South Korea's first and only astronaut, Yi So-yeon, has resigned her position, effectively ending the country's space program.

The then 29-year-old bio-engineering student was one of 36,000 Koreans to apply for the position when the Korean government decided to create its own space agency, the Korea Aerospace Research Institute. In 2008, So-yeon made history when she spent 11 days on the International Space Station, becoming the first Korean and 49th woman in space.

She was delivered to the space station via Russia's Soyuz spacecraft; Korea reportedly paid Russia $20 million for the trip.

Now 34 years old, So-yeon is pursuing an MBA degree at UC Berkley's Haas School of Business. "California is an easy place to be an Asian woman engineer," she recently said of her experience at Haas. "It feels like home."

But studying business and being astronaut was apparently too much for So-yeon. Officials at the Korea Aerospace Research Institute confirmed this week that So-yeon had mailed a letter informing the agency of her decision to resign her post, citing "personal reasons."