Takeaways from Scott Kelly's year in space

After whirling through space for a year, astronaut Scott Kelly came home with a million-plus followers on Twitter, Instagram and Facebook, proving the rocket man for the Reddit generation could inspire.

Asked about what he would miss about space, he said, "It's like why I wanted to be a [Navy] pilot and land on aircraft carriers — because I knew it was hard, there were risks, and it was important, and therefore, for me, rewarding."

He added he would "never be done with space." Here's a look at his mission, from a science and health perspective.

Kelly returned to Earth a tad taller, with poorer eyesight and a slightly smaller heart. While he lost the 1.5 inches he gained in space almost as soon as he stood on solid ground, other effects lingered. His sense of touch is more sensitive right now, and his skin "feels like it's burning" when he sits in a chair.

His mission's chief goal was an experiment in analyzing the physical and psychological effects of long-term spaceflight in anticipation of an eventual manned mission to Mars. Kelly's identical twin, Mark, a retired astronaut, served as a control for NASA.

Scientists and doctors will look at everything from aging, which Scott is likely to have done faster than Mark, to the effects of radiation on the body without the protection of the Earth's ozone layer to how microbes in the twins' guts changed.

The 52-year-old New Jersey native now holds the American record for longest stay in space. He flew 144 million miles on his nearly yearlong voyage, took part in three spacewalks and performed more than 400 scientific studies, from the macro (dark matter) to the micro (stem cells), with forays into vegetable growing. He even grew zinnias.

Kelly has become a celebrity for his record-breaking flight, but he remains humble. "I also want to say this was not my flight. They've talked about my year in space, it's not my achievement, it's NASA's achievement and it's our country's achievement."