Implosion in the Challenger Deep: Echo Sounding with the Shock Wave

Scott Loranger,David Barclay,Michael Buckingham

doi:10.5670/oceanog.2021.201

Abstract

Since HMS Challenger made the first sounding in the Mariana Trench in 1875, scientists and explorers have been seeking to establish the exact location and depth of the deepest part of the ocean. The scientific consensus is that the deepest depth is situated in the Challenger Deep, an abyss in the Mariana Trench with depths greater than 10,000 m. Since1952, when HMS Challenger II, following its namesake, returned to the Mariana Trench, 20 estimates (including the one from this study) of the depth of the Challenger Deep have been made. The location and depth estimates are as diverse as the methods used to obtain them; they range from early measurements with explosives and stop watches, to single- and multi-beam sonars, to submersibles, both crewed and remotely operated. In December 2014, we participated in an expedition to the Challenger Deep onboard Schmidt Ocean Institute’s R/V Falkor and deployed two free-falling, passive-acoustic instrument platforms, each with a glass-sphere pressure housing containing system electronics. At a nominal depth of 9,000 m, one of these housings imploded, creating a highly energetic shock wave that, as recorded by the other instrument, reflected multiple times from the sea surface and seafloor. From the arrival times of these multi-path pulses at the surviving instrument, in conjunction with a concurrent measurement of the sound speed profile in the water column, we obtained a highly constrained acoustic estimate of the Challenger Deep: 10,983 ± 6 m.

Highlights

Earth is often defined by its extremes: the tallest mountain, the driest desert, the deepest ocean
In March 1875, during the first major expedition devoted primarily to the fledgling science of oceanography, the three-masted sailing corvette HMS Challenger of the Royal Navy discovered a deep depression in the seabed in the western Pacific Ocean—while en route to Guam, the ship had been blown off course to the west and serendipitously tracked over the southern end of the Mariana Trench
While it is generally accepted that the deepest abyss in the ocean is the Challenger Deep, the exact location and the depth of the very deepest spot are still topics of interest to the oceanographic research community

Summary

INTRODUCTION

Earth is often defined by its extremes: the tallest mountain, the driest desert, the deepest ocean. Money, and intellectual energy have been invested in the development of techniques for measuring the deepest depth in the ocean (Gardner et al, 2014; Stewart and Jamieson, 2019), including the development of crewed submersibles capable of making the round trip to the bottom of the Challenger Deep The first such descent was made on January 23, 1960, by the oceanographer Jacques Piccard and US Navy Lt. Don Walsh in the bathyscaphe Trieste (Piccard and Dietz, 1967; Walsh, 2009), whose onboard instruments indicated a depth of 11,521 m, it was subsequently revised downward to 10,916 m.

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Findings

DISCUSSION AND CONCLUSION