The incredible career of NASA's Peggy Whitson, who applied to become an astronaut 10 times before she broke the American record for space travel

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.

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