A former United States navy commander identified as Victor Vescovo has become the first person in the world to reach the bottom of all four of the Earth's deepest ocean trenches, marking a significant step in history.

Using the submersible dubbed DSV Limiting Factor, a two-person submersible built by Florida-based company Triton Submarines, Vescovo reached the bottom of the Kermadec Trench located in the South Pacific Ocean. The historic moment happened over the weekend and had the 55-year-old ex-US navy commander completing one of his personal goals.

Deepest Parts of the Ocean

Vescovo spent nine hours during the expedition with a small team that later reached a maximum depth of 32,818 feet, reaching the bottom of the Kermadec Trench. The submersible vessel's cameras recorded footage of "one of the deepest jellyfish ever seen on film" as well as a "brilliant gold" bacterial mat that fed off the minerals and gases found inside the rocks in the area, Dailymail reported.

The jellyfish that Vescovo's team recorded appeared to be a "comb jelly," also known as Ctenophora, and somehow survived being under seven tons per square inch of water pressure. In a Twitter post, Vescovo said that the sea creature would most likely have adapted over a long period to survive in the harsh underwater conditions.

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While talking from his expedition ship, the Pressure Drop, Vescovo said he found exploration such an "extraordinary privilege." He noted that he felt like he was inside a spaceship traveling to an alien world and seeing what no one else has ever seen before, The Times reported.

Vescovo was accompanied by Kathy Sullivan, who has become the first person to visit both space and the deepest place in the ocean. The NASA astronaut and oceanographer visited Challenger Deep on Sunday.

Space and Oceans

Sullivan is the first of the three explorers to finish the mission that lasts for approximately 10 hours, the other two scheduled this week. In an interview, the astronaut said that seeing the place in person was incomparable to data-based understanding.

Since she was a young girl, Sullivan has been fascinated by explorers of the world, following early astronauts, Jacques Cousteau, and the early aquanauts. She called them "inquisitive people" who were clever enough to figure out how to go and make things happen when they wanted.

The NASA astronaut first learned about the Challenger Deep and the Mariana Trench when she was studying in college at the University of California, Santa Cruz. Originally, she planned to study Russian but took a few science classes "quite against her will" that would later change her perception of the ocean forever.

"Suddenly, there was so much history, so many stories of exploration, and then all the knowledge of how the ocean works geologically, the currents and the creatures. It all fascinated me," said Sullivan, CNN reported.

Sullivan then continued her studies at Dalhousie University after being mesmerized by the ocean, where she earned a Ph.D. in geology and focused her research on the North Atlantic. She said that she began to have a passion for planning, designing, and executing expeditions during her studies.

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