NASA astronaut Scott Kelly, left, and his twin Mark get together before a press conference in Houston, Texas, in 2016. Mark was retired as an astronaut but agreed to be part of the twins study. (AP)

NASA astronaut Scott Kelly, left, and his twin Mark get together before a press conference in Houston, Texas, in 2016. Mark was retired as an astronaut but agreed to be part of the twins study. (AP)

Scott Kelly takes a photo of himself inside the Cupola, a special part of the International Space Station which provides viewing of the Earth and the station. (AP)

Scott Kelly takes a photo of himself inside the Cupola, a special part of the International Space Station which provides viewing of the Earth and the station. (AP)

Scott Kelly participates in a spacewalk outside the International Space Station in 2015. (AP)

Scott Kelly participates in a spacewalk outside the International Space Station in 2015. (AP)

NASA astronaut Peggy Whitson floats aboard the International Space Station. Can you tell which way is up? (AP)

NASA astronaut Peggy Whitson floats aboard the International Space Station. Can you tell which way is up? (AP)

Scott Kelly, right, and his twin brother Mark Kelly attend an event at the elementary school they attended in West Orange, New Jersey, in 2016. (AP)

Scott Kelly, right, and his twin brother Mark Kelly attend an event at the elementary school they attended in West Orange, New Jersey, in 2016. (AP)

Made for Gravity

Posted: November 1, 2020

When God created people, He placed them firmly on planet Earth. Their bodies are designed to flourish in an environment where gravity holds them down. So when people go to space, they have a lot of adjusting to do.

People in space don’t experience gravity the same way they do here. Their bodies relax. They float. Sense of balance grows confused. (That’s why all the writing inside spacecraft faces the same direction—so astronauts remember which way is up!) In one sense, the weightlessness felt in space really takes a load off. In another sense, it totally wears people out.

Why? Moving to zero-gravity affects hand-eye coordination. It causes motion sickness and changes the way people move. On Earth, human bones and muscles have to support the weight of the body. In space, people are weightless. Bones and muscles don’t have to push against gravity. They grow weak. They lose density. Astronauts must exercise for two hours each day in space just to keep their bodies from deteriorating.

Astronauts face other problems too. Body fluid moves toward their heads, putting pressure on their eyes. This can cause vision problems. Calcium flows out of their bones. They can easily grow dehydrated and develop kidney stones. Medications even react differently to bodies in space.

Compare twin astronauts. The first one, Scott Kelly, takes a one-year mission to the International Space Station. That’s twice the amount of time astronauts normally spend in space. Mark Kelly, Scott’s twin brother, stays on Earth. Like all astronauts, these two are in great physical shape. But space treats Scott roughly. When he returns to Earth, scientists compare him to Mark. Scott’s telomeres—chromosome parts that slow down aging—have grown shorter. (Newsflash: Space actually makes you old!) He thinks less clearly and quickly than he used to. His bones are less well-formed than his brother’s.

Scientists hope astronauts will soon be able to travel to Mars. Those journeys could last at least three times longer than Scott Kelly’s. Could “mighty mouse” treatment make Mars missions possible?