How deep is your knowledge of the ocean?

“Science & Tech How deep is your knowledge of the ocean? Illustrations by Liz Zonarich/Harvard Staff Sy Boles Harvard Staff Writer April 21, 2026 1 min read If you’ve got thalassophobia, this research-backed quiz is not for you. Oceans cover about 70 percent of Earth’s surface area, but largely remain a mystery to us, particularly the deep sea. They are less mysterious to Jeffrey Marlow, author of “The Dark Frontier: Unlocking the Secrets of the Deep Sea,” who completed postdoctoral research in Harvard’s Girguis Lab and is now an assistant professor of biology at Boston University. Marlow helped us develop this quiz on the geology, chemistry, and biology of one of the strangest parts of the world. Related story: ‘Dark Frontier’ author details life in one of Earth’s harshest environments &&& Step 1 of 11 9% 1. Hydrothermal vents, hotbeds of deep-sea life, regularly reach what temperatures, measured in Fahrenheit? 120 degrees 280 degrees 410 degrees 660 degrees 2. If you could stand at the bottom of the Challenger Deep, the deepest known point of the oceans, the pressure pushing down on your head would be about as heavy as which of the following? A Boeing 747 Four elephants The Empire State Building The Moon 3. Approximately how many microbes make their homes beneath the sediment of the sea floor? 200 billion, about twice the number of stars estimated to be in the Milky Way 6 trillion, about as many miles as there are in a light year 300 octillion — that’s 3 with 29 zeroes after it More than a googol, or 10 to the 100th power 4. In what way do some deep-sea microbes protect us from climate change? They cool the surrounding sea water, lowering ocean temperatures They eat methane, a greenhouse gas that traps heat in the atmosphere They sequester argon, another greenhouse gas They create porous channels in rocks, which trap methane and carbon 5. Alvinella pompejana, also known as Pompeii worms, live in the ashy flanks of deep-sea vents and can withstand temperatures up to 200 degrees Fahrenheit. The worms are covered with microbes that produce globs of slime called deepsane. How have humans repurposed deepsane? Ultrasound gel Protective coating for wiring on spaceships Data center cooling mechanisms Anti-aging skin cream 6. Other seafloor materials have been repurposed for human ends, from anti-cancer drugs to biodiesel processing. How big was the marine biotechnology market estimated to be in 2025? $800 million $1.1 billion $6.4 billion $32.5 billion 7. Deep-sea-dwelling mussels in the Bathymodiolus genus in the Gulf of Mexico live hundreds of meters away from the surface world. But they’re connected to the surface in what surprising way? They only feed around the full moon They exhibit seasonal patterns in spawning They’re diurnal They enjoy jazz 8. In 2002, a genus of worm was discovered in the corpse of a whale that had fallen to the sea floor. The worm was dubbed Osedax, a Latin description of what unusual behavior? Eating bones Eating eyeballs Eating eels that feed on the whale’s meat Swimming in the whale’s veins 9. What is an unusual adaptation of Bathyopsurus nybelini, a deep-sea isopod first documented off the coast of Puerto Rico? It swims upside down and backwards It swims using flat translucent pads like ping-pong paddles It has antennae five times the length of its body It has no eyes All of the above 10. True or false: Life in deep-sea trenches tends to be more diverse near the equator and less diverse near the poles, just like on land. True False 11. Which of the following bodies in the solar system is believed to contain liquid water, one of the key ingredients for life? Venus Charon, one of Pluto’s moons Haumea, a dwarf planet beyond Pluto Europa, one of Jupiter’s moons Δ

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