The first American woman to walk in space in 1984 is now also the first to travel to the ocean’s Challenger Deep, the lowest point on Earth.

Oceanographer and astronaut Dr. Kathy Sullivan participated in EYOS Expeditions’ mission to the Mariana Trench in the western Pacific Ocean, 200 miles southwest of Guam, on Sunday. Sullivan is the eighth person in history to successfully make the trip. 

Explorer Victor Vescovo dove almost 36,000 feet –– nearly seven miles –– with Sullivan in the Limited Factor submersible. The two spent about an hour and a half capturing photos of the ocean’s depths. 

“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,” Sullivan said in a statement.

Sullivan joined the National Aeronautics and Space Administration (NASA) in 1978, as part of the first group of US astronauts to include women. 

Vescovo praised Sullivan for being the first woman to reach the bottom of the ocean, according to the New York Times.

36 years after my space walk, I became the first woman to dive to the deepest known spot in the ocean - the Challenger Deep. #WorldOceansDaypic.twitter.com/KWJxx4fBYR

— Kathy Sullivan (@AstroKDS) June 9, 2020

Sullivan’s achievement is a major feat for women in the male-dominated field.

Deep-sea exploration allows scientists to collect invaluable information to understand the human impact on the earth, research new medical drugs, and more. Gender barriers such as bias, unsafe work environments, and lack of support, however, have historically held women back from contributing to the world’s understanding of the ocean. The gender gap for physical oceanographers in tenure-track positions has doubled since the 1990s, leaving fewer women teaching the subject at a professor level. 

The lack of female representation in marine science reflects a larger disparity in science, technology, engineering, and mathematics (STEM). United Institute for Statistics reported less than 30% of the world’s researchers working in science are women. 

While the number of women in marine science has increased, there are efforts to ensure women and girls are even more represented. The Intergovernmental Oceanographic Commission of UNESCO (IOC-UNESCO) is working to promote equal representation in marine science and champion women’s accomplishments to show young girls what they can achieve. 

Sullivan’s latest mission showed women do not have to settle for one dream. Before NASA, Sullivan always intended to work toward exploring the Challenger Deep.  

“My specific aspiration through all of graduate school was to ... be able to actually go down and see the deep-sea floor myself, do the volcanology part of marine geology and geophysics, and get to dive,” she said in 2007.