Dear Dakota,

When I think about exploring the ocean, I think about the discovery of giant tube worms. They live in super- hot, mineral-rich water deep in the ocean. They don’t do normal things like eat or poop—but they can live for 300 years or longer. Scientists were shocked when they found them—and there’s probably much more to find.

The worms are long, white tubes with a dark red plume coming out of the end.
These are tube worms that live by underwater volcanoes near the Galapagos Islands. The feathery red part is like a gill. It’s filled with blood. It absorbs chemicals from the water and the volcano vent. Image: NOAA

I talked about ocean exploration with my friend Gretchen Rollwagen-Bollens. She’s a biological oceanographer and plankton ecologist at Washington State University.

She told me that you’re right that we’ve only explored about 5% of the ocean. But it isn’t because we stopped trying. The ocean is just massive.

The ocean contains more than 321 million cubic miles of water. To imagine that, think of something that’s about a mile away from you. You might need to use a map app. Or ask a grownup for a landmark.

Now picture a giant 3D cube that same distance on each side. It’s 1 mile long, 1 mile wide and 1 mile deep. You would need 321 million of those to equal the ocean. Or think of a 1-gallon milk jug. All the water in the ocean would fill about 325 quintillion jugs.

When scientists say we haven’t explored much of the ocean, they don’t mean just the bottom of the ocean. They mean all that water between the bottom and the surface, too. That’s called the water column. It’s the biggest habitat on the planet.

Rollwagen-Bollens told me that exploring every bit of the water column would be tough. There aren’t really landmarks there. It all pretty much looks like water. Plus, once you get deeper than the sun can reach, it’s completely dark.

The water column is divided into zones. Each zone is different in terms of temperature, amount of light and oxygen, and what lives there. Image: Barbara Ambrose/NOAA

“Visiting every place in the ocean wouldn’t help us learn much,” Rollwagen-Bollens said. “The organisms and features of the deep ocean are distributed broadly. So, it makes more sense to be targeted.”

That’s why scientists explore the ocean using sonar from boats or satellites in space. They send sound waves into the ocean to make a picture of what’s underwater. When they see something interesting, they can send a remote-controlled vehicle. Or they can climb inside a submersible like the Alvin to visit in person.

Those vehicles have cameras and robotic arms for taking measurements and samples. Scientists can even take water samples and use the little bits of environmental DNA in there to figure out what living things have been in that water.

Even though we’ve visited only about 5% of the ocean, we know a lot about the ocean floor. Scientists have used satellite data to roughly map the whole thing. They’ve also made detailed maps of about 26% of the ocean floor. That’s done using high-tech gear mounted on ships—like multibeam sonar. They plan to map the entire ocean floor in detail by 2030.

That will help us understand what life is like on the ocean floor—and in the water column, too. Scientists think there could be a million species in the ocean. But we’ve probably only met about one-third of them so far.

That’s a lot of species we don’t know yet. By choosing the best places to explore, I’m sure we’ll worm our way into meeting some of them.


Dr. Universe