At 35,853 Feet Down, an Argument About ‘Deepest’


How deep is the deep end of the ocean? The answer turns on an array of factors nearly as wide as the sea itself: the barometric pressure over the site in question, the seawater’s density and temperature, the vagaries of measurement and, perhaps, on whether a world record is at stake.

The whereabouts of the planet’s deepest spot is widely agreed upon: the Challenger Deep, a muddy depression nearly seven miles down in a long fissure of the western Pacific, 200 miles southwest of Guam. The depression is estimated to be roughly a mile wide and seven miles long.

In April, Victor L. Vescovo, a rich investor who has skied the North Pole and climbed Mount Everest, piloted a submersible — part of a $48 million operation — into the Challenger Deep and declared his dive the deepest ever by a human. Global headlines followed. The record depth was given as 35,853 feet — a first by 52 feet, according to the team’s official statement.

Last month, Mr. Vescovo raised his profile further by making the final dive of what his team called “the world’s first manned expedition to the deepest point in each of the five oceans,” a list that includes the Challenger Deep. The Discovery Channel will feature the dives in a five-episode series.

Mr. Cameron likened the issue to an Everest climber claiming to have bested another mountaineer even though both reached the same summit.

“You can’t go deeper,” he said of the Challenger Deep. “It’s flat and featureless. So his gauge may read differently from mine, but he can’t say he’s gone deeper.” What’s irksome, Mr. Cameron added, “is that something can become part of the public record without substantiation.”

That is especially so in the Challenger Deep. The sonic impulses from a surface ship must travel through many layers of seawater of differing composition before bouncing off the bottom and returning to the surface for analysis and interpretation. The path, by one measure, goes from warm to icy to warm again.

Typically, depth measurements of the Challenger Deep are recalculated and often revised. The New Hampshire scientists told of a preliminary 2011 estimate that they were updating in their 2014 paper. The revised figure was 33 feet shallower.

“Perhaps we will never know,” he said in a follow-up email. “All I can do is stand behind the actual data.”



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