Astronaut Mark Vande Hei returned to earth a changed man after 355 days aboard the ISS

A NASA astronaut has come back down to Earth after spending a record-breaking amount of days in space.

And he’s not the same person he was before.

Mark Vande Hei spent a whopping 355 consecutive days on board the International Space Station (ISS).

His body has undergone major changes, some of which are irreversible.

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While in space, Vande Hei was basically a highly skilled guinea pig.

The point of his mission was to learn how the human body reacts to so many consecutive days in zero gravity.

NASA can now use the data to better prepare and care for astronauts in the future.

He conducted a series of studies, including successfully planting a vegetable garden.

Besides growing romaine lettuce while floating in space, Vande Hei also experimented with different meals.

Menu fatigue, caused by eating the same thing every day, is a huge issue for astronauts.

He also provided biological samples to track what changes occur in the body while in zero gravity.

The changes start from the journey to the ISS, which is a relatively short trip at 248 miles.

The force generated at lift-off can hit 3gs, which is three times the gravitational pull of Earth.

An ordinary person would black out under these conditions, but astronauts undergo training and wear special suits to be able to withstand up to 9gs.

Once you’ve pushed past this stage, astronauts will experience weightlessness.

This is the part that looks fun in the movies; flying around and doing somersaults in the air.

In reality, they experience nausea and dizziness as their bodies struggle to figure out what is going on.

Next, Vande Hei’s bones and muscles began to atrophy.

The ISS is kitted out with a special gym, to try and keep muscles active for when the astronauts head back to Earth.

But they’ll still lose 40% or more of their muscle mass.

After six months in space, a human will lose the same amount of bone density as an elderly person would over a decade.

And Vande Hei was up there for nearly a year.

The general rule is that for every month spent in space, he will have to spend two months in recovery.

Once back on land, he’ll be more susceptible to his bones breaking and developing kidney stones.

Let’s hope NASA has given him a generous holiday package.

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