NASA Astronaut, Scott Kelly, Retires After Yearlong Mission in Space

Scott Kelly, NASA astronaut, set an unbeatable record when he completed his yearlong mission at the International Space Station, becoming the only American to spend the maximum time in space. On April 1, he officially retired from his duty as he handed over his spacesuit. The astronaut looked back at his experiences and accomplishments in a video interview.

"When we do things that are really hard, we can achieve great things - and that has worked as a great model for me," Kelly said in the interview, which was conducted March 25 during a trip to Russia to commemorate the one-year space mission with cosmonaut Mikhail Kornienko. (Kelly referred to fellow one-year crewmate Kornienko as his "brother from another mother," and said the pair will remain lifelong friends even if Kelly never gets back to Russia again.)

"#ThankYou, @NASA! It's been an incredible 20 years! #YearInSpace," Kelly, who was selected as an astronaut for NASA in 1996, said on his Twitter post March 31.

Even though Kelly is no longer associated with NASA, he will still be associated with the space agency. For now, Kelly is undergoing tests to determine the impact of long spaceflight on his body. Mark, Kelly's brother, a former NASA astronaut, is also being tested. Mark was on the ground when Scott was in space and the researchers are examining the identical twins to recognize any genetic changes that the spaceflight may have resulted in Scott.

According to a documentary chronicling Scott Kelly's ordeal in the space, the one-year mission had witnessed its own set of challenges. Soon after Kelly's arrival, two cargo ships failed to reach the orbiting laboratory. Had there been another failure, the crew may have had to ration their food.

Kelly spent a total of 520 days orbiting in space across four missions. His first flight lifted off in 1999 and the last one was a month back. "Going to Mars is a bunch of baby steps, and it started off with the first human in space, Yuri Gagarin," Kelly said in the video interview.

The one-year mission is "another one of those steps," he added. "I'm proud to be a small part of that."