In 1984, Kathy Sullivan became the first woman to ever walk in space. Last week, she made history once again as the first woman to travel to the lowest known point of the ocean.

The Challenger Deep, part of the Mariana Trench, is the deepest known part of the seabed. It is nearly seven miles beneath the surface, and it was first reached in 1960 by US Navy Lieutenant Don Walsh and Swiss oceanographer Jacques Piccard. It has only been reached by six other people since this initial expedition, and never by a woman–until now, that is.

Sullivan loaded into a two-person submersible with former naval officer Victor Vescovo and descended more than 35,800 feet into the ocean. It took them between 4 and 5 hours to descend and ascend.

Sullivan believes nations and individuals should continue to push their knowledge about the world, and she also hopes for more diversity and female representation in science. Her voyage represents a giant leap on both of these fronts.