What Will Astronaut Scott Kelly's Year in Space Teach Us?

Astronaut Scott Kelly finally returns to solid ground after a NASA record-breaking 340 days in space. His epic journey—with the help of a comparison study of his twin brother!—will be a critical step toward our understanding of the toll space takes on the human body and ultimately toward sending humans on longer missions to Mars. 

Sabrina Stierwalt, PhD
3-minute read
Episode #182


Today Astronaut Scott Kelly returns to solid ground after 340 days in space – an impressive 125 days longer than the previous record for a NASA astronaut. This is Kelly’s fourth trip to space and brings his total time spent away from Earth to 520 days. Accompanying him on his so-called One-Year Mission is cosmonaut Mikhail Kornienko who has been collaborating with Kelly on their research conducted throughout the trip. You can check out the countdown clock to their expected landing near Kazakhstan, as well as a live video feed of their return, on NASA’s website.  

So what have they been doing for all this time?

Preparation for a Mission to Mars

For the past 11 months, Kelly has spent his time on board the International Space Station tracking his emotional and physical health. A mission to Mars is expected to take ~30 months so the One-Year Mission is a crucial step toward understanding the toll this will take on human travelers, both mentally and physically.

My favorite aspect of the experiment, the one that makes it so unique and provides the most potential for giving us important answers, is that the same tests have been taken by retired NASA Astronaut Mark Kelly, Scott Kelly’s twin brother!

As many scientists—and those who may remember high school biology—know, it can be very hard to find a good control sample for your experiment. So every time Scott Kelly took a biological sample in space (think saliva, blood, urine, and poop), his twin brother Mark took the same sample, down here on Earth.

In fact, the biological tests began a full year before the astronaut and cosmonaut even left to start their trip. With these samples and tests serving as baselines, Kelly and Kornienko have been testing themselves throughout their year in space to assess the mental and physical toll on the human body due to the combination of microgravity, increased radiation, and isolation in space. The lack of the full tug of gravity we feel here on Earth has been known to affect bone density, and muscle strength, which both weaken due to lack of use. Since the heart no longer has to pump as hard to push blood to the legs, it also can weaken and even shrink. Fluids, no longer being pumped to the legs, can also then gather in the face, a swelling that can adversely affect vision. Even our gut microbiome can suffer!

And those are just the physical effects of being in space ...


About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.

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