Every so often a scientific discovery occurs that makes your eyes open wide and your jaw drop. The finding proves a theory or solves a mystery. Pieces of puzzle fall into place. A blurry image comes into focus.

Sometimes a discovery reveals something that you never imagined. You begin to think about possibilities that you never knew existed and set off in new directions. After discoveries like these, you never look at the world in quite the same way.

The stunning discovery of hydrothermal vents on the seafloor in 1977 was like that. It answered many questions and generated many more.

Hydrothermal vents revolutionized ideas about where and how life could exist. They raised questions that never entered our minds before. How can so much life thrive at the sunless seafloor? What special features do organisms have to live at hydrothermal vents? Why do different kinds of animals live at different vent sites? What happens to the animals when hydrothermal sites get too hot or too cold? How do animals migrate to other vent sites? What else might be living at the seafloor, or below it—or in environments on other planets that we once thought were too extreme to support life? Hydrothermal vents also changed our understanding of how the earth works. Hidden beneath the ocean was a fundamental, but previously unknown, process that explained many basic questions about our planet.

What happens to the great heat flowing out from inside the earth? Why is the sea salty? Why does the ocean’s chemistry remain the same—even after rivers keep dumping elements from land into the ocean? How are some of Earth’s large ore deposits created?

Hydrothermal vents gave us: