You’ve probably heard that old chestnut about how we’ve mapped the surface of Mars and the Moon better than we’ve mapped our own seafloor. It’s one of those "fun facts" people toss around at parties to sound deep. But honestly? It’s basically true. If you’re asking do we know more about the ocean or space, you have to look at what "knowing" actually means.
Is it about pictures? Is it about physical presence? Or is it about understanding the chemistry of what's actually there?
The reality is that we live on a blue marble where roughly 70 percent of the surface is underwater, yet we’ve spent centuries staring at the stars instead of looking down. Space is empty. That's the big secret. The ocean is crowded, heavy, and actively trying to crush any technology we send into it.
The mapping gap is a bit embarrassing
Let's talk numbers for a second because they’re kinda wild. We have 100 percent of the Moon’s surface mapped at a resolution of about 7 meters. We have Mars mapped at roughly 20 meters. But the ocean floor? Until very recently, we only had about 20 to 25 percent of it mapped to a similar level of detail.
Most of our "knowledge" of the deep ocean actually comes from satellites measuring the bumps on the water's surface. Basically, if there’s a massive mountain on the sea floor, its gravity pulls a bit more water toward it, creating a tiny bulge on the surface. We measure those bulges. It’s indirect. It’s like trying to figure out what’s in a wrapped gift by feeling the shape of the paper through a thick pair of oven mitts.
Compare that to the James Webb Space Telescope (JWST). We are literally looking back in time to the birth of the first galaxies. We can analyze the chemical composition of atmospheres on planets orbiting other stars. Meanwhile, if a giant squid decides to hang out at 8,000 meters down in the Kermadec Trench, we might not find it for another fifty years.
Why the ocean is a nightmare for tech
The big hurdle isn't interest; it's physics. Space is a vacuum. It’s "hard" to get to because of gravity and the lack of air, but once you’re out there, it’s mostly just... empty. Light travels forever. Radio waves move at the speed of light without much trouble.
The ocean is the opposite.
Water absorbs light almost immediately. Once you get past 200 meters—the "sunlight zone"—it starts getting dark. By 1,000 meters, you’re in the midnight zone. It’s pitch black. You can’t use cameras to "see" the ocean floor from a distance. You have to use sonar, which is slow and expensive.
Then there's the pressure. At the bottom of the Mariana Trench, the pressure is about 16,000 pounds per square inch. Imagine having an elephant stand on your thumb. Now imagine that elephant is also wearing a stiletto heel. Most of the materials we use for spacecraft would crumple like a soda can under those conditions. Building a submersible that doesn't implode is arguably a bigger engineering feat than building a rocket.
Dr. Gene Feldman, an oceanographer at NASA (yes, NASA has oceanographers), once pointed out that it’s actually easier to send people into space than to the bottom of the ocean. He’s right. More people have walked on the Moon than have been to the deepest point of our own planet.
But we know "more" about space, right?
Well, sort of. It depends on your definition of "space."
If you mean the visible universe, we know a lot about the where and what of galaxies, but we don't know what 95 percent of the universe is actually made of. Dark matter and dark energy are still massive question marks.
In the ocean, we know what the stuff is. It's water. It's salt. It's fish. But we don't know the who.
Biologists estimate that there could be between 700,000 and one million species in the ocean, and about two-thirds of them haven't been described yet. Every time a deep-sea ROV (Remotely Operated Vehicle) goes down, it almost always finds something new. We’re talking about "Dumbo" octopuses, ghost sharks, and weird gelatinous blobs that look like they belong in a sci-fi movie.
The "Nautical NASA" problem
Funding is the elephant in the room. NASA’s budget is usually measured in the tens of billions. NOAA’s (National Oceanic and Atmospheric Administration) budget for ocean exploration is a tiny fraction of that.
People love the stars. They represent the future. They represent "out there." The ocean represents the dark, the cold, and the things that bite in the night. It's harder to get the public hyped about a new species of sea worm than it is about a possible sign of life on Europa.
Ironically, the search for life in space is what’s driving some of our best ocean tech. Scientists are using Earth’s deep-sea hydrothermal vents as "analogs" for what life might look like on icy moons like Enceladus. We are exploring our own backyard to learn how to explore someone else's.
The turning point: Seabed 2030
Things are actually changing. There’s this massive international project called Seabed 2030. The goal is exactly what it sounds like: have a definitive, high-resolution map of the entire ocean floor by the year 2030.
They’re using crowdsourced data from fishing boats, cargo ships, and private yachts. They’re also deploying autonomous "drone" ships that can stay out at sea for months, pinging the bottom with sonar. When the project started in 2017, only 6 percent of the ocean was mapped. We’re now closing in on 25 percent.
So, who wins the "knowledge" fight?
If we’re talking about sheer volume of data, we probably "know" more about space because our telescopes can scan billions of miles in a heartbeat. We have catalogs of billions of stars.
But if we’re talking about intimacy—about understanding the biological and chemical nuances of a place—the ocean is winning, even if we’re slow at it. We can touch the ocean. We can taste it. We can see how it regulates our climate and produces half of the oxygen we breathe.
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Space is a vast, silent mystery that we’re peering into through a keyhole. The ocean is a loud, vibrating, living neighbor whose house we haven’t finished exploring because we’re afraid of the basement.
Ultimately, the question of do we know more about the ocean or space reveals more about our priorities than our capabilities. We’ve chosen to look up because looking down is physically harder.
What you can do to bridge the gap
If this lack of ocean knowledge bugs you as much as it bugs the scientists, there are ways to actually get involved or stay informed without needing a PhD in marine biology.
- Follow the Nautilus Live feeds. The Ocean Exploration Trust broadcasts live video from their ROVs as they explore the seafloor. It’s literally watching discovery happen in real-time.
- Support Citizen Science. Organizations like the Marine Biological Association or local reef watch programs often need help identifying species in photos or tracking water quality data.
- Track the Seabed 2030 progress. Check out the GEBCO (General Bathymetric Chart of the Oceans) website to see the latest maps as they are released to the public.
- Reduce your footprint. One thing we do know about the ocean is that our plastic and carbon are changing it faster than we can explore it. Knowing it won't matter much if we destroy it before the map is finished.
The next few years are going to be massive for both fields. With the Artemis missions heading back to the Moon and autonomous drones hitting the deep trenches, our maps of both "frontiers" are about to get a lot more crowded.