NASA's Scott Kelly is back in the U.S., after a year in space

The man who set the record for the most consecutive days in space by an American made it home to the U.S. on Thursday.

Astronaut Scott Kelly, who landed in Kazakhstan from the International Space Station on Tuesday, touched down at Ellington Field in Houston at around 2.15 a.m. ET. Kelly and his identical brother, Mark Kelly — who is a retired fellow astronaut and husband to former U.S. Rep. Gabrielle Giffords — will be examined by NASA doctors.

Scott Kelly's adventure in the skies was part of a study of twins. Mark remained earthbound for his part of the study, that will allow scientists to pinpoint the effects of space travel on the human body in preparation for a crewed mission to Mars. Specifically, NASA is looking at the effects of space radiation, as well as the effect of long-term isolation on mental health.

One obvious change for Kelly was that he came back 2 inches taller than his brother because a lack of gravity causes spinal disks to expand.

Inspiring tweets from Scott Kelly's #YearInSpace

Vice President Biden's wife, Jill, joined Mark, and a group of students on a tour of NASA's Mission Control Center — as well as a full-scale model of the International Space Station — as they awaited Kelly's arrival. Mark Kelly said his brother was anxious to get home and joked that he still hadn't showered since returning.

“It’s been a long trip,” Scott Kelly said after arriving in Houston.

“When I left here in February I was 50 and now I’m 52. It’s great to be back in Texas, on U.S. soil. It’s an unbelievable feeling to be back here on Planet Earth, back in our great country and back with all my family and my friends.”

He paid tribute to people including is girlfriend Amiko, daughters Samantha and Charlotte, brother Mark and the rest of his family and friends. He also paid tribute to Biden and NASA  Administrator Charles Bolden.

Welcoming Kelly home, Jill Biden said: "You’re truly an inspiration to all of us. I brought you some beer and apple pie, nothing’s more American than that.”

President Obama called Kelly Wednesday to welcome him back to Earth and to thank him for "inspiring a new generation of young people" to pursue careers in math and sciences. Obama said the data from Kelly's trip will help achieve his vision of sending American astronauts to Mars by the 2030s.

Contributing: William Cummings and Melanie Eversley