Beneath the surface of the Pacific Ocean to the southeast of Japan, there is a very deep, crescent-shaped trench called the “Mariana Trench.” Near the southern tip of the crescent, there is a small slot-shaped area called the “Challenger Deep.”

With a measured depth of approximately 35,797 feet below sea level, a journey to the bottom of the Challenger Deep is nearly seven miles, making it the deepest known place on Earth. To give you an idea of just how deep the Mariana Trench is, if Mt. Everest were placed in the deepest part, there would still be over a mile of water above its peak!

The Challenger Deep is named after a British Royal Navy ship called the HMS Challenger. The Challenger was the first ship to measure the depths of what is now known as the Challenger Deep.

The trench was measured by “sounding,” which involves dropping a very long line with a weight at the end into a body of water. Improvements and advancements in technology have allowed modern scientists and researchers to use sonar to study ocean depths.

Only four descents into the Challenger Deep have ever been achieved. The first was in 1960 by a vessel called the Trieste. The Trieste was a special kind of ship called a “bathyscaphe,” invented by Jacques and Auguste Piccard. The name “bathyscaphe” is taken from the Greek words for “deep” and “ship.”

The Trieste’s journey into the trench took almost five hours, while its return to the surface took three hours and 15 minutes. It remained on the ocean floor for only 20 minutes, due to a crack in a window caused by the extreme pressure.

The second descent into the Challenger Deep was made in 1995 by an unmanned deep-sea robotic probe named Kaiko. Kaiko measured the Challenger Deep at 35,696 feet. Kaiko also collected samples from the bottom of the deep.

The third descent into the Challenger Deep took place in 2009, when the U.S. Navy sent the Nereus on an exploration. The Nereus is a hybrid remotely-operated vehicle, also known as an HROV.

The Nereus spent more than 10 hours at the bottom of the Challenger Deep, sending live video and data back to a ship at the surface. Using a robotic arm, the Nereus also collected geological and biological samples from the ocean floor.

The most recent descent into the Challenger Deep happened in 2012 by solo-diver James Cameron in the DEEPSEA CHALLENGER. He collected film footage, along with photographs and samples of water and deep sea organisms. The project is now in its second phase—scientific analysis of the expedition’s findings.

34 Join the Discussion

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    • Thanks for commenting, Carmen! We thought it was really cool to learn about the vessels that travel that far into the deepest oceans! :-)

  1. so cool. yay. my mom told me to get on here and leave a comment. so here i am. im actually kinda interested. its pretty cool.

    • We’re glad to hear you like visiting Wonderopolis, Jonathan! Thanks for leaving us this GREAT comment to let us know! :-)

  2. Hi, if I know that your company was in Kentucky, I would have visited you because 3 years before I lived in Kentucky, but know I live in Ohio, sorry I didn’t visit you guys. You guys are the best. When my mom tells me to read, I pull out my laptop, go to Wonderopolis and read.


    • Hello, Rithik! It makes us SUPER happy to hear that you choose to visit Wonderopolis and learn new things by exploring our Wonders of the Day® when your mom asks you to read! WONDERing leads to LEARNING, and LEARNING makes us all smarter! Way to go! :-)

  3. Now this is really fascinating, thank you for the information. However, what I found very impressive were the individual responses from Wonderopolis to every single comment. Amazing. I look forward to knowing a lot more stuff from your website. Excellent.

    • We appreciate your kind comments, Noreen. We love hearing from Wonder Friends and responding to them. We look forward to reading more comments from you soon!

  4. How do we know it’s the deepest place? At least Wonderopolis states” deepest known” place, but almost always it’s used as dogma. The fact is that in articles I’ve read, say about searching for the Malaysian airliner that went down, it is admitted that most of the ocean is STILL unmapped (only 5% is mapped, according to recent article I read), yet in the ‘next sentence’ the Mariana Trench is claimed as “the” deepest part of the ocean”. I find this very strange in that the trench was discovered in 1875 with absolutely no modern equipment and the world appears to have all jumped on the bandwagon by sending many sounding expeditions to it for the next 140 years. Like all comfortable statistics, this one makes me uncomfortable. And, I wonder where – truly – lies the deepest place in the ocean.

  5. Again, a very useful post. However, although I know that this is a U.S. website, it may be helpful to give measurements in metric units (even in brackets behind the old “imperial” system). Scientists in the U.S. use metric measurement because they need to share their work with scientists around the world. In addition, the rest of the world has adopted SI as a standard.

    Still, thank you. :-)

  6. Hello Wonderopolis it is just amazing to me that only 3 ships made it to the bottom and how did they wouldnt the water pressure cruch the ship?

    • It truly is amazing, Gabe M! The vessels that were able to reach the bottom were made of special materials that could withstand the enormous pressure of the water. But as the Wonder of the Day points out, even the Trieste’s journey was cut short because of a crack in the window due to the extreme pressure! Thanks for WONDERing with us! :)

  7. This is verry cool verry important I didn’t know this at all now I know thanks to u ,wow this place is verry deep verry good.

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Have you ever wondered…

  • Where is the deepest place on Earth?
  • How deep is the Challenger Deep?
  • What is a bathyscaphe?

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Try It Out

We hope you enjoyed today’s super-deep Wonder of the Day! Keep diving in by exploring the following activities with a friend or family member:

  • Why would scientists be interested in exploring the Challenger Deep? If it’s difficult to reach and very few people will ever go there, why explore it? What do you think they hope to learn? Do you think it’s a place worth exploring? Why or why not? If you were a billionaire and were asked to finance a new trip to the Challenger Deep, what would your response be? Why? Discuss this type of scientific research with your friends and family members. What do they think?
  • What do you think exists at the bottom of the Challenger Deep? Could plants or animals survive at that depth? Why or why not? Do some independent research online to try to find the answers to these questions. Before you jump online, though, form a hypothesis of your own about the answers to these questions, and then see if your research supports your answer.


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