99.999% OF EARTH'S DEEP SEAFLOOR YET TO BE OBSERVED

More than 97% of all deep-sea dives have been conducted by just five countries, according to a new study exploring biogeographical biases

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Two-thirds of the earth’s surface consists of the deep ocean — parts of the surface 200 m or more below sea level. It’s thus the world’s largest as well as least explored ecosystem. A new study in Science Advances by U.S. researchers has estimated how much of the deep seafloor humans have observed visually so far, to quantify what remains unseen and geographic biases. Visual imaging is an important way to study deep-sea ecosystems because it yields the context from which biological and geological samples have been extracted and helps calibrate remote-sensing data.