I’m speeding through the dark. Silence surrounds me. A numbing cold seeps in through the metal walls of my vehicle. Outside my window, spots glow in the dark like tiny stars.


It may sound like I’m in a spaceship zooming through space. That would make sense because I’m an astrobiologist. Instead, I am in a sub, diving to one of the deepest places in the ocean. What I learn here may help me answer one of the biggest mysteries in our universe. Is there life beyond Earth?


Under the Sea My quest starts with looking for life in a pretty strange place here on Earth. T e sub is now 3.2 km below the ocean’s surface. Its spotlight cuts through the inky water. I see rocks, the sandy seafloor, and not much else. T en a fish swims by. A squid appears out of the darkness. A crab crawls across the sand. T ese sea creatures are like a trail. T ey’re


leading me to a chimney of rocks teeming with life. Toxic fluid bubbles out of this chimney like black smoke. It’s so hot that if the sub gets too close, it will melt. Yet I see millions of blind shrimp floating over the rocks. Tubeworms wave in the bubbling water. Furry mats of bacteria grow on the rocks. It looks like an alien world. It’s dark. T e


water is toxic. Freezing cold and boiling water exist side by side. Yet there’s life here. T is is exactly what I’ve come to see. T ese


organisms can teach me where and under what conditions life can exist. T ey also give me hope. T ey show me that life is possible in an extreme and alien environment. So maybe it’s possible on other worlds.


20 NATIONAL GEOGRAPHIC EXTREME EXPLORER


Where to Look Next, I need to figure out where to look for life beyond Earth. Space is vast with lots of planets, moons, and other objects. Yet I have a way to narrow my search. I’m looking for water. T at’s because life as


we know it needs liquid water. Here’s why. At its most basic, life is a series of chemical


reactions. For example, a chemical reaction breaks down the sugar in food that’s needed for energy. Another chemical reaction builds proteins that, in turn, build an organism’s body. T ese chemical reactions take place in water. Without it, they can’t occur, and life can’t exist.


Signs of Water Using telescopes, space probes, and rovers, we’ve searched our solar system for water. We’ve found plenty of signs of it. T e problem is that most of this water isn’t liquid. It’s either frozen or it evaporated long ago. For instance, a comet zooming through


space is little more than a giant snowball filled with rocks and dirt. Since the water is frozen, life can’t survive on a comet. T e geology of Mars tells us that rivers and


streams once flowed there. Data collected by the rover Curiosity show that a giant lake once held drinkable water. Now, though, we think its water has either evaporated or is ice. Mars is a frozen, dry, and seemingly lifeless planet.


Fun Fact: Comets smashing into Earth long ago might have brought some of the water you use today.


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