In many ways, we know more about the surface of Mars than about the bottom of Earth’s oceans. Yet understanding the oceans not only reveals new wonders about our own planet, it may help us learn more about other worlds as well.

As an example, consider a discovery that was made 40 years ago today. Scientists were studying the Pacific Ocean near the Galapagos Islands, at a spot where new crust is being formed. They found a structure that was spewing super-heated water from deep below the ocean floor. The structure was surrounded by an astonishing variety of life.

Scientists have since discovered many more of these hydrothermal vents. They form when water seeps into the ocean floor, where it’s heated by molten rock. The water spews back into the ocean, carrying a variety of minerals.

Bacteria live off these minerals — something that had never been seen before. They form the first link in the food chain for their environment.

It’s possible that hydrothermal vents could be found on other worlds, including several moons right here in our own solar system. A vast ocean of liquid water probably lies below the icy crust of Europa, one of the moons of Jupiter, for example. Other oceans may be found on other bodies.

The vents on these worlds would have all the ingredients for life: water, minerals, and energy. So discovering life where it wasn’t expected here on Earth can tell us where to start looking for life on other worlds.

Script by Damond Benningfield