Spending a year in space changes a man. Specifically, it adds 1.5 inches.

That's at least one striking change that astronaut Scott Kelly discovered when he returned to Earth this week after 340 days aboard the International Space Station.

The growth was expected, and it's only temporary, NASA's Jeff Williams told CNN.

"Astronauts get taller in space as the spine elongates," Williams said, "but they return to preflight height after a short time back on Earth."

astronaut Scott Kelly gives thumbs-up after landingScott Kelly rests in a chair outside of the Soyuz TMA-18M spacecraft just minutes after he and Russian cosmonauts Mikhail Kornienko and Sergey Volkov landed in a remote area of Kazakhstan. (Photo: NASA/Bill Ingalls)

Kelly and Russian cosmonaut Mikhail Kornienko landed March 1 in Kazakhstan and then traveled to Houston, where Kelly reunited with his twin brother, former astronaut Mark Kelly.

The 52-year-old brothers are part of NASA's Twins Study. The study involves 10 different experiments from a dozen research institutions as NASA learns how identical twins compare after a year spent in two very different environments.

According to the Los Angeles Times, several of the studies have asked for samples from both brothers, including blood, urine, feces, cheek cells and spit.

"One of the studies looks at how the immune system responds to flu vaccines given at different points in time. Other research examines the telomeres that sit at the end of strands of DNA, in search of signs of aging and stress. There is even a psychological study that examines a strange phenomenon known as "space fog" — a lack of alertness reported by multiple astronauts."

Comparing the brothers will help researchers determine what sort of impact a year in space had on Scott Kelly's body — other than his short-lived extra height. (That increase, by the way, was incorrectly reported as 2 inches initially, but Kelly cleared that up the next day.)

Documenting his return

When he was in space, Kelly shared lots of gorgeous photos and tweets from aboard the ISS, including his antics scaring his fellow astronauts while dressed in a gorilla suit.

Now that he's on solid ground, he's rediscovering the Earth and sharing his latest adventures.

Like a sunrise he saw in Norway:

And he shared a conversation with President Obama who called to congratulate him on his record-breaking mission.

And to prove that astronauts are mere mortals too, he even posted a photo of his lunch.

Before he headed back to Earth, Kelly told reporters in a news conference that he was looking forward to going home and jumping in his pool. After a year in space, the water probably felt great.

Mary Jo DiLonardo covers a wide range of topics focused on nature, health, science and anything that helps make the world a better place.

Astronaut Scott Kelly grew 1.5 inches in space
After a year in space, astronaut Scott Kelly is back on Earth, and scientists are eager to study how he has changed.