What we know about the ocean's depths — and why it's so risky to explore it – CNN

Editor’s note: Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. CNN  —  The submersible vehicle currently lost at sea is part of a relatively new effort enabling tourists and other paying customers to explore the depths of the ocean, the vast majority of which has never been seen by human eyes. Though people have been exploring the ocean’s surface for tens of thousands of years, only about 20% of the seafloor has been mapped, according to 2022 figures from the National Oceanic and Atmospheric Administration. Researchers often say that traveling to space is easier than plunging to the bottom of the ocean. While 12 astronauts have spent a collective total of 300 hours on the lunar surface, only three people have spent around three hours exploring Challenger Deep, the deepest known point of Earth’s seabed, according to the Woods Hole Oceanographic Institution. In fact, “we have better maps of the moon and Mars than we do of our own planet,” said Dr. Gene Feldman, an oceanographer emeritus at NASA who spent more than 30 years at the space agency. There’s a reason deep-sea exploration by humans has been
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