Less than 30% of Earth’s ocean floor has been mapped while scientists still have clearer high-resolution data of Mars than most of the seabed covering our own planet
Less than 30% of the world’s ocean floor has been mapped to modern standards, meaning scientists still have a clearer view of the Space, Moon and Mars than of the seabed that covers most of Earth.The global effort known as the Seabed 2030 project has raised mapped coverage from about 6% in 2017 to roughly 28.7% as of early 2026, according to tracking data used by the programme and NOAA. That still leaves more than two thirds of the ocean floor unmeasured in any detailed way.The gap is striking because the oceans cover about 71% of the planet’s surface. On the other hand, robotic orbiters 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 which can capture details down to about 25 centimetres in targeted areas. Global Mars maps also exist at resolutions that allow scientists to study surface structure across almost the entire planet. Earth’s deep oceans, by comparison, remain largely blank and dark in high-resolution terms.
Most of the seabed is still unseen
Much of what is known about the ocean floor comes from ship-based sonar surveys. Older single-beam systems recorded one depth point at a time, leaving large gaps between ship routes. Even modern multibeam sonar, which sends out wide acoustic swaths to map the seabed, only covers narrow strips as vessels move through the water.“Sound propagates efficiently through water,” but mapping still depends on ships physically crossing every 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 seafloor shape using gravity signals, but those models only show large features like ridges and basins. Fine details remain out of reach without direct sonar.
From 6% to 28.7% in eight years
When Seabed 2030 was launched by the Nippon Foundation and GEBCO in 2017, only about 6% of the ocean floor met modern mapping standards.Since then, coordinated international surveys and shared data have pushed that figure upward. By mid-2025, the project reported 27.3% coverage, and by early 2026 it had reached about 28.7%.In one recent year alone, more than four million square kilometres of new seabed data were added, an area roughly the size of the Indian subcontinent.More than 185 organisations across over 40 countries now contribute to the GEBCO global grid. New contributors in 2024 and 2025 included Comoros, Cook Islands, Kenya, Mozambique and Tanzania.Commercial ships, ferries and research vessels are also increasingly feeding sonar data into global databases while carrying out routine voyages. Machine learning tools are being used to speed up processing of sonar returns and fill gaps between survey lines.
Why the ocean is still so hard to map
Unlike Mars, Earth’s ocean floor cannot be photographed from orbit. Light does not travel far in seawater, and even in clear conditions it is absorbed within the upper few hundred metres.Most of the seabed lies around 3,800 metres deep. Mapping it 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 must physically pass over every part of the ocean they map.Remote regions are especially difficult. The Southern Ocean, Arctic waters and deep Pacific trenches are hard to access and sometimes blocked by ice or extreme weather.
What 28.7% actually covers
The mapped portion is not evenly spread. Heavily travelled waters such as the North Atlantic, Mediterranean and coastal zones of wealthy maritime nations are relatively well covered.The remaining 71% is mostly deep ocean, including remote basins and abyssal plains in the South Pacific, Indian Ocean and polar regions.Even where surveys exist, resolution varies. The Seabed 2030 target for deep water is grid cells of about 400 metres. Achieving that consistently is difficult because sonar beams spread as they travel and lose precision at the edges.Shallow coastal waters require even finer mapping and bring additional navigation challenges.
Why mapping matters beyond science
Accurate seabed maps are used in tsunami forecasting. Underwater earthquakes reshape the seafloor and influence how tsunami waves travel. Better maps improve warning models and evacuation planning. The 2004 Indian Ocean tsunami exposed major gaps in seabed data across affected regions.Submarine cables also depend on detailed bathymetry. These cables carry most of the world’s international internet traffic. Their routes must avoid steep slopes, trenches and unstable areas. Repairs after damage require precise maps to locate faults.Climate models rely on seafloor structure to simulate ocean circulation. Ridges, seamounts and basin shapes influence how heat moves through the oceans and affect long-term weather patterns.There is also growing interest in deep-sea mining. Companies and governments are exploring areas rich in metals such as cobalt and nickel. Mapping is needed to understand both resource potential and environmental impact, though large parts of deep-sea ecosystems remain poorly studied.
Data, borders and control
Seabed maps also play a role in territorial claims under international law. Under the United Nations Convention on the Law of the Sea, coastal states can extend their rights beyond 200 nautical miles if they prove the continental shelf continues.That makes bathymetric data important for legal claims over underwater territory.In the Arctic, where melting ice is opening new waters, Russia, Canada, Denmark through Greenland, Norway and the United States have overlapping interests. Each has carried out surveys to support their positions.The same data used for science can also shape national claims over parts of the seabed.
The Mars comparison
The contrast with Mars remains stark. Spacecraft have mapped the entire Martian surface from orbit, producing detailed global datasets.On Earth, less than a third of the ocean floor has been mapped to modern standards.That means humanity still knows more about the surface of another planet than about most of its own seabed.Seabed 2030 continues to push toward full coverage by 2030, but at current rates, complete mapping is likely to take longer. Even so, coverage is increasing year by year, and each new survey reduces the size of the unknown areas that still cover most of Earth’s ocean floor.
