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Image 1 for How scientists (accidentally) measured the earth’s deepest point underwater

Challenger Deep Sound 2 - north of Papua New Guinea, east of the Phillipines. Pic: Dieter Bevans

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How scientists (accidentally) measured the earth’s deepest point underwater

15 March 22

From These Amazing Oceans File: The history of science is littered with happy accidents. Leave a sample out while you’re on vacation, come back to discover penicillin. Clumsily drop your experiment on a hot stove, create weatherproofed rubber. Shatter a computer chip, invent “smart dust” for environmental monitoring. Now ocean explorers can add their own tale of serendipity to the ledger: Implode your deep-sea recording device, make one of the most precise measurements yet of the deepest point in the ocean. 

David Barclay, then a grad student at Scripps Institution of Oceanography, did not set out to redraw any atlases. He was working on a pair of recording devices that scientists could use to capture marine soundscapes, helping them better understand what’s happening under the sea. In 2014 he had the chance to toss his work overboard into the Mariana Trench—specifically the spot known as Challenger Deep that marks the deepest known point in the ocean (see map).

But as Maya Wei-Haas reports, only one of his creations (pictured above) made it back unscathed. The glass housing around the device called Deep Sound Mark III imploded under the crushing weight of the water; its companion, Deep Sound Mark II, captured audio confirming the catastrophic demise.

Six years later, fellow oceanographer Scott Loranger was stuck in his lab at Woods Hole Oceanographic Institution, unable to do field work due to the COVID-19 pandemic. He dug up the recording hoping to find something useful, and he left the tape running while he typed. That’s when he heard it: the faint ping of sound waves from the implosion bouncing between the ocean’s surface and its dark, hidden depths. Just like a bat using its echolocation to navigate, Loranger and Barclay were then able to use the bouncing sound to measure the distance down to Challenger Deep with stunning precision, yielding a new measurement of 36,033 feet (or 10,983 metres, plus or minus six metres). 

The result adds a crucial data point to previous answers pulled from the various methods used to measure the ocean’s depths. It’s not definitive, but the new measurement is fortuitous because it helps expand the limits of human knowledge, Loranger says: “At its most basic, that’s what every scientist is trying to do.”

 - AUTHOR: VICTORIA JAGGARD Science editor at Nat Geo


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