INSTANT EXPERT – DEEP SEA LIFE
The Mariana Trench is the world’s deepest place, 11 kilometres below the ocean surface. There is no light and hardly any oxygen – yet there’s plenty of life to be found even in this extreme environment.
Once thought lifeless, Earth’s deepest places are teeming with life.
We have planted flags on the Moon, sent spacecraft to Mars, and taken samples from asteroids 300 million kilometres away. But there are still places on Earth that humans have never visited. The American National Oceanic and Atmospheric Administration estimates that more than 80% of Earth’s oceans remain unexplored, with the deepest places of all being particular blank spots on the world map. Indeed scientists estimate that a mere 0.0001% of the ocean floor has been explored.
At a depth of 11,034 metres, the Pacific Ocean’s Mariana Trench is the world’s deepest place. Pitch darkness and immense pressure make the Mariana Trench almost impossible to explore. But those very conditions make it a fascinating place to study.
Ocean drilling has revealed that the deep biosphere – as deep underground as we can reach – includes more microorganisms than there are stars in the universe. And if we can understand how life exists under such extreme conditions with neither oxygen nor sunlight, it could assist scientists in predicting whether there might be life on planets which are otherwise considered lifeless.
The Mariana Trench is the deepest sea trench that has been identified. There are 27 known deep-sea trenches in the oceans – defined as 6000 metres and below – and they cover a total area similar to that of Australia. The Mariana Trench originated approximately 180 million years ago from a collision between two of Earth’s biggest tectonic plates – the Philippine Plate and the Pacific Plate. This also makes the ocean floor around the Mariana Trench the oldest on
Earth. Scientists used to believe that life simply could not exist at such extreme depths, but they were wrong. Expeditions to deep-sea zones reveal that life exists in the form of starfish, sea anemones, fungi, bacteria, and other microorganisms. Indeed ocean-floor drilling near the Mariana Trench using remote-controlled robotic vessels reveal that the ground beneath contains not mere evidence of life, but so much of it that scientists now estimate that more than 90% of all the world’s microorganisms exist deep in the ground, under the oceans.
The deepest point of the Mariana Trench, down at 11,034 metres, forms an area known as the Challenger Deep. There the pressure is 1000 times higher than at Earth’s surface, the equivalent of carrying a blue whale on your head. When the film director James Cameron made the first ever solo dive
into the Mariana Trench in 2012 to a depth of 10,898 metres in his Deepsea Challenger vessel, he felt as if he was journeying to another planet. Cameron was only the third person in history to get so deep into the Mariana Trench. The first mission had taken place more than 50 years earlier, in 1960, when Don Walsh of the USA and Jacques Piccard of Switzerland dived the Mariana Trench to reach a depth of 10,911 metres aboard the submarine Trieste.
In 2020, the Mariana Trench was visited by the first woman, in an expedition by American adventurer and businessman Victor Vescovo and former astronaut Kathryn Sullivan, who in 1984 had also become the first woman to undertake a spacewalk. The dive was undertaken in Victor Vescovo’s customised submarine, and the two of them reached a depth of 10,918 metres, which was not enough to beat the existing record set the year before, when Victor Vescovo reached 10,927 metres on his own. During his record dive, Victor Vescovo discovered four new species at the floor of the Mariana Trench, and there will almost certainly be more such finds made in the world’s deepest places. In November 2020, three Chinese scientists dived into the Mariana Trench aboard the submarine Fendouzhe. The first dive reached 10,909 metres, and more dives followed. According to their plan, the vessel will take samples of the ocean floor in an effort to teach us more about life under such extreme conditions – and perhaps reveal how it originated.
FILM DIRECTOR JAMES CAMERON ABOUT HIS SOLO DIVE IN THE MARIANA TRENCH: I felt like I literally, in the space of one day, had gone to another planet and come back.