Measuring the oceans – curse or blessing?

Looking at Google Maps, it seems as if our blue planet has been mapped down to the last corner. After all, commercial satellites can provide a resolution of about 30 cm per pixel of the Earth's surface. The images of ocean surfaces are rather coarse, with resolutions usually in the range of about five to eight kilometers per pixel.

However, what lies beneath the water's surface remains largely hidden from satellites, as radar signals cannot penetrate water. And so far, only about 20 percent of the ocean floor has been surveyed using sonar.

Seabed 2030 aims to change that: As a joint project of the United Nations and the private Nippon Foundation, researchers from all over the world want to map the entire ocean floor by the end of the decade.

Unimaginable underwater universe

Seventy-one percent of the Earth's surface is covered by oceans, and the sheer size of the oceans is almost unimaginable for us humans, says Laura Trethewey, author of the book "The Deepest Map." "There's simply no equivalent on land, which is why we so often compare the ocean to the moon or space," the Canadian environmental journalist told DW. However, the surfaces of the moon and Mars are better mapped than the seafloor.

Instead of reaching for the stars and dreaming of new, perfect societies on Mars, we should explore "this alien-looking space right here on Earth," Trethewey believes. While we search the universe for extraterrestrial life, the most fascinating and bizarre creatures live in the completely dark world miles below sea level: transparent ghost fish, anglerfish that carry a glowing lure, and enormous giant squid. If you're looking for aliens, here they really exist.

Sound waves make entire worlds visible

To explore the underwater universe, acoustic sound waves are emitted in a fan-like pattern from ships, submersibles, and submarines in various directions toward the seafloor. The travel time of these signals to the bottom and back is measured individually for each beam, and the depth is calculated from this. The deeper the sound, the deeper the sea.

Multibeam echo sounding provides topographic maps, three-dimensional models, and terrain profiles even at very great depths. "There are entire worlds we don't yet know here on Earth, undiscovered mountains and canyons, animals unknown to science, and simply vast amounts of data and discoveries still waiting for us," says Laura Tretheway.

In light of climate change, scientific research into the seafloor could also provide important information about future developments. "Much of the seafloor was once land. After the last ice age, glaciers melted, releasing water that covered continental shelves the size of South America. So there's another continent down there, another lost Atlantis, that could shed light on how past human societies dealt with rising sea levels," Trethewey says. "Nautical charts tell us a lot about the past and the future and also help us navigate the present."

Ambitious mapping project

Seabed 2030 will likely miss its ambitious goal. The oceans are simply too vast, the necessary ships and sonar equipment are lacking, there have been "delays caused by the COVID pandemic, and the political motivation to achieve this has also diminished," says author Trethewey.

"When the project was launched in 2017, the world was less geopolitically fragmented. We now live in a more unstable time, and governments are more suspicious and less willing to share maps." Technology isn't the problem; it's been around for decades.

Organizers tried in vain to "compensate for any shortcomings through innovations such as drones and crowdsourcing, as well as by recruiting superyachts and cruise ships to map the seabed," Trethewey said.

Military and corporations invest in mapping

Deep-sea exploration is an extreme challenge for both humans and equipment. Due to the harsh conditions at sea, an expedition costs approximately $50,000 per day," says Tretheway. "The majority of the unmapped parts of the ocean are located in deep, international waters, which, according to maritime law, belong to everyone and no one. This means that mapping is often carried out by the military or industries such as fishing, mining, and telecommunications, which are not necessarily willing to share their maps."

Seabed 2030 estimates the cost of its self-imposed goal at three to five billion dollars. This roughly corresponds to the cost of the Mars mission that began in 2020, including the landing of the Perseverance rover on the Red Planet.

Do cards ultimately serve the purpose of exploitation?

However, complete mapping could significantly accelerate the exploitation of the oceans . "When people think of maps, they often think of mining and resource extraction . And they're not wrong. There are currently major efforts to develop the deep sea and open the first commercial mines in international waters," says Laura Trethewey.

The environmental author hopes that the mapping will be used primarily for science and conservation. Just as the international community agreed to the Antarctic Treaty shortly after the complete mapping of Antarctica in the post-war period, which protected the continent for scientific purposes for 60 years.

Money and political will needed

Even strict regulations probably can't protect the deep sea as well as our current ignorance and inaccessibility of the oceans. "Almost two-thirds of the oceans and nearly half of the Earth's surface fall within so-called international waters, meaning no country or person has ownership rights to them. This unclear legal status is the main reason why international waters are largely unmonitored and unregulated, and why it's so difficult to combat crime at sea, be it overfishing, pollution, or drug trafficking," Trethewey explains.

"While a stricter ocean policy would be welcome, perhaps even more important are money and political will," the Canadian author told DW. "The ocean is unimaginably vast, and without money for monitoring and enforcing regulations at sea, more rules are largely meaningless."

Laura Trethewey's book "The Deepest Map" was published in September 2025 by Mare-Verlag under the German title "To the Bottom of the World."