What Happens to Astronaut Poop? Look to the Skies!


What will happen to Astronaut Scott Kelly’s body during his year in space? With a nod to Leonardo, NASA diagrams it for us. (NASA)

Do you really need to ask why astronauts are awesome? Well, here are 5 Reasons Why to get you started.

Teachers, scroll down for a quick list of key resources in our Teachers’ Toolkit.

Does this look familiar? The brainiac illustrators at NASA give us an updated (and more anatomically correct!) version of Leonardo da Vinci’s Vitruvian Man. Illustration by NASA
Does this look familiar? The brainiac illustrators at NASA give us an updated (and more anatomically correct!) version of Leonardo da Vinci’s Vitruvian Man.
Illustration by NASA

Discussion Ideas
First, a little background: American astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko are about halfway through the “One Year Mission” on the International Space Station. There are seven key elements of research on the one-year mission.

  1. Functional studies will examine crew member performance during and after the 12-month span.
  2. Behavioral studies will monitor sleep patterns and exercise routines.
  3. Visual impairment will be studied by measuring changes in pressure inside the human skull.
  4. Metabolic investigations will examine the immune system and effects of stress.
  5. Physical performance will be monitored through exercise examinations.
  6. Researchers will monitor microbial changes in the crew.
  7. Researchers will also study the human factors associated with how the crew interacts aboard the station.


The fantastic NASA infographic plots some of the things that will happen to Astronaut Scott Kelly during his year in space. Use our resources to learn more!

  • Kelly will see 10,944 sunrises and sunsets during his year in space. You will see 684. Why do you think he will see more sunrises and sunsets?
    • According to Nat Geo Kids, “The International Space Station barrels around Earth at 27,600 kilometers per hour (17,150 miles an hour)—that means passengers circle the planet every 90 minutes. The astronauts on board orbit Earth so often that they see 16 sunrises and sunsets a day!”





  • The amount of fluid that will shift out of Kelly’s legs and toward his head is equivalent to a 2-liter bottle of soda. Why will his blood shift around in space?
    • Microgravity. “In space, the body no longer experiences the downward pull of gravity that distributes the blood and other body fluids to the lower part of the body, especially the legs. The fluids are redistributed to the upper part of the body and away from the lower extremities. While in space, astronauts often have a puffy face due to this fluid shift and legs that are smaller in circumference. The fluid shift to the head can also lead to a feeling of congestion.”
      • According to Nat Geo Kids, microgravity might even contribute to an astronaut’s growth spurt: “Without gravity, the spine expands. In fact astronauts who spend six months on the International Space Station can grow three percent taller.”


  • Kelly will run about 1,043 kilometers (648 miles) on a specialized treadmill. How is the treadmill specialized for astronauts? Watch our “Space Gym” video to find out.
    • Astronauts “strap in” to a treadmill using a series of flexible bungees. This keeps them on the treadmill and not floating away in microgravity! The treadmill also has strong steel “treads” that won’t break and float away, which would put astronauts and equipment in danger.



  • Kelly will exercise more than 700 hours during his year in space. Besides the treadmill, what other exercise equipment is available to astronauts? Take a look at the “Space Gym” video for some help.
    • Instead of lifting weights, astronauts use an ARED (Advanced Resistive Exercise Device) to build strong muscles. (In microgravity, “weights” don’t actually weigh much of anything!) Astronauts pull against ARED’s vacuum cylinders, which lack air, to create resistance and work their muscles.
    • Astronauts ride a CVIS (Cycle-Ergometer Vibration Isolation System), an unusual stationary bicycle, to help improve their cardio (heart) health. On Earth, we can go for a bike ride or use a regular stationary bike. Astronauts have to “strap in” to a CVIS, because a lack of gravity prevents them from sitting down and staying put. Special shoes also snap into CVIS’ pedals to make sure astronauts don’t just float away.


  • While Astronaut Scott Kelly is in space, NASA will also monitor the health of his brother, retired Astronaut Mark Kelly. Why is this data so valuable to NASA?
    • Scott and Mark are twins, with nearly identical genetics. Comparing their genetic features and responses to similar stimuli helps scientists isolate genetic changes caused by life in a microgravity environment.



NASA: Infographic: What Will Happen to Astronaut Scott Kelly’s Body During His #YearInSpace?

NASA: How Astronauts are Affected by Space Exploration interactive graphic

Nat Geo: 5 Reasons Why Astronauts are Awesome

Nat Geo: Space Gym

NASA: One-Year Mission

National Space Biomedical Research Institute: The Body in Space

5 thoughts on “What Happens to Astronaut Poop? Look to the Skies!

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  2. This is a great little resource, there’s nothing more my kids are interested in than the little details, it lets them get their hooks into a subject

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