For more than 60 years, NASA  and other space agencies have sent some of humanity’s best  and brightest into space.

Not just doctors and PhD scientists, but also national cycling champions  and microgravity marathon runners. So thanks to all those  astronauts, we know what space does to a human body in peak physical condition.

But what about the rest of us? How does space affect someone whose  greatest endurance achievement is a lot closer to marathoning every episode of

Avatar: The Last Airbender in a weekend? Well, due to the enormous cost of space  travel and strict astronaut selection processes, researching that question has  been a non-starter … until very recently. In 2021, four civilians spent  three days in Earth’s orbit, crammed into a spacecraft  cabin the size of a cargo van. This was the Inspiration4  mission, and the research papers on what happened to its crew are  finally starting to trickle in.

So let’s see how space affected their bodies, and what this mission taught us  about the future of space travel. [♪ INTRO] As commercial space travel grows in  popularity, more civilians will go to space. And if you’re trying to study  the effects of human spaceflight, those extra bodies are a good  thing in more ways than one! Not only do they give us a view into  how a quote-unquote “average” body handles space travel, but they also increase the overall sample  size of space travelers.

And more data is always useful. And even if the profile of your  typical NASA astronaut doesn’t change anytime soon, civilian  missions do benefit NASA, too. Because before sending anyone to Mars, they still need to answer a lot of open  questions about long-term space travel.

Like, how will NASA monitor  those astronauts’ health? And what medical tests can  astronauts reliably conduct on each other so far away  from the rest of humanity? Researching those questions  is much easier with civilians than it is with professional astronauts,  because the pros are in short supply and take at least three or four years to train.

So the Inspiration4 mission gave  scientists like the ones at the Translational Research Institute  for Space Health, or TRISH, an opportunity to answer some of these questions. Each crewmember wore an Apple  Watch to passively record a variety of physiological metrics, like  their pulse, physical activity, and the amount of oxygen in their blood. They also had an iPad to take  surveys about their mood and complete cognitive tests like NASA astronauts  do on the International Space Station.

As for more science-y looking  equipment, the crew used portable, miniaturized ultrasound  machines…connected to a smartphone. This allowed them to collect scans  of each other’s eyes, bladders, and neck veins, and look for indicators  of common astronaut health problems. And finally, to see how  their immune systems fared, they had to collect blood  samples, skin swabs and more.

Some were like the ones you’d  get at an annual physical and others were a bit more niche. Now, all of these measurements  were also taken on Earth… both before the crew launched  and after they got back. And in these two cases, the astronauts  didn’t do all the poking and prodding.

Actual experts did it for them. By comparing the in-flight data  against the pre- and post-flight data, researchers could compensate for the  study’s incredibly small sample size of four whole people, and get results  that were at least a bit more rigorous. Now, science takes time.

So even though Inspiration4  happened way back in 2021, the first round of research  wasn’t published until 2024. So now we’re here to break  down some of the results. First, and most importantly, the four  civilian astronauts did not experience any serious health problems  during or after the mission.

This suggests short-term space travel does not pose a significant risk to everyday people. Which still does not make me want to go to space, but I’m happy for all of you who do. And in one case, there was  a pleasant surprise compared to the known effects of long-term missions.

Astronauts on multi-month trips  are prone to develop blood clots, but scans of the four astronauts’  jugular veins revealed no abnormalities in their blood flow. So at the very least, clots  may be less of a concern if you’re only going up there for a few days. The next result was a promising  update on scientists’ hunt to explain why a lot of astronauts get  motion sickness in space.

We’ve covered the topic in a previous episode, so you can check that out for more info. But in Inspiration4’s case,  scientists wanted to test if we can actually predict if an astronaut  will get space sick ahead of time. And one of the ways they did  that was by scanning their eyes.

Now, eyes might not be an absolutely necessary organ for a human to navigate the world. But they sure are handy. They help tell us how we’re oriented in space.

Here’s up and here’s down. And they help us know when we’re moving or if our orientation to our idea  of “up” and “down” have changed. But for many people, their  eyes aren’t symmetrical.

Specifically, how they’re aligned  when you’re looking at something. On Earth, this asymmetry doesn’t really matter. Our bodies have developed with  a clear sense of up and down thanks to the planet’s gravity.

But the microgravity environment of a  spaceship zooming around the planet, or off into the wild black yonder,  is a completely alien experience. So researchers have hypothesized  that when astronauts go to space, we lose that sense of up and down, and  the usual directional cues we get on Earth might not help our brains fix the problems. This might be the cause of space motion sickness.

And tests for Inspiration4  showed that two of the astronauts had a consistent change in the  way their eyes were aligned before and after the flight. These were the same two people  who didn't get motion sick when they were in space, which suggests that their ocular alignment shifted to  compensate for microgravity. So if more research continues  to show the same results, space agencies could start using this kind of eye scan to screen astronaut candidates.

If not to weed out people for certain missions, then at least to send them up with  our best anti-nausea medications. Motion sickness wasn’t the only thing that  Inspiration4 collected data for, though. The mission also showed that “everyday”  bodies experience a few well-known changes that happen to those of  professional astronauts as well.

For example, your telomeres… the  protective caps at the end of your chromosomes… they get longer in space  but rapidly shorten after you get back. This means space travel may make  your DNA more vulnerable to mutation. And then, there’s the rather disturbing  fact that space can reactivate viruses lying dormant in your body…like the  ones that cause mono and chicken pox.

Previous research had revealed that  the longer astronauts are in space, the more virus they shed, making them  more likely to infect their crewmates. And while astronauts’ infections  have generally been asymptomatic, a reactivated virus can be life-threatening. And that’s a problem for both  civilian and NASA astronauts, and we don’t have a solution for it yet.

So let’s move onto a result that  differs between the two populations: Inspiration4’s civilian astronauts  were slower and less accurate on the same cognitive tests that NASA  astronauts take while in space. Although, good news: they did  return to normal performance after they got back to Earth. Declines like these are typically seen  on the International Space Station when astronauts don’t get enough sleep, but the civilian astronauts  seemed to sleep plenty.

They actually slept longer than most do in space. So while the cause of these  cognitive declines is unclear, researchers speculate that they might  actually be happening to astronauts on the ISS, too … just  without us knowing about it. The first couple of days  on the ISS are jam-packed, and NASA typically doesn’t get  cognitive data until a few days later.

But on Inspiration4, the crew started  taking these tests right away, suggesting that these declines could be just a normal result of humans adapting to microgravity. And if that’s true, we would  expect to see civilian astronauts return to baseline after  four or five days in space. And finally, let’s end on what might be the most impactful result for future spaceflight: All of the measurements the  Inspiration4 crew took of each other, except those from the most technical eye exam, were totally usable by  researchers back on the ground.

And that’s in spite of the fact that  these civilian astronauts received no real-time guidance when testing each other. That is…and I can’t stress this enough…not at all how it works for the professionals. On the ISS, astronauts use traditional  devices you'd find in a doctor's office, not handheld, iPhone-controlled ultrasounds.

And professional astronauts  have a staff of experts on Earth guiding them through a  procedure every step of the way! But TRISH scientists had a  method to this research madness: When we send astronauts to Mars, there  will be up to a 23-minute time delay for communications each way. And that makes real-time  instructions completely impractical.

Astronauts on long-term space flight missions will need to take measurements on their own. So by testing whether a minimally-trained  civilian crew could collect usable data, using portable ultrasounds,  TRISH could shed light on how to monitor the health of  astronauts on long-term space missions, and what procedures will  require more in-depth training. Inspiration4 kickstarted a new  era of civilian space travel, and taught us that civilians are up  to the task of navigating the stars.

And on September 10th, 2024, the second all-civilian space mission launched: Polaris Dawn. One goal for that mission was to study  how space radiation affects human health. And to do that, the crew flew through  one of Earth’s radiation belts.

And two of them, including Jared  Isaacman who led both missions, became the first civilians to  go outside their spacecraft. All four astronauts returned  safely to Earth five days later, with loads more data for TRISH to dig into. And right now, there are two more  Polaris Program missions scheduled.

And with each one, we’ll get that much closer to answering the big questions about  how space affects everyday people. Like how much I have to worry  about getting chicken pox again, and infecting my crewmates. Although if I was stuck in quarantine up there, I could pass the time by marathoning Avatar again.

Support for this episode was contributed  by the Translational Research Institute for Space Health at Baylor College of Medicine. TRISH is an applied health research  catalyst that funds high-impact scientific studies and  technologies to keep astronauts healthy during deep space exploration. TRISH is empowered by the  NASA Human Research Program, and a consortium led by Baylor College of  Medicine with partners MIT and Caltech. [♪ OUTRO]