After travelling space and becoming the first American woman to walk in space, Kathy Sullivan has just achieved another milestone. At 68, she has become the first woman to dive down to the Earth’s lowest point, the bottom of the Mariana Trench in the Pacific Ocean. Sullivan was accompanied by Victor Vescovo, an entrepreneur and deep-sea explorer. They spent about an hour and a half capturing images at Challenger Deep after descending to the spot 6.8 miles down in the Mariana Trench, in a deep-sea research submersible called the Limiting Factor. It’s the only submarine currently able to reach Challenger Deep.

The history-making dive was part of the Ring of Fire expedition organized by Caladan Oceanic, a deep-sea exploration company founded by Vescovo. Sullivan called the International Space Station to share the news when she returned to the ship. She stated, “As a hybrid oceanographer and astronaut this was an extraordinary day, a once-in-a-lifetime day, seeing the moonscape of the Challenger Deep and then comparing notes with my colleagues on the ISS about our remarkable reusable inner-space outer-spacecraft.” She is the only person in history to have visited both space and the deepest point in the ocean.

Vescovo funded the new mission and sent a “big congratulations” to Sullivan in a tweet posted Sunday.

Sullivan participated in several oceanographic expeditions that studied the floors of the Atlantic and Pacific oceans while doing her PhD in Geology from Dalhousie University. She ended up joining the U.S. Naval Reserve as an oceanography officer before becoming an astronaut with NASA. When she eventually left NASA in 1993, she had completed three space shuttle missions and logged 532 hours in space.