The first American woman to walk in space, Kathy Sullivan, just became the first woman to reach the deepest point of the ocean

Sullivan dived 7 miles deep with millionaire adventurer Victor Vescovo , into the Pacific Ocean's Mariana Trench .
The 68-year-old became the eighth person in history to make the dive.
Sullivan was the first US woman to walk in space in 1984, and she served as the administrator of the National Oceanic and Atmospheric Association from 2014 to 2017.
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Sunday marked the second time Dr. Kathy Sullivan has made history.

Nearly 25 years after she became the first US woman to walk in space, Sullivan became the first woman to ever reach Challenger Deep, the deepest point in our planet's oceans. She's the only person ever to do both.

Challenger Deep lies nearly 7 miles below the Pacific's surface, within the Mariana Trench about 200 miles southwest of Guam.

Sullivan is only the eighth person in history make the dive, according to EYOS Expeditions, the company coordinating the mission.

The 68-year-old co-piloted a submersible called the Limiting Factor with millionaire adventurer and investor Victor Vescovo.

"Big Congratulations to her!" Vescovo tweeted after their successful mission.

The first thing the two did after they got back to the surface was call the astronauts on the International Space Station.

Victor Vescovo. Tamara Stubbs / Limiting Factor

"As a hybrid oceanographer and astronaut, this was 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.

The challenges of getting to Challenger Deep

Sullivan and Vescovo spent roughly 10 hours aboard the Limiting Factor, a two-person submersible built by Triton submarines and Caladan Oceanic.

It took four hours to descend to the crushing depth of 35,810 feet. They spent 1.5 hours on the ocean floor, then another four hours ascending.

"This is the most exclusive destination on Earth," Rob McCallum, a founding partner of EYOS, said in a March statement announcing the mission. "More people have been to the moon than to the bottom of the ocean."

This was Vescovo's third trip to Challenger Deep, which is more than a mile deeper than Mount Everest is high.

Underwater Limiting Factor hitting the bottom - Mariana Trench. Five Deeps Expedition

At those depths, the water is perpetually dark and barely above freezing. The pressure is a skull-crushing 8 tons per square inch about 1,000 times the pressure at sea level.

According to Sullivan's blog , visiting Challenger Deep subjects Limiting Factor's hull to a pressure "akin to the weight of 291 jumbo jets or 7,900 double-decker buses."

The sub's 3.5-inch thick titanium alloy hull is designed to withstand those pressures, and it has successfully done so during five previous trips to Challenger Deep. It's the only submersible ever created that can make that dive more than once.

The Limiting Factor submarine. Tamara Stubbs / Five Deeps Expedition

A legacy of science and exploration

Sullivan is used to working in high-pressure situations. During her 15-year career with NASA, she flew on three space-shuttle missions, including the one that deployed the Hubble Space Telescope.

kathy sullivan sally ride challenger Space Frontiers/Getty

She was one of the first women selected for the NASA astronaut corp in 1978, and she became the first American woman to walk in space on October 11, 1984, outside the Challenger shuttle.

After her days as an astronaut ended, Sullivan pursued her passion for oceanography and was appointed as the chief scientist of the the National Oceanic and Atmospheric Association (NOAA) in 1993.

Kathy Sullivan NOAA Mark Wilson/Getty

From 2014 to 2017, she served as the administrator of NOAA.

NOW WATCH: What's inside the Mariana Trench