Why astronaut Scott Kelly grew 2 inches during his year in space

Astronaut Scott Kelly is back on American soil after an eventful year. 

Kelly spent 340 days aboard the International Space Station before making it back to Earth on Tuesday. During his time up there, he grew plants, conducted experiences, took breathtaking pictures and... grew two inches taller.

In large part, Kelly's year in space was meant to see how our bodies handle that much time in microgravity. One of the things that can happen? Astronauts aboard the ISS grow up to 3% taller, likely because the spine has a chance to elongate with less pressure from gravity.

But, unfortunately for Kelly's newfound height, the effect is only temporary. Once he's back on Earth for a long enough time (still to be determined, but scientists estimate it can take few months), gravity will bring him back to his normal height. 

In 2013, NASA launched a study that wanted to figure out what it was that caused astronauts to elongate by focusing on the spine. There are still some ongoing studies on the topic.

Now that he's back, Kelly will be studied by scientists to look for other changes that may have happened to his body while in space, including any changes to his vision, bones, and brain. Knowing what happens to the body when it's in microgravity for a long time will give researchers clues for how they should prepare astronauts for even longer missions (like a trip to Mars, for instance). 

Watch Kelly arrive back to Houston, Texas: