She was the first American woman to walk in space. Now she's made history, again.

Doha Madani

Kathy Sullivan, America’s first female spacewalker, also became the first woman to reach the deepest known point of the ocean.

Sullivan dove to the bottom of the Challenger Deep and safely returned in her submersible vessel on Monday, according to EYOS Expeditions, the company that operated her expedition. She is now the eighth person to reach the depth, the lowest point in the Marianas Trench, which is about 35,853 feet under the Western Pacific Ocean surface.

A call was made between Sullivan’s vessel at the bottom of the ocean and astronauts aboard the International Space Station. The call was an homage to Sullivan’s other historic adventure, when she became the first American woman to walk in space in 1984.

Astronaut Kathryn D. Sullivan, 41-G mission specialist, uses binoculars for a magnified viewing of Earth through Challenger's forward cabin windows on Oct. 6, 1984. (Johnson Space Center / NASA)
Astronaut Kathryn D. Sullivan checks the latch of the SIR-B antenna in the space shuttle Challenger's open cargo bay during her historic extravehicular activity (EVA) on Oct. 11, 1984. (NASA)

“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 press release.

Expedition leader Rob McCallum said it was amazing to set up the call between the two “spacecrafts.”

“Two groups of humans using cutting edge technology to explore the outer edges of our world,” McCallum said. “It highlighted the vast span of human endeavor while at the same time linking us close together as fellow explorers.”

The first two people to reach the Challenger Deep, located in the south end of the Mariana Trench about 190 miles southwest of Guam, were Don Walsh and Jacques Picard in 1960.

Dr. Kathy Sullivan and Victor Vescovo reviewing the plans before their dive to Challenger Deep. (Enrique Alvarez / EYOS Expeditions)
Kathy Sullivan just completed her historic dive to become the first woman to reach the deepest point in the ocean and the first human to have been in space and at full ocean depth. (EYOS Expeditions)

Victor Vescovo reached the bottom last year as part of an expedition team that made five dives in the Mariana Trench over the course of a week. Vescovo described the trench as “very peaceful” in an interview with Live Science last year.

“Honestly, toward the end, I simply turned the thrusters off, leaned back in the cockpit and enjoyed a tuna fish sandwich while I very slowly drifted just above the bottom of the deepest place on Earth, enjoying the view and appreciating what the team had done technically,” Vescovo said.

"Avatar" and "Titanic" filmmaker James Cameron broke the record for deepest solo dive in 2012 when he became the first person to reach the Challenger Deep alone.