Deep beneath the Pacific, 11 kilometers down, lies the Mariana Trench — Earth’s deepest gap and a place wrapped in mystery. Its remoteness has fueled legends for generations, drawing the curiosity of scientists and explorers alike.
The trench emerged into human knowledge during the era of bold oceanic discovery. The Challenger Expedition, begun in 1875, sought to measure just how deep the Pacific could go. Using a simple ballast line and rope, the crew began their descent. The first drop set a record at 8,188 meters, yet later discoveries showed there was far more to learn beneath the waves.
The name Mariana Trench comes from its proximity to the Mariana Islands, which themselves honor Mariana of Austria, wife of Philip IV of Spain. This far-flung region became a symbol of the unknown ocean depths that captivated readers and researchers alike.
When exploration reached the trench, ocean science was riding a fever of excitement. The landscape evoked imagery from Jules Verne and his submarine odysseys, especially in 20,000 Leagues Under the Sea. Yet the technology of the era could not unlock every secret of the trench, leaving many mysteries to be resolved by future generations.
Location of the Mariana Trench
To endure at such depths, life must withstand pressures hundreds of times higher than surface conditions. The environment is perpetually dark, and temperatures hover just above freezing. Despite these extreme conditions, a handful of expedition teams have descended to the trench floor, revealing a window into a remarkable and largely alien ecosystem.
1. Four manned expeditions reach the bottom
Before this moment, the trench’s secrets remained hidden. On January 23, 1960, Jacques Piccard and US Navy Lieutenant Donald Walsh descended in a bathyscaphe named Trieste. Built by Piccard’s father, Auguste, the craft carried them to the ocean floor after a five‑hour descent. They stayed about twenty minutes before a three‑hour and fifteen‑minute ascent. The journey yielded glimpses of Architeuthis, the giant squid, and other species indicating a unique deep‑sea ecosystem that challenged prevailing science.
The Trieste bathyscaphe remains a landmark achievement in human exploration of the deep oceans.
This daring mission helped propel later deep‑sea efforts and laid groundwork for contemporary research at extreme depths.
The bold spirit of that era mirrored the adventurous drive that has defined ocean science for decades. Later, filmmaker James Cameron repeated the feat with a solo dive to the trench bottom in the Deepsea Challenger, gathering fresh data and samples. His descent reached just over 10,900 meters and demonstrated that humans can operate in these extremes with the right gear and planning. It is widely celebrated as a milestone in deep‑sea science and exploration.
More recent expeditions include several modern dives. A notable 2019 American mission, Limiting Factor led by Victor Vescovo, reached some of the deepest points, with additional descents through 2021. A Chinese submarine, Fendouzhe, conducted dives in 2021 under the supervision of researchers to collect new samples and images, advancing knowledge of the trench’s life and geology.
2. More meters than Everest
The trench reaches about 10,929 meters in places, with measurements sometimes nearing 11,000 meters. This immense depth means that if Everest were placed beneath the trench, roughly 2,000 meters of water would still cover the mountain’s peak. The depth is astonishing, but the biological richness at the bottom is equally remarkable, with life pushed to survive under great pressure, darkness, and near‑freezing temperatures.
What makes the trench extraordinary is not only its depth but the diversity of life that persists under extreme conditions, where pressure and cold challenge biological limits.
3. Formed through subduction
The Mariana Trench formed from subduction, a process in which one tectonic plate dives beneath another. The heavy oceanic plate sinks, creating a deep trench and often sparking volcanic activity that builds nearby islands. Subduction zones run along coasts like Japan and the Caribbean, shaping underwater topography and triggering seismic events that influence the region’s archipelagoes.
Subduction also explains how underwater trenches relate to broader geological features, including island chains and regional earthquakes.
In some cases, subduction involves interactions between continental and oceanic plates, typically with the oceanic plate descending beneath the continental plate. This dynamic drives intense volcanism and mountain-building processes, seen in ranges such as the Andes and beyond.
4. Challenger, deepest point
The trench’s deepest point is Challenger Deep, located between roughly 10,902 and 10,929 meters below the surface. The name honors HMS Challenger, the ship responsible for part of the 1875 exploration. The enormous pressure at these depths is about 1,095 times the surface pressure, making descent and sampling exceptionally challenging. This region remains one of the least explored areas on Earth due to the technical hurdles of landing and staying on the bottom.
The second‑deepest point, Sirena Deep, lies about 200 kilometers to the east, at depths around 10,809 meters. These two zones illustrate the trench’s vertical complexity and its importance as a frontier for ocean science.
5. A reservoir of life in extreme conditions
The trench hosts life forms adapted to immense pressure, almost no light, and near‑freezing temperatures. Plankton, bioluminescent fish, and giant squid inhabit a world that reads like a science fiction page. Explorers have encountered eels and sponge‑like organisms thriving in a pitch‑dark, frigid ecosystem. The seabed sometimes yields mud rich in diatoms, hinting at biological productivity even at great depths.
Later discoveries revealed xenophiophores, organisms resembling sponges but formed as giant single‑cell structures arranged in complex forms. In 2018, deep‑sea observations documented unusually large gelatinous fish at depths around 8,000 meters, including the Mariana snailfish (Pseudoliparis swirei), a species able to withstand pressures that would crush many other creatures. These findings illustrate the remarkable adaptations found in the trench’s dark depths.
These insights reveal a dynamic deep‑sea ecosystem that challenges assumptions about life in extreme environments and expands understanding of biology at Earth’s ocean limits.
6. National monument
Today, a large portion of the trench is protected as the Mariana Trench Marine National Monument, managed by the United States. The Pacific hosts some of the oldest seabeds on the planet, dating back about 180 million years, a factor shaping the trench’s unique geological and biological context.
7. Pollution hits rock bottom
In 2019, the Five Deeps Expedition, led by Victor Vescovo, descended to the trench’s deepest point and found troubling signs of pollution. A plastic bag and candy wrappers were detected even at these remote depths. The expedition crew highlighted the disappointing reach of human waste, underscoring the need for ongoing global stewardship of the oceans.
Source: Oceanographic research teams and related field reports.