Lifeboat Foundation

She retired from NASA on Friday after blazing a trail for countless female astronauts.

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.”