In 7.5 billion years,
the Sun will expand and engulf our planet,
destroying all life as we know it.
Of course, a mass extinction on Earth
could happen much sooner than that.
It might even be our fault.
Sooner or later,
humans might have to leave Earth
to find a new home.
But while that might sound scary,
not to mention impossible,
"What?"
Some say it's already been done,
millions of years ago
by organisms much smaller than us,
and not nearly as smart.
Imagine that millions of years ago,
a comet sailed through
the outer atmosphere of Earth.
The comet flew high enough
to avoid burning up in the atmosphere,
but just low enough to pick up
some extremely determined microbes.
The stowaway microbes
embedded themselves
deep within the pores of the speeding comet,
sheltering themselves
from the radiation of deep space.
Eons later,
the comet crashed into a planet
in another solar system.
And the surviving microbes
began to grow in their new home.
According to two astrophysicists
at Harvard University,
this might actually have happened.
But if Earthly microbes did succeed
in trading our planet for a new one,
does that mean that
we could one day do the same?
Microbes are small in size, but
huge in numbers.
And while we have yet to discover
99.999% of them,
the microbes we do know
are vital to our survival.
like algae and cyanobacteria.
And before the evolution of plants,
microbes were the only
oxygen producers on Earth.
So, with that in mind, and
assuming humans would continue
to rely on oxygen to survive,
we might actually need microbes in space
to support our lives on other planets.
If the
"Earthly microbes hitchhiking on a comet millions of years ago"
theory is correct,
then there could be another planet out there
with a habitat that's similar to ours on Earth.
Unfortunately, this "alternate Earth"
would be in another solar system.
And humans have only traveled
as far as the Moon.
The best way to test this theory
would be to send microbes to Mars,
or other nearby "new Earth" candidates,
with the hope that they'd be able to
foster an atmosphere we could live in.
If the microbes we sent from Earth
succeeded in creating an atmosphere like ours
and laying the foundations of a food chain,
we'd have a much better chance of
building a new future for ourselves.
Unfortunately, it's hard to predict
how microorganisms will respond
to being in space.
In some cases,
bacteria can become less harmful,
but in other cases,
they can grow faster
and become much more dangerous.
We don't know how our microbes
could affect any existing eco-systems
on other planets.
They could become an invasive species
that would drive the native life on other planets
to the brink of extinction.
And it's hard to say how
the microbes we sent
would evolve on a new planet.
Sure, we might get some new plants
on a new planet,
but what kinds of plants?
There's also the fear that
if microbes can successfully
planet-hop through space,
then Earth is equally at risk
of being hurt by them.
If alien microbes infected Earth,
it could lead to the development
of new diseases that we couldn't cure,
And without a cure to some unknown,
untreatable alien epidemic
that might suddenly appear on our planet,
we might be forced to leave
our home world after all!
But before you start
aggressively searching for a place to buy
NASA-approved space suits,
you should know that we're far from
having a fully-developed theory
on space-traveling microbes.
After all, we're still learning things
about the biology of our atmosphere,
which makes understanding
how it might've been
hundreds of millions of years ago
even more challenging.
We also don't know just how long
even the most dedicated microbes
could survive.
We know that tardigrades, for example,
can live for decades,
and they're able to survive
the harsh environment of space.
But can tardigrades or anything else
live long enough to make it
to an entirely different solar system?
That remains to be seen.
Or, maybe not.
We don't know exactly when humans
might actually have to leave Earth,
but what if we knew
the exact time Earth was going die?
Well, that's a story for another WHAT IF.