mars. As the craft swings by the Earth, you hop on, travel to Mars, and hop off as it swings near Mars.

The International Space Station has quite a few modules up there. They probably still have a little life left in them, plus, and a big plus, they are already in orbit. 🙂

Of course, some enterprising billionaire should have bought the Space Shuttle Launch System when NASA threw it away, if they really wanted to get into space in a big way. They could have bought it cheap. But no takers. Maybe there won’t be any takers for used space station modules, either.

Anyway, something will be rotating up there one of these days. It’s the future.

Alan in Kansas
Reply to  Tom Abbott
April 17, 2019 6:18 pm

The idea of simulating earth gravity by rotating the space craft is an old science fiction idea. Basically you replace gravity with centripetal force. However, as I remember from high school science class, there would be an additional force involved, the “coriolis effect”.

The coriolis effect is a perpendicular force acting on a mass moving within a rotating field. This counterforce might play havoc with all the fluid movements within the body and its cells.

On earth the human body is minuscule in comparison to the size of the earth-rotation system. So the coriolis effect is not significant. But in a small local rotating system (“mile-long cable”) the size ratio to the human body might create a stronger counterforce.

Gravity remains a very elusive force, and the human body has evolved over eons under earth gravitation. I am pessimistic about the human biological system ever being able to adapt to long space flights and low gravity systems.

Reply to  Alan in Kansas
April 17, 2019 9:30 pm

My guess is that if the challenge is solved it will be with something less than 1 g. A lot of problems (especially structural problems, but also Coriolis forces) shrink if you don’t need a full 1 g.

I’m no expert, but it is my understanding that long term survival outside the Van Allen radiation belt would require shielding, which would necessarily be quite massive. Even if the problem of lifting or finding enough mass for that purpose is solved, spinning the heavy structure fast enough to achieve 1 g would require dauntingly beefy construction.

If you can get by with less centrifugal “gravity” then a lot of those problems get easier — and the answer might tell us whether long-term habitation is even possible in some interesting places.

Would ½ g be sufficient? How about 0.38 g (= Mars gravity)? How about 0.165 g (= Moon gravity)? How about 0.14 g (= Titan & Ganymede gravity)?

Before a long term space mission using centrifugal “gravity” is even planned, it would be necessary to learn just how little gravity the human body can get away with. That knowledge will be expensive, unfortunately.

April 16, 2019 5:52 am

Written by: Fluffy the Rabbit.

Concept Design: Fluffy the Rabbit.

Artistic License and smoke machine: Fluffy the Rabbit.

Although; cutting edge, landmark, cross-disciplinary, and monumental, Egg Hunter’s are still wondering if the chicken came before the egg. Grant our enterprising researchers just a few million more and we should know.

Reply to  RobR
April 16, 2019 7:04 am

You left out important, valuable, collaborative, comprehensive, unique, innovative, tireless, unprecedented (2x), and, most of all, integrated (7x). It was really integrated.

Reply to  Dave Burton
April 16, 2019 7:17 am


April 16, 2019 3:16 pm

How about all the non twin studies.
Like after 6 months about half had permeant sight damage.
How did he miss the bullet on muscle atrophy, particularly his heart.
I wonder how he missed all the extra gamma living outside our atmosphere.
His brother is married to Representative Gabrielle Giffords, shot
with a 9mm just above the left eye that exited out the back of her head.
Google ballistic 9mm geltest.
I have a brother that has a head injury, and every time she comes out with her phony speech impediment to band guns, my blood pressure goes up.
Go to Mars..
Just wear lead underwear, bring your own atmosphere and gravity.
Oh for got the water.

Want to lead about space travel.
Google George Carlin and MAD TV , Apollo Moon hoax.
In the 60s and 70s we guided rockets with
accelerometers. I know I test 100s of them. Gravity is different so you had to put in your location in to the test.
They don’t work with out gravity, period. So how did they know were they were and how fast they were going.
Simple, radars on earth, would then uplink the data that IBM computers calculated for them.
Radar that that can track a 12 ft object 237,000 miles away.
They must of had some magic resolvers on the sweep sensors of the radar.
Best part as the world turns you just use the next radar.
It took them 63 hours to get there. They left orbit at 25,000 or 27,000 mph depending how is talking for NASA.
Why not 9 hours.
Gravity slows them down till they were only going 2000 mph.

About 85% of the way there, then the moons gravity takes over.
Ok I buy it.
Then how could you be weightless once you left orbit.

Reply to  tom
April 16, 2019 5:22 pm

You’re 15 days late, Tommy.
How’s your cat?

Mark - Helsinki
April 17, 2019 8:14 am

Rofl, space destroys the human body, it’s merely a matter of time and there is a max time you can spend in mere lower orbit. Go a bit further out and the max time shrinks dramatically.

None of us will be a live by the time they even seriously think about sending people to Mars and even then, it;s a certain death sentence, possibly a very slow death sentence.

Reply to  Mark - Helsinki
April 17, 2019 8:34 am

Send public school teachers first.

my boat shot a missile in 71 at the cape.
There were 6 of us that were in the Missile Control Center.
i was a senior guy at the time.
One day off and at the early mornin g roll out of Apollo 16 we bummed into a suit.
He ended up giving us a 9 hour tour of the Cape.
i was at the top of the vertical assembly on a cat walk 550 ft looking down on Saturn 5 rockets.
He turned out to be one of two men that were just under the director.
He had been the Weapons officer on the George Washington.
It was great.
but why take the day off to be with us.
We were big time Rocket guys, understood all this stuff and had a million questions.
I think most of his day was to smoosh VIPs to keep the money rolling in.

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