Microgravity, or very weak gravity, on the International Space Station (ISS) is what lets astronauts glide and somersault around effortlessly as they orbit Earth. It is also a useful environment for gaining insights into human health, both in terms of the impacts of long-duration spaceflight and new perspectives on diseases that afflict people on our planet.

Space-based biomedical research was one of the key topics discussed last week at the ISS R&D Conference in Atlanta. Researchers highlighted some of the current work on the Space Station, as well as further studies NASA and the ISS National Laboratory hope to do while seeking to commercialize low-Earth orbit. They also aim to use the ISS as a stepping-stone to landing back on the Moon and eventually Mars.

As a physician certified in both internal and aerospace medicine, astronaut Serena Auñón-Chancellor has a keen interest in this work. She helped conduct several biomedical experiments as a flight engineer onboard the ISS for 197 days during Expeditions 56 and 57 in 2018, an experience she described to the audience at the conference. Scientific American sat down with Auñón-Chancellor to discuss the research she conducted and her own experiences with the impacts microgravity has on the human body.

[An edited transcript of the interview follows.]

What effects of microgravity did you experience?

The experience is personal for everybody. This was my first flight. I’d learned for years about all the different things that happen to the body, but you don’t know, until you get up there, how you’re going to feel. So when I got up there—certainly, your stomach doesn’t feel great, the first few days. You just don’t feel like eating as much. You feel like everything’s floating inside. Turning your head quickly in one direction and then the other, there was a bit of a lag [for the brain to catch up]. But that diminishes so quickly that after about the first week, you start thinking, “Okay, I’m beginning to feel like I’m normal again.”

We all see changes in the immune system. We see what they call latent viral reactivation [when dormant viruses begin reproducing], and that’s measured in our saliva. We have almost everything sampled and tested up there, from feces to saliva to urine to blood. But it’s interesting how quickly things do revert almost back to normal once you get down to Earth.

What are some of the key questions about how microgravity impacts human health?

I think the biggest health challenges—certainly for exploration-class missions, longer and longer missions—number one is radiation. We’re pretty well protected on the ISS—the thick shielding of the vehicle, Earth’s magnetic field and the atmosphere all provide protection. Once you change that baseline standard—with a different vehicle, maybe thinner shielding, no atmosphere—your exposure is greater. And you’re at more risk for solar particle events on a long transit, let’s say to Mars.

Continuing bone loss is also a concern. How do we mitigate that? The exercise devices we have on the station are big. We love them, but can we take something that large on the next vehicle? Probably not. So we’re looking at devices to use on the vehicles that are going to take us farther out.

Then we have the effects on the eyes—the issues that we’ve seen with changes in the shape of the eyeball itself, swelling of the optic nerve, changes in vision. I did not experience any of those, but certainly, we’ve had other astronauts that have. So it’s something we’re tracking; we’re trying to figure out how to predict it and then how can we treat it if it does pop up.

Being a physician, it must have been interesting watching and comparing what happened to you versus your crewmates.

It’s kind of the old adage that until you walk in somebody’s shoes, you really have no idea. But then you realize, also, how different everybody’s bodies are. For example, it takes time to learn how to move gracefully in microgravity. I flew up there with Alex Gerst [of the European Space Agency], and this was his second long-duration flight. And when we first entered the ISS, I very clearly remember him saying, “Wow, my body remembers how to move up here.” His first flight was four years prior to that, but his brain had remembered. There was neural memory in there that said, “When you get up into microgravity, it’s a light touch here, a light foothold here. Just use your toe here to hold yourself down. Push off here, gently.” So he just remembered. To me, that tells you how remarkable the brain is at adapting to new environments.

What makes microgravity such a desirable place for conducting biological science?

Cell growth differs up in microgravity. Scientists are able to culture cells such as endothelial cells [which line the inside of blood and lymphatic vessels] for a little bit longer. They grow in a better, more three-dimensional fashion than growing them on a flat plate on Earth, which allows scientists to study different things.

The other thing that changes is that it’s sort of like a rapid aging process that occurs in orbit. So we look at all the molecular markers and the way cells also change in orbit. And processes that take years on the ground, such as osteoporosis, happen much more quickly up there. So scientists see it as a test bed.

And finally, the third thing that I really enjoyed looking at was protein crystal experiments. Whether it was a protein involved in Parkinson’s disease or a drug that a pharmaceutical company was studying to improve, these protein crystals are structures that grow better [on the ISS]. They grow in a more 3-D, better-ordered structure in orbit, because they’re not limited to that flat 2-D plate. There’s a lack of convective currents in microgravity, which helps those crystals grow. It gives scientists better insight into the protein structure. So if they were able to look at a protein that causes Parkinson’s disease and have 30 percent more insight, or even 20 percent more, they’re able to look at it and say, “Huh, we see a new target for an inhibitor drug” or “We can tweak our drug a little bit and reduce that side effect, because now we’re better able to look at this protein.”

Which medical experiments do you think are the most exciting?

Certainly, the Angiex chemotherapy study we did up there—I spent about six to eight weeks working on that. It was a good chunk of my time on the mission. The scientist was looking at: How did endothelial cells grow? And could we test chemotherapeutic agents on them? And what I want to know from the principle investigator is, “Did the ISS help you create a chemotherapy agent to target a tumor’s vascular supply?” Because that, to us, is important. Cancer is still, and has been for a long time, the emperor of all maladies. And so any small part that we can do to help in that fight, I’ll take it. Because a lot of my patients are dealing with cancer. Everybody’s dealt with cancer in some way, whether it’s a family member, a friend or themselves personally. This is something that everybody’s looking at and interested in solving. I’d love to see more studies like that.

Does your work in space inform how you relate to your patients on Earth?

I talk to my patients about the cancer research. I talk about Alzheimer’s disease a lot, because beta-amyloid protein is involved in many different disease processes. And I say, “Look, we’re getting better insight, through protein crystal growth, into beta-amyloid protein, which means that three to five years from now, we could potentially have better treatments out there.” And they love it hearing about it. They absolutely love it.