More than 80% of the ocean floor remains unexplored today

Introduction: we know the Moon better than our own ocean floor

A figure that sets the record straight

You might think that in the age of satellites and high definition, the entire planet has already given up all its geographic secrets. Yet according to estimates from NOAA and international programs like Seabed 2030, more than 80% of the planet's seafloor has never been mapped with sufficient precision. In very concrete terms, this figure means humanity today knows the surface of the Moon or Mars, photographed in extremely high resolution by space probes, better than its own ocean floor, located just a few kilometers beneath the surface of the seas that cover most of the globe.

This paradoxical reality upends our usual perception of scientific progress. We marvel easily at high-definition images of Martian craters, all while remaining unaware that much of the relief beneath our own oceans is, literally, a blank spot on the map.

A dizzying comparison

Space agencies have complete topographic maps of Mars, Venus, and the Moon, sometimes with resolutions of just a few meters. By comparison, the average resolution of available bathymetric maps for Earth's seafloor remains, in many regions, well over a kilometer. This gap in scale shows just how much space exploration has long captured more resources, funding, and public attention than the exploration of our own oceans, despite their vital importance to the planet's balance.

This imbalance between celestial exploration and marine exploration is nothing new: it reflects historic budget choices that favored the conquest of space, seen as more prestigious geopolitically, at the expense of a better understanding of our own blue planet. A single flagship planetary mission can absorb, in a few years, a budget that would fund decades of systematic ocean mapping, yet space programs remain far easier to sell politically to the public.

Why the seafloor remains so hard to map

Satellites, limited by the opacity of water

Unlike the lunar or Martian surface, which can be photographed directly from orbit, the ocean floor is covered by kilometers of water that completely block visible light and most of the electromagnetic waves used by Earth-observation satellites. This fundamental opacity of seawater forces scientists to rely on mapping methods entirely different from those used for solid celestial bodies without a dense atmosphere.

Some satellite techniques can indirectly estimate ocean depth by measuring variations in Earth's gravity, which slightly affect the height of the sea surface. But this method offers far lower resolution than a direct survey carried out by a ship equipped with sonar, which considerably limits the precision of maps produced this indirect way. Gravity-based estimates can reveal the rough outline of a large underwater mountain, but they cannot distinguish the fine details that matter most to biologists and geologists studying a specific site.

Multibeam sonar, the star of underwater exploration

The most precise method for mapping the seafloor remains multibeam sonar, carried aboard specialized oceanographic vessels. This technology emits acoustic waves that travel through the water, bounce off the ocean floor, and return to the ship, making it possible to precisely calculate the depth and relief of the seabed along a relatively narrow strip with each pass of the boat.

The problem is that each sonar campaign only covers a limited portion of the ocean at a time, and tens of thousands of additional hours of navigation would be needed to cover the planet's entire seafloor using this method. It's a bit like trying to map an entire continent by walking it on foot, one trail at a time.

The real-world consequences of this knowledge gap

A direct brake on discovering new species

This lack of precise mapping considerably slows the discovery of new marine species. Without detailed knowledge of underwater relief, it is very difficult for marine biologists to effectively target their exploration campaigns toward the areas most likely to host rich biodiversity, such as seamounts or upwelling zones that favor the concentration of marine life.

Many recent scientific expeditions have discovered potentially new species simply because they were exploring, for the first time, areas that had never before been the subject of a detailed bathymetric survey, revealing that the mapping gap and the biological knowledge gap are intimately linked to one another.

A brake on our geological understanding of the planet

Beyond biodiversity, this lack of knowledge about the seafloor also limits our understanding of underwater geological processes, such as the formation of new sections of oceanic crust along mid-ocean ridges, or underwater volcanic activity that remains largely unknown in many regions of the globe. Yet these processes play a fundamental role in the planet's overall dynamics, including in preventing seismic and volcanic hazards in certain densely populated coastal areas. A fault line or an unstable slope that has never been properly surveyed can remain an unknown risk factor for coastal communities living just a short distance away.

Better mapping of the seafloor would also significantly improve tsunami forecasting models, since wave propagation depends directly on the underwater relief the waves travel over, a major public safety issue for many coastal regions around the world.

Seabed 2030, the race against time to fill the void

An ambitious goal set for the end of the decade

Faced with this reality, the international program Seabed 2030 has set itself the mission of mapping the planet's entire ocean floor before the end of the current decade. This collaborative project brings together government agencies, oceanographic research institutes, and private partners from around the world, pooling their data and technology to considerably speed up the pace of global mapping.

The data collected is centralized in the General Bathymetric Chart of the Oceans, managed by GEBCO, which serves as the world reference for ocean depth surveys, freely accessible to researchers and institutions worldwide. That open-access approach has become one of the project's biggest strengths, since it lets universities and smaller research institutes contribute data without needing their own dedicated satellite or survey infrastructure.

Autonomous vehicles that are changing the game

The arrival of autonomous underwater vehicles, capable of navigating and mapping entire areas without constant human intervention, represents a major step forward in speeding up this titanic task. These increasingly sophisticated and affordable devices make it possible to multiply mapping campaigns without requiring the costly deployment of a full oceanographic vessel for every mission.

Despite this significant technological progress, Seabed 2030 experts themselves acknowledge that the goal of complete mapping by the end of the decade remains extremely ambitious, given how considerable the remaining task is relative to the resources currently available worldwide, even accounting for voluntary contributions from the private sector and the many national agencies involved in the project.

What this exploration could still reveal

Landforms and phenomena never yet observed

Every new section of ocean floor mapped in detail represents an opportunity to discover landforms and geological phenomena never before observed by science. Underwater canyons deeper than the Grand Canyon on land, unknown hydrothermal vents, or still-active volcanic seamounts could well be hiding within the 80% of seafloor that still escapes our collective view.

There is something exhilarating about realizing that, in the twenty-first century, our own planet still holds entire territories as mysterious as the surface of a distant exoplanet.

A scientific frontier within reach

Unlike space exploration, which requires extraordinarily expensive technology and years of preparation to reach distant celestial bodies, exploring Earth's seafloor remains, by comparison, a relatively accessible scientific frontier. It does not require leaving Earth's atmosphere, but simply investing massively in ships, sonar, and autonomous vehicles suited to this colossal but achievable task. In principle, the entire job could be finished within a generation, given the right level of sustained political and financial commitment across the countries bordering the world's oceans.

The technologies that could speed up global mapping

Artificial intelligence in service of data processing

Beyond the simple collection of raw sonar data, processing that information is itself a considerable technical challenge. Artificial intelligence algorithms are now being trained to automatically analyze bathymetric surveys, identify significant geological structures, and flag for researchers the most promising areas for future in-depth exploration, considerably speeding up work that used to be done manually by teams of specialized cartographers.

These tools also make it possible to more effectively combine data from varied sources: indirect satellite measurements, multibeam sonar surveys, and historical data sometimes collected over decades by different national navies and oceanographic institutes around the world.

Mobilizing the private sector and citizens

Notably, a growing share of the data used by Seabed 2030 now comes from commercial and private vessels, voluntarily equipped with bathymetric sensors that collect depth data throughout their regular routes, at no significant additional cost to their operators. This participatory approach, sometimes compared to large-scale citizen science, makes it possible to multiply available data sources without requiring funding for new campaigns dedicated exclusively to mapping.

There is a remarkable kind of collective ingenuity in turning every cargo ship crossing the Atlantic into a scientific data collector, at virtually no extra cost to anyone.

Conclusion: an exploration that has barely begun

A call to rethink our scientific priorities

The fact that more than 80% of the ocean floor remains unexplored in 2026 should, according to many scientists, prompt a rebalancing of research funding priorities. While space exploration rightly continues to fascinate the public, exploring our own oceans deserves comparable attention and resources, given how considerable the scientific, ecological, and economic stakes are for humanity's future.

Institutions like NOAA continue to actively advocate for increased investment in these mapping technologies, arguing that every dollar invested in ocean exploration generates scientific and economic returns far exceeding its initial cost.

An invitation to collective curiosity

The next time you hear about a new space mission to Mars or the Moon, remember that beneath the surface of the oceans bordering our own continents lies a territory just as vast and mysterious, patiently waiting for its own explorers. Complete mapping of the seafloor is not merely a technical exercise: it is an invitation to rediscover our own planet in an entirely new light, using means that are ultimately more accessible than those deployed for space exploration.

This rediscovery of the ocean, driven by passionate scientists and institutions like NOAA or Seabed 2030, could well become one of the great collective adventures of the coming decades, much as the space race was for previous generations. It requires neither a rocket nor a spacesuit, only perseverance, adequate funding, and renewed curiosity about what has literally been beneath our feet all along. And unlike a trip to another planet, each of us could one day contribute in some small way to this collective adventure, if only by supporting the institutions carrying out this long-term work, or simply by remembering that the ocean beneath our feet deserves as much wonder as any distant world.

By Maxime Marquette, columnist

Sources

Primary sources

NOAA — Ocean exploration and seafloor mapping — 2026

Seabed 2030 — International program for complete ocean mapping — 2026

NOAA Ocean Exploration — Underwater exploration resources and technology — 2026

Secondary sources

National Geographic France — Environment and ocean exploration — 2026

Futura Sciences — News and features on planetary science — 2026

Sciences et Avenir — Science news — 2026