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.