Mariana Trench, 11 000 m under the sea

The Mariana Trench is the deepest place on earth.

Remotely operated vehicle Deep Discoverer, Image courtesy of NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas

Updated on June 26, 2023

Nearly 30 dives since the first in 1960 and scientists and explorers discovered that even there, life exists!

However, the deep sea is arousing more and more interest: after space, will its exploration be the next human conquest?

The Mariana Trench, like a journey to the centre of the Earth

To date, the Mariana Trench in the northwest Pacific is the deepest oceanic trench and the deepest place in the Earth's crust: in 2014, the maximum retained depth was 10,984 m ± 25 m.

The trench is located in a zone where the Pacific tectonic plate passes under the Philippine plate.

However, this oceanic trench was discovered in 1875 during the first oceanic campaign carried out on board the Royal Navy's HMS Challenger, which was tasked with mapping the ocean floor.

Did you know? At that time, measurements were taken using ropes!

Since then, the Mariana Trench has been measured several times by echo sounding, ROV or bathymetric depth-finder, with results ranging from 10,900 to 11,034 metres in depth.

More men on the Moon than at the bottom of the ocean!

Moon - 12 / Mariana Trench - 27: in fact, 12 men walked on the Moon and 27 people dived into the deepest part of the ocean.

In January 1960, nine years before the first man on the moon, the Swiss Jacques Piccard and the American Don Walsh reached the bottom of the Challenger Deep in the Trieste bathyscaphe at a depth of 10,916 m.

And then surprise! The two explorers saw shrimps and an unknown flatfish. Therefore, marine life can exist at a depth where the pressure is a thousand times greater than at sea level.

Mankind has since conquered Space and walked on the Moon, but few have been able to visit the bottom of the oceans.

In 2012, James Cameron, the American director of Titanic, descended alone aboard the Deepsea Challenger to explore the Mariana Trench at 10,898 m.

American explorer Victor Vescovo broke the record by descending to 10,928m in 2019. Although he was able to admire this lunar-like underwater landscape and discover new species, he also saw some waste, notably a plastic bag. He holds the record with 14 dives to date!

Hamish Harding, recently lost in the implosion of the Titan submarine, held the record for dive time (4 h 25) and crossing time (4.6 km) in 2021.

Why dive so deep?

In 2020, two male scientists and a female scientist from China journeyed down to 10,909 metres aboard the Fendouzhe.

The purpose of this dive was to bring back samples and map the bottom of the trench. These missions also aimed to learn about the species and their distribution at these depths.

In 1960, the discovery of marine life at such depths led to the abandonment of the idea of using the trench as a nuclear waste dump!

Today, deep exploration for rare materials could be the next step in the conquest of the seabed.

In brief

Some facts about plastic pollution in the deep sea:

  • The Deep-Sea Debris Database, which contains 30 years of observation data, was launched in 2017.
  • Plastics are widely dispersed even at depths >6000 m and 92% were disposable products.
  • Disposable plastic has reached the world's deepest ocean trench, at a depth of 10,898 mm.
  • Associations between plastic and biota have been detected, particularly in cold seep communities.
  • Deep-sea plastic density in the North Pacific ranged from 17 to 335 articles km-2.

Source : Human footprint in the abyss: 30 year records of deep-sea plastic debris

Préserver les grands fonds

Ces grands fonds marins abritent des ressources qui éveillent de plus en plus l’intérêt et les convoitises des états et des entreprises privées. 

L’exploitation des minerais qui se situent en haute mer sont au cœur de discussions entre pays dans un contexte lié à la transition énergétique mais cette activité ferait courir des risques importants sur ces milieux vulnérables et essentiels au niveau écologique. 

Mobilisons-nous pour protéger les grands fonds marins !

Nausicaá soutient la position de la France contre l’exploitation minière des grands fonds marins et utilisera tous ses moyens pour sensibiliser et mobiliser le plus grand nombre à la réalisation d’un moratoire.

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