Scientists say we have only explored a small portion of Earth’s seas and oceans
Less than 30% of the world’s ocean floor has been mapped by modern standards, meaning scientists still have a clearer view of space, the Moon and Mars than the seafloor that covers most of Earth.The global effort known as the Seafloor 2030 Project has raised mapped coverage from about 6% in 2017 to nearly 28.7% as of early 2026, according to tracking data used by the program and the National Oceanic and Atmospheric Administration (NOAA). This still leaves more than two-thirds of the ocean floor unmeasurable in any detailed way.This gap is striking because oceans cover about 71% of the planet’s surface. Robotic orbiters, on the other hand, have mapped the entire surface of Mars from space, including features small enough to track sand dunes over time.NASA’s Mars Reconnaissance Orbiter carries the HiRISE camera, a high-powered device that can capture details up to about 25 cm in target areas. There are also global maps of Mars with a resolution that allows scientists to study surface structure across almost the entire planet. By comparison, Earth’s deep oceans remain largely empty and dark at high resolution.
Most of the sea floor remains invisible
Much of what is known about the ocean floor comes from sonar surveys conducted aboard ships.
Older, single-beam systems recorded one depth point at a time, leaving large gaps between ship approaches. Even modern multibeam sonar, which sends out wide swaths of sound to map the seafloor, covers only narrow strips as ships move through the water.“Sound propagates efficiently through the water,” but mapping still relies on ships actually crossing each area. At current speeds and coverage widths, completing full, high-resolution mapping of the oceans would require enormous ship time, fuel, and years of research.Satellites can estimate the shape of the seafloor using gravity signals, but these models only show large features such as ridges and troughs. Fine details remain elusive without live sonar.
And from 6% to 28.7% within eight years
When the Nippon Foundation and GEBCO launched the Seabed 2030 project in 2017, only about 6% of the ocean floor met modern mapping standards.Since then, coordinated international surveys and joint data have raised this figure. By mid-2025, the project achieved a coverage rate of 27.3%, and by early 2026 it had reached about 28.7%.In just one year, more than four million square kilometers of new seafloor data have been added, an area roughly the size of the Indian subcontinent.More than 185 organizations in more than 40 countries now contribute to the global GEBCO network. New contributors in 2024 and 2025 include Comoros, the Cook Islands, Kenya, Mozambique and Tanzania.Commercial ships, ferries and research vessels are also increasingly entering sonar data into global databases while on routine voyages.
Machine learning tools are used to speed up the processing of sonar results and fill in gaps between scan lines.
Why is it still difficult to map the oceans?
Unlike Mars, the ocean floor on Earth cannot be imaged from orbit. Light does not travel far in seawater, and even in clear conditions, it is absorbed in the upper few hundred metres.Most of the seafloor lies at a depth of about 3,800 metres. Mapping them requires sound, not light, and ships, not satellites.Survey vessels are expensive to operate, often costing tens of thousands of dollars per day.
They also move slowly and have to literally pass over every part of the ocean you’re drawing.Remote areas are especially difficult. The Southern Ocean, Arctic waters and deep Pacific trenches are difficult to access and sometimes blocked by ice or severe weather.
What it actually covers is 28.7%
The designated portion is not evenly spread. Heavily traveled waters such as the North Atlantic Ocean, the Mediterranean Sea, and the coastal areas of rich maritime nations are relatively well covered.The remaining 71% is mostly located in the deep ocean, including remote basins and abyssal plains in the South Pacific, Indian Ocean, and polar regions.Even when surveys exist, accuracy varies. The 2030 deepwater seafloor target is grid cells about 400 meters long. This is difficult to achieve consistently because sonar beams scatter as they travel and lose accuracy at the edges.Shallow coastal waters require more accurate mapping and bring additional navigational challenges.
Why mapping is important beyond science
Accurate maps of the sea floor are used to predict tsunamis. Underwater earthquakes reshape the sea floor and affect how tsunami waves travel. Better maps improve warning models and evacuation planning. The 2004 Indian Ocean tsunami revealed large gaps in seafloor data across affected areas.Submarine cables also rely on detailed bathymetry measurements. These cables carry most of the world’s international Internet traffic.
Its roads must avoid steep slopes, ditches and unstable areas. Post-damage repairs require accurate mapping to identify faults.Climate models rely on seafloor structure to simulate ocean circulation. Ridges, seamounts, and basin shapes influence how heat is transported across the oceans and affect long-term weather patterns.There is also a growing interest in deep-sea mining. Companies and governments are exploring areas rich in minerals such as cobalt and nickel.
Mapping is needed to understand resource potential and environmental impact, although large parts of deep-sea ecosystems remain poorly studied.
Data, boundaries and control
Seabed maps also play a role in territorial claims under international law. Under UNCLOS, coastal states can extend their rights beyond 200 nautical miles if they demonstrate the persistence of the continental shelf.This makes bathymetric data important for legal claims regarding underwater lands.In the Arctic, where melting ice opens up new waters, Russia, Canada, Denmark via Greenland and Norway, and the United States have overlapping interests. Each has conducted surveys to support their positions.The same data used for scientific purposes can also shape national claims over parts of the seafloor.
Mars comparison
The contrast with Mars remains stark. Spacecraft have mapped the entire surface of Mars from orbit, producing detailed global data sets.On Earth, less than a third of the ocean floor is mapped by modern standards.This means that humanity still knows more about the surface of another planet than it does about most of its own seabed.Seafloor 2030 continues the push towards full coverage by 2030, but at current rates, full mapping is likely to take longer. However, coverage is increasing year by year, and each new survey reduces the size of the unknown areas that still cover most of the Earth’s ocean floor.
