NASA astronaut Peggy Whitson, the 58-year-old from Iowa farm country who spent a record-breaking 665 days in space, retired from the space agency on Friday.

"I have hit my radiation limit," Whitson told Business Insider during a recent interview. "So not going into space with NASA anymore."

That realization is both melancholic and exciting for the biochemist, who only half-jokingly admits she's still not sure what she's going to do "when I grow up."

It's an ironic statement from someone who has logged more time in space than any other American, and was the first woman to command the International Space Station.

"It’s been the greatest honor to live out my lifelong dream of being a @NASA Astronaut," Whitson wrote on Twitter Friday, announcing her retirement.

To date, exploring space is an honor she shares with less than 60 women. Whitson sometimes gets tears in her eyes when she reflects on the fact that she will most likely never see space or float above her home planet again.

Regardless of what she decides to pursue next, take a look at what the trail-blazing astronaut has accomplished so far.

17 PHOTOS The incredible career of NASA's Peggy Whitson See Gallery The incredible career of NASA's Peggy Whitson Peggy Whitson grew up on a farm in rural Iowa. When she was a senior in high school in 1978, she learned that NASA had recruited its first female astronauts. For the first time, Whitson thought her dream of becoming an astronaut might be "realistic and achievable."

(NATALIA KOLESNIKOVA/AFP/Getty Images) Whitson started her career with NASA in 1986 as biochemist. She applied to be an astronaut 10 times before finally getting selected. She began training in 1996 and served on her first space mission in 2002.



(DMITRY KOSTYUKOV/AFP/Getty Images) Reflecting on her numerous rejections, she told The Week: "You have to work to make things come into reality. In the end, because I enjoyed what I was doing along the way and was learning so much, I think I was a much better astronaut because of it. Even if, at the time, I certainly didn't agree."



(REUTERS/Mikhail Grachyev) After Whitson first went to space in 2002, she went on to break a ton of records. She's the NASA record-holder for most time spent in space: a whopping 665 days. Only seven Russian cosmonauts have spent more time off of Earth. (SERGEI ILNITSKY/AFP/Getty Images) Whitson also holds the record for the longest space flight any woman has ever taken: 289 days. (NASA TV / Reuters) She has spent more time doing space walks than almost anyone, too: Whitson spent a total of 60 hours and 21 minutes in the vastness of space outside the ISS. Only three other people have been outside in space for longer than that. (NASA TV / Reuters) She told Business Insider that on one space walk, when she was working on an array of solar panels, she caught a glimpse of herself. "I could see myself in a space suit, I could see the Earth behind me in the solar arrays, and I was like, 'holy cow, I really am an astronaut!' Because you forget. You're in this moment. You're getting a job done," she said.

(REUTERS/Yuri Kochetov/ Pool) Whitson was the first female commander of the International Space Station. She said she was never scared to go into space, but being commander felt different. "You're responsible for crew safety, and the safety of the vehicle, so, you know, it ups the stress level a little bit," she said. "We train for all the really bad-day scenarios, which I think helps you prepare." (Shamil Zhumatov / Reuters) She was also the first woman to be named chief astronaut at NASA, the most senior leadership position in the agency for active astronauts. The chief astronaut leads the astronaut corps and serves as the NASA administrator's advisor on all aspects of astronaut training. (Shamil Zhumatov / Reuters) There's one more record Whitson doesn't like to brag about: she is the oldest woman to ever fly in space. She was 57 when she returned from her last trip on the ISS. (REUTERS/Kevin Lamarque) Whitson said the thing she misses most about being in space is the floating. But that wouldn't be fun without a good crew. "The job on orbit is incredibly satisfying and gratifying," she said. "Being a part of a team, that has a meaning so much more than one person." (REUTERS/Maxim Zmeyev) But one thing she does not miss is using the bathroom in space. Whitson revealed to Business Insider that she occasionally had to put on a rubber glove and pack the poo down to keep it from floating away on the ISS.



(Universal History Archive/ UIG via Getty Images) She also doesn't miss the food, which is on a 16-day rotation cycle. "The motto 'it's all about the sauce' really is true, because it all kinda starts tasting the same after a while," she said. (NASA TV / Reuters) Living in space also required a lot of upper-body strength. "We go everywhere on that space station with our hands," she said. "Everything's very hand intensive, so your hands do have a tendency to get very tired." NASA astronauts work out two hours per day on the ISS to maintain bone and muscle mass and counteract the effects of living in zero gravity. After the weightlessness of space, Whitson said life on Earth feels heavy. (NASA TV / Reuters) She believes that we must continue exploring and improving life in space. Whitson is hopeful that future experiments on the moon will help prepare us for life on Mars, regardless of who the first explorers of the red planet turn out to be. "I don't really care who it is, I just think we need to get there," she said. (Photo by John Lamparski/WireImage) It's clear that she's not done exploring, though. "I'm working on an idea for when I grow up," she told Business Insider last month. "I haven't decided yet exactly." (REUTERS/Sergei Remezov) Whitson wants to ensure that others have the chance to leave this planet, too. "I hope that in the near future, everyone's going to have a lot more opportunities to be in space," she said. "It's a very special experience to see the Earth from above. It gives you a new perspective on what home is." (REUTERS/Kirill Kudryavtsev) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

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