Context: On June 7, astronaut and oceanographer Kathy Sullivan, who was the first American woman to walk in space in 1984, became the first woman and the fifth person in history to descend to the deepest known spot in the world’s oceans, called the Challenger Deep in the Mariana Trench, which is seven miles below the surface of the Pacific Ocean.
Key Points

• Challenger Deep is the deepest known spot in the world’s ocean in the Mariana Trench, which is seven miles below the surface of the Pacific Ocean.
• She made her descent in the two-person submersible (vehicles that can be operated underwater).
• The expedition aims to observe volcanic vents, identify new species and conduct the extensive mapping of the US Exclusive Economic Zone at the request of the National Oceanic and Atmospheric Administration (NOAA).

About Challenger Deep

• According to NOAA, the average depth of the ocean is about 12,100 feet and the deepest part is called the Challenger Deep, which is located below the surface of the western Pacific Ocean.
• It is approximately 36,200 feet deep.
• The British Ship HMS Challenger discovered Challenger Deep between 1872-1876.
• The first dive at Challenger Deep was made in 1960 by Lieutenant Don Walsh and Swiss scientist Jacques Piccard on a submersible.

Why are scientists interested in deep ocean areas?

• As per NOAA, most of the existing knowledge of the oceans comes from shallower waters, while deeper waters remain relatively unexplored.
• Ocean exploration is disciplined and organized and includes rigorous observations and documentation of biological, chemical, physical, geological, and archaeological aspects of the ocean.
• Finding out more about the deep ocean areas can potentially reveal new sources for medical drugs, food, energy resources and other products.

Significantly, information from the deep oceans can also help to predict earthquakes and tsunamis, and help us understand how we are affecting and getting affected by the Earth’s environment.

About Marian Trench

• The deepest part of the world’s oceans.
• It is located in the western Pacific Ocean.
• It is a crescent-shaped scar in the Earth’s crust.
• The trench is not the part of the sea floor closest to the center of the Earth. This is because the Earth is not a perfect sphere; its radius is about 25 kilometres (16 mi) less at the poles than at the equator.
• The Mariana Trench is part of the Izu-Bonin-Mariana subduction system that forms the boundary between two tectonic plates.
• In this system, the western edge of one plate, the Pacifc Plate, is subducted (i.e., thrust) beneath the smaller Mariana Plate that lies to the west.
• Crustal material at the western edge of the Pacific Plate is some of the oldest oceanic crust on earth (up to 170 million years old), and is therefore cooler and more dense; hence its great height difference relative to the higher-riding (and younger) Mariana Plate.
• The deepest area at the plate boundary is the Mariana Trench proper.
• The movement of the Pacific and Mariana plates is also indirectly responsible for the formation of the Mariana Islands.
• These volcanic islands are caused by flux melting of the upper mantle due to release of water that is trapped in minerals of the subducted portion of the Pacific Plate.