It's the oldest question on Earth.
Where did we come from?
Some people may thank
a creator from above,
but what if the hand that created
humanity wasn't divine?
What if aliens brought life to Earth?
When you think of aliens,
your imagination might run wild
with movie scenes and X-Files reruns.
But technically,
an alien includes anything not from Earth.
And that broad definition opens up
some intriguing possibilities.
In 2017,
astronomers detected a mysterious chunk
from an exoplanet that
entered our Solar System.
Called Oumuamua,
this interstellar object is made
from nitrogen-ice,
the perfect radiation shield for
an organism that might be hitching a ride.
After all,
if this pancake-shaped rock
can keep its ice formation
while flying through the galaxy,
then maybe life can not only exist
beyond the Solar System
but also travel frozen in space.
But if an object like this
slammed into Earth,
When our Solar System was still forming,
the chunk of rock that would become Earth
floated around completely unprotected
from meteors and asteroids.
If an object like Oumuamua had landed
on Earth during that time,
it could've brought microbes
and other organisms from deep space.
This is called the panspermia theory,
which states that that matter from
surrounding planets or objects from deep space might have brought life to Earth.
Researchers aboard the International Space Station
found that bacteria survived on the panels
outside the station.
Even the extreme temperatures of space
didn't kill the bacteria.
Well, what does that prove?
Well, if a spacecraft left from Mars
with microbial life attached,
those microbes could survive
the trip to Earth.
But let's go back to the early days of our planet.
Almost 4 billion years ago,
Earth went through a bombardment period.
During this time,
powerful meteor showers regularly rocked
the surface of our world.
And several objects the size of Oumuamua,
about 800 m (2,600 ft) long,
crashed into the Earth.
So if there were microbes deep
within those meteors,
they might have been cushioned
from the impact.
And during that chaotic time,
life began springing up all over Earth.
After all, bacteria can thrive
in temperatures as high as 113 °C (235 °F)
or be preserved at -196 °C (-321 °F).
So if those meteors had
contained microbial life,
it would have survived the impact
and possibly planted the seeds of life.
But how could we know if
alien life is already here?
Well, that evidence is harder to find.
We still haven't found life
anywhere other than Earth,
so thinking that life could have come from somewhere else might be a bit of a stretch.
But in a system 400 light-years away,
we have found the elements of life.
Using radio telescope technology,
Danish researchers found glycolaldehyde,
a simple sugar needed to produce ribonucleic acid or RNA.
This is the macromolecule responsible for making proteins and coding genes.
Glycolaldehyde is floating
out there in space,
waiting for a carrier
to bring it to a world like ours.
But maybe it's already here.
Amino acids and sugars,
the building blocks of life,
come in two versions
that mirror each other.
We call this phenomenon chirality.
And we refer to the versions as left and right.
But on Earth,
all life contains left-handed shaped amino acids and right-handed shaped sugars.
And that's unusual,
as scientists creating amino acids
in a lab would make half of them left-handed and half right-handed.
So single shapes in amino acids and sugars could be an evolutionary function.
Or they could be
an extraterrestrial influence.
You know, whether life came to Earth
from outside our Solar System in a rock,
or on the bottom of an alien's foot,
it's hard to ignore this theory when we think about our place in the Universe.
But what if our planet has spread
life in the same way?
What if ancient life escaped Earth?
Well, that's a story for another WHAT IF.