Here’s How Much Spaceflight Changes the Body’s Biology in Just Three Days

Hayley Arceneaux is hardly the picture of a traditional astronaut. The 32-year-old physician assistant has a metal rod inserted into her leg to replace cancerous bone segments removed in a brawl with the disease as a child.

But in September 2021, she became the youngest American civilian to orbit the Earth as a member of SpaceX’s Inspiration4 mission. Led by billionaire entrepreneur Jared Isaacman, the trip was the first to carry an all-civilian crew of four people to space and opened a unique opportunity to investigate how spaceflight changes our bodies and minds—not for trained astronauts, but for everyday people. The crew agreed to have biological samples taken before, during, and after the three-day flight. They also tested their cognition throughout the trip.

In over 40 studies released last week, researchers found that radiation and low gravity rapidly changed the body’s inner workings. After just three days, the immune system and gene expression were out of whack, and cloudy thinking set in.

The good news? Upon returning to Earth, most of these troubles eased.

Together, the package of data is the largest to date detailing spaceflight’s impact on the body. “This is the beginning of precision medicine for spaceflight,” Christopher Mason at Weill Cornell Medicine, who co-authored some of the papers, told Nature. “This is the biggest release of biomedical data from astronauts,” he added when speaking to Science.

All the data acquired from the crew during and after their mission is publicly available in NASA’s Open Science Data Repository

Space Tourism

We’re in a new space race, with multiple countries sprinting to revisit the moon and beyond. At the same time, commercial spaceflight for those eager to see Earth-rise and experience the mind-boggling effects of zero gravity is becoming more common.

From NASA studies, we already know spaceflight changes the body. For the past six decades, NASA has carefully characterized impacts such as increased long-term cancer risks from radiation exposure, changes in vision, and muscle and bone wasting. Comparative data from twin astronauts Scott and Mark Kelly—with one twin on Earth and the other in orbit—found more specific biological changes relating to spaceflight.

However, most studies follow highly-trained astronauts. They often have a military background and are in tip-top physical shape. Their missions can last months in zero-gravity—obviously far longer than a three-day jaunt.

To make spaceflight available to the rest of us, analyzing biological changes in civilian astronauts could better represent how our bodies react to space. Enter Inspiration4. The lead sponsor, Isaacman, recruited three everyday people to go on the first commercial trip to orbit the Earth. Arceneaux and Isaacman were  joined by Sian Proctor, a lecturer who teaches geoscience, and an engineer, Christopher Sembroski. Their ages ranged from 29 to 51 years old.

The crew agreed to take blood, saliva, urine, and feces samples during their three days in space. They also wore fitness trackers and took cognitive tests. All this information was processed and added to the Space Omics and Medical Atlas (SOMA). The database includes the volunteer’s genomes, gene expression, and an atlas of proteins that make up and control bodily functions.

Inspiration4 orbited Earth at a much higher altitude than the International Space Station, where astronauts usually reside, so the new dataset captured biological changes on short-term, high-altitude missions with samples from a wider range of demographics. Up to 40 percent of the findings are new, Mason told Science

Surprisingly, the samples reflected bodily changes that have previously only been seen on long-term spaceflights. The most prominent was an increase in telomere length—the “protective” end caps that keeps our genetic code intact. When cells replicate, these protective caps erode—a biological signature that’s often associated with aging. 

However, during Kelly’s year in space, his telomeres actually grew longer, suggesting that in a way his cells were made biologically younger—not necessary a win, as abnormally long telomeres have been linked to cancer risk. Once he returned to Earth, however, his telomeres returned to their normal length.

Like Kelly, the Inspiration4 crew also experienced a sudden lengthening and shortening of their telomeres, despite only three days in space, suggesting fast-acting biological changes. Digging deeper, one research team found that RNA—the “messenger” molecule that helps translate DNA into proteins—was rapidly altered in the crew, similar to changes observed in people climbing Mount Everest—another extreme scenario where there is gravity, but limited oxygen and increased radiation.

To study author Susan Bailey at Colorado State University, the cause of telomere lengthening may not be weightlessness per se; rather, it’s likely due to radiation at high altitudes and in space. 

Another study found that space stressed the crew’s immune system at the gene expression level in a group of white blood cells—those that tackle infections and cancers. Some parts of the immune system seemed to be on high alert; but the stress of spaceflight also affected genes that battle infections, suggesting a decreased ability to fight off viruses and pathogens. Using multi-omics data, the team found a “spaceflight signature” of gene expression related to immune system function. 

The crew  also showed signs of cosmic kidney disease. Molecular signals highlighted a potential increased risk for kidney stones. While not a problem for a three-day flight, for a longer mission—say, to the moon or Mars—kidney problems could rapidly escalate into a medical crisis. 

The civilian astronauts’ cognition also faltered. Using iPads, the crew tackled a slew of mental tasks. These included, for example, the ability to focus and maintain attention in several standardized tests or to press a button when a stopwatch suddenly popped onto a screen. Within three days, their performance declined compared to when they were on the ground. 

“Our speed response was slower…that surprised me,” Arceneaux told the New York Times. However, rather than reflecting cognitive problems due to space travel, it could also be because the crew were distracted by the sight of Earth right out the window.

A Spaceflight Library

With data from just four people, it’s hard to draw conclusions. Most tissue samples were compared to previous data from NASA astronauts or the Japan Aerospace Exploration Agency. That said, when you see the same protein or genetic signatures changing across different missions and people, “that’s when you start believing it,” co-author Afshin Beheshti at the Blue Marble Space Institute of Science told Nature

All the data was gathered into the SOMA database for other scientists to explore, and tissue samples were stored in a biobank. As commercial spaceflights become more common, scientists may have the opportunity to collect data before, during, and after a mission to further grasp what traveling beyond Earth means for the rest of us. For example, are there any triggers for severe motion sickness while being shot into space?

These insights could also give us time to develop potential treatments to ward off the negative effects of spaceflight for longer trips across the solar system. 

Inspiration4 was just the first commercial sprint into space. Several other missions are on the books, including Polaris Dawn, which is set to launch as early as next month—with the goal of attempting the first commercial spacewalk. 

“Soon we’ll have more data from multiple missions and multiple crews. I’m optimistic about the future,” said study author Mason. 

As for Arceneaux, since landing back on Earth she’s continued her work as a physician assistant at St. Jude Children’s Research Hospital. Remembering her view from orbit, she told The New York Times, “We are all one on this beautiful planet.”

Image Credit: Inspiration4 crew in orbit / Inspiration4

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