Astronaut Scott Kelly, who just returned from 340 days in space, will retire from NASA

Scott Kelly, the NASA astronaut who just came back to Earth after nearly a year on the International Space Station, is retiring from the space agency on April 1. 

Kelly spent 340 days in space on his most recent mission, allowing scientists to gather a plethora of data about how the human body behaves during long periods in the extreme space environment.

“This year-in-space mission was a profound challenge for all involved, and it gave me a unique perspective and a lot of time to reflect on what my next step should be on our continued journey to help further our capabilities in space and on Earth,” Kelly said in a statement announcing his retirement. 

"I am humbled and excited by new opportunities for me to support and share the amazing work NASA is doing to help us travel farther into the solar system and work with the next generation of science and technology leaders.”

Kelly is currently the record holder for most time spent in space as an American astronaut, with 520 days over the course of four missions, but Kelly hopes it doesn't last.

“Records are meant to be broken,” Kelly said. “I am looking forward to when these records in space are surpassed.”

Before leaving the Space Station, Kelly mentioned that he hopes to remain involved with space exploration in some capacity through the rest of his career, though it is unclear where he will go when he leaves NASA.

Kelly also waxed a little poetic about his time on the Space Station before he left, saying that his yearlong mission would likely be the last time he visits the orbiting laboratory.

"Leaving this amazing facility is going to be tough, because I probably will never see it again," Kelly said before he flew back to Earth. 

"I've flown in space four times now so it's going to be hard in that respect ... I've been up here for a really long time and sometimes, when I think about it, I feel like I've lived my whole life up here."

In spite of the fact that he is leaving his NASA position, Kelly will keep taking part in the research started with his one-year mission on the Space Station. 

Scientists need to continue experiments with Kelly and his twin brother Mark Kelly so that they can learn how to mitigate any potentially harmful effects created by a long journey to Mars or another deep space destination.

“When the first Americans set foot on Mars, they will be following in the footsteps of one of the finest astronauts in the history of the space program, my friend, Commander Scott Kelly," NASA administrator Charles Bolden said in a statement. 

"After spending an American record 520 days in space -- including his Year in Space -- I can think of no one more deserving of some well-deserved rest and time on the same planet as his family and friends," he added.

Kelly has been a NASA astronaut since 1996.