Twin studies are the closest scientists can get to putting a person in two places at once. But they are also hard to come by: Identical twins are relatively rare (just three to four per thousand births worldwide). Even rarer are identical twin pairs that are astronauts. In fact, right now, just one set exists: Scott and Mark Kelly.
Over the past few years, the brothers have participated in what’s now called the NASA Twin Study: A first-of-its kind longitudinal study in which one brother (Scott) spent a year onboard the International Space Station (ISS) and the other (Mark, who had already retired from spaceflight) spent those same 12 months on Earth. That year, and in the ones that followed, the pair provided blood, urine, and stool samples—in addition to undergoing a slew of physiological and medical tests—to help researchers understand how the human body responds to life in space. The most recent results were published this week in the journal Science.
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The researchers, echoing what NASA has suggested previously, said the twins study turned up no showstoppers - no shocking health consequences that would But Scott Kelly says he' s actually a few milliseconds younger still, due to having spent 500 more days in space than his astronaut brother.
NASA liked the idea and put out a call for outside researchers to submit proposals to study Oddly, NASA reported that Kelly’ s telomeres grew while he was in space . This is another claim They could be due to living in microgravity, a lack of exercise or disturbed sleep, or a diet of freeze-dried foods.
A major roadblock to understanding how space affects the human body is that it’s incredibly difficult to blame any changes that occur on spaceflight alone. For example, a slight mutation in an astronaut’s DNA could have been from time spent in zero gravity or excess radiation, or it could be from any number of environmental conditions that would also have affected them on Earth. But if that specific change is seen in one twin who spent a year in space (340 days, to be exact) and no comparable change happened in the twin who spent the same year on Earth, researchers can say with a bit more confidence that space had something to do with it. This is still far from a perfect way of pinpointing space-related bodily changes, because a study with just two people in it is awfully small. But it’s better than comparing an astronaut to the average Earthling.
The ultimate question is how the human body will hold up during long term space travel. NASA has tentative plans for missions to Mars and trips back to the moon, which would mean more time in space than quick jaunts to the ISS have prepared us for. Knowing if our bodies can stand the strain is crucial.
What space does to the human body
Nasa’s landmark Twins Study reveals physical ‘resilience’ of astronauts
That’s the extremely topline summary of NASA ’ s “ Twins Study The study tracked the physiological and cognitive changes of astronaut Scott Kelly as he spent And in another genetic surprise, the ends of Scott’s chromosomes ― a protective sequence called telomeres ― actually lengthened in space .
Dubbed the Twins Study , it hinged on the results of Kelly’s tests being compared with those of his identical twin , retired astronaut Mark Kelly, who remained on Earth NASA ’ s goal was to gain insight into the hazards that astronauts could face on proposed long-term missions to the Moon and Mars.
So what does a year in space actually do to the body? Overall, the results of the twin study suggest that for a year’s time, “human health can be mostly sustained over this duration of spaceflight.” Many changes were temporary and slowly stalled upon Kelly’s return to Earth, while others have stuck around. Understanding all of these changes will take time, but here’s what we know for now.
Length of telomeres:
Telomeres are molecules that sit at the end of DNA segments and protect them from damage and degradation. Aging, as well as other factors like stress and environmental changes, can speed this process up. Some researchers speculated that the stressor of space would cause Kelly’s telomeres to deteriorate. However, the opposite turned out to be true: They lengthened. Researchers saw an increase in the activity of the proteins that regulate telomere length—higher than both before he left for space and upon his return.
Why that is is not entirely clear. Researchers know that following a healthy diet and exercise regimen—which Kelly did while on board the ISS—could have this effect on the telomeres. Astronauts stick to strict nutritional plans and workout routines to fight back against the muscle and bone atrophy of space, so some of them might actually have healthier lifestyles while afloat than they do on the ground. It’s also possible that the drastic shift in environmental conditions caused his body to produce new cells, with longer telomeres, as a protective mechanism.
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Living in space is not the same as living on Earth. Many things are different. Our bodies change in space . The way we stay clean and neat is different too. In space , astronauts' bodies change. On Earth, our lower body and legs carry our weight. This helps keep our bones and muscles strong.
Get the latest updates on NASA missions, watch NASA TV live , and learn about our quest to reveal the unknown and benefit all humankind. The Twins Study was the first study of its kind to compare molecular profiles of identical twin astronauts with one in space and another on Earth.
Gene activity changed:
The activity of our genes—which results in permanent alterations to our DNA—change all the time. When this happens some proteins become more active and some less. It’s part of the aging process, and universal to humans. Certain gene changes can lead to disease while others can lead to an increase in fitness or cardiovascular health. But gene activity can also change when people are exposed to radiation, which space travel has a ton of due to its lack of protection from Earth. Scott Kelly saw an increase in activity in many genes that remained inactive in his brother Mark.
While scientists don’t know for sure, they surmise that this shift in activity is at least partially related to the amount of radiation exposure Scott Kelly received compared to his brother. An increase in radiation exposure may cause cells to attempt to repair themselves, thereby increasing certain gene activity.
Other genetic changes, like DNA mutations, were also present in Scott Kelly that didn’t exist in his brother. While those changes aren’t immediately concerning, their activity over time could increase the chances of cancer. This could be far more concerning when people spend longer than a year in space, as these mutations accumulate.
Altered body bacteria:
The microbes that live in and on our bodies—what scientists call the microbiome—can have a significant effect on our health. They affect digestion, influence our metabolism, and can also play a role in our immune, bone, muscle, and brain health. To understand how our resident microbes survive in space, researchers took stool samples from Kelly before, during, and after his days in space and compared them to those of his twin.
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Humans evolved on Earth — everything about us expects the familiar tug of gravity, and the body can behave in unexpected ways when sent into space . Some of the changes were expected based on past studies on astronauts. Living in space causes muscles to shrink and bones to thin, and the
Nasa has found out the impact of space travel on the body by studying an astronaut and his NASA . Sometimes we all need some time apart from our siblings. But imagine if your brother popped NASA . Height: Scott came back 5cm taller than his twin ! This was because the ISS' s microgravity makes the
They found that while gut bacteria in particular did change drastically while he was in space, the microbiome quickly shifted back to more normal levels upon his return to Earth. He didn’t experience any major loss of any bacterial diversity—which scientists think is a crucial part of a healthy microbiome—during the process. And the fact that things shifted back to normal quickly once he came back home suggests that this gut upheaval wouldn’t have serious longterm effects. (For context, previous studies have shown that gut microbes can shift significantly after just a few weeks of eating a different diet or living in a different place.)
With all of this new information, the researchers write, they can begin to ask more specific, directed questions about how the body adapts to space—and begin to better answer whether or not it’s safe or wise for humans to travel to Mars. Researchers can also work on ways to combat these changes, either through novel drugs or other interventions, with the ultimate goal of making all spaceflight—no matter how long its duration—safer and less mysterious.