According to NASA, there are better maps of the Moon’s surface than of the seafloor. For decades, researchers have tried to change that. Based on data from the SWOT (Surface Water and Ocean Topography) satellite, a NASA-supported team published one of the most detailed maps of the bottom of the Earth’s ocean.

SWOT Ocean Mapping

An illustration of the SWOT satellite
An illustration of the SWOT satellite; Photo: CNES

The study authors relied on seamounts and abyssal hills because they have more mass than their surroundings and exert a slightly greater gravitational pull, which creates small, measurable bumps in the sea surface below them. These gravitational signals enable the researchers to predict what kind of seafloor produced them.

The SWOT satellite continuously collects data on the Earth’s oceans, covering about 90% of the globe in 21 days. The satellite can accurately detect centimeter-level differences in sea surface height. While the ocean surface looks flat from above, tiny variations of height differences are caused by underwater features such as seamounts, abyssal hills, and continental margins.

David Sandwell, a geophysicist at Scripps Institution of Oceanography, and his team used a year’s worth of SWOT data to focus on seamounts, abyssal hills, and underwater continental margins, where continental crust meets oceanic crust.

Previous ocean surveying satellites have detected massive seamounts roughly over 3,000 feet tall. However, the SWOT satellite can pick up seamounts half that height, which could increase the number of known seamounts from 44,000 to 100,000. The underwater mountains influence deep sea currents, which influence marine ecosystems.

Why Seafloor Mapping Matters

According to NASA, seafloor mapping is crucial for underwater activities such as navigation and laying underwater communications cables. “Seafloor mapping is key in both established and emerging economic opportunities, including rare-mineral seabed mining, optimizing shipping routes, hazard detection, and seabed warfare operations,” said Nadya Vinogradova Shiffer, head of physical oceanography programs at NASA.

Accurate seafloor mapping also improves our understanding of deep-sea currents and tides, which affect life in the abyss and geologic processes such as plate tectonics.

NASA says mapping the ocean floor is not SWOT’s only mission. It measures the height of all water on the Earth’s surface, including the ocean, lakes, reservoirs, and rivers. Researchers can use the height differences to create a type of topographic map of the surface of fresh and seawater. Then, the data can be used to analyze changes in sea ice or how floods progress down a river.

“The SWOT satellite was a huge jump in our ability to map the seafloor,” said Sandwell.