Subtitles section Play video Print subtitles . There are billions of planets in the Universe that, theoretically, can support life. But so far, we haven't discovered any aliens out there. Maybe the reason is we're just looking in the wrong places. What if alien life isn't anything like the life we know of? There is one thing that your DNA, a diamond and a rubber duck have in common. They're all made of carbon. Carbon is one of the most abundant elements in the Universe. On Earth, it's also the primary building block of all life. Carbon is so special because its atoms can make four bonds with another element, oxygen, and form long chains of atoms, called polymers. But there is another element that can do the same trick. Not only is silicon chemically similar to carbon, it also makes it on the list of the most plentiful chemicals found in the Universe. Potentially, silicon could be a building block of organic alien life. And we might find that life in our own Solar System. A candidate for hosting a silicon-based alien life is hiding among the moons of Saturn. Titan, the biggest of these moons, has an atmosphere that's 95% nitrogen and 5% methane. It has no oxygen, and any water it has is frozen solid, because Titan receives only one percent of the amount of sunlight the Earth does. But silicon-based life-forms wouldn't need any water. Instead, they could use liquid methane as the galactic elixir for their existence. The lack of oxygen would also be essential for such life to emerge. Here's why. When carbon unites with oxygen, or oxidizes, as it does during a fire, it turns into a gas, carbon dioxide. Now, when silicon oxidizes, it becomes silicon dioxide, or silica, which is a solid and not a gas. If Titan had oxygen in its atmosphere, silicon would immediately turn into rock, and no life could possibly begin in that state. But Titan's atmosphere doesn't contain any oxygen, giving silicon-based life a chance. Most likely, if there is silicon-based life out there, it would be in the form of microbes, and not animal-size organisms that you can see with your own eyes. Scientists generally agree that any silicon-based life would need intense heat to survive. So most likely, you'd have to dig deep under the surface of Titan to find it. Because of the extreme cold on Titan's surface, a living being would live somewhere close to the Titan's core, where it's hot. And hey, there are many other planets out there. Some of them might have just the right conditions for non-carbon-based life to thrive. Because silicon doesn't get along with oxygen, the metabolic processes of a silicon-based organism would have to be entirely different from ours. We don't know if it's even possible, just as we don't know if anything strictly silicon-based would have a DNA. But maybe we shouldn't try applying "our" science to alien life we've never encountered and planets we haven't thoroughly explored. Earth's conditions don't really give silicon any chance to form into a life-form. But if, one day, aliens came down to visit us here on Earth, they would probably change everything we know about what living organisms could be made of. But that's a story for another WHAT IF.