Sarah Rugheimer The search for microscopic aliens TED Fellows
[SHAPE YOUR FUTURE]
I want to find aliens.
Finding life on another planet
is not just going to be a little hard,
it’s going to be very hard.
But for the first time in human history,
we have a chance to detect
signs of life on another planet.
Or maybe we’ve already
detected it on Venus.
Or maybe not.
There are still two big hurdles
when it comes to confirming life
on another world.
The first is building a telescope
big enough to do this,
and the second is interpreting
what we will find.
When we think of extraterrestrial life,
we tend to think of aliens like
funny little green men,
not aliens as single-celled microbes.
But it’s actually detecting signs
of microbial life on another planet
that I’m most optimistic about,
and what I focus my research on.
I model how a star’s high-energy radiation
can make gases from microbes
harder or easier to see
with future telescopes.
Microbes have dominated our planet’s
biosphere for most of Earth’s history.
They’ve been emitting gases
that can be seen in our atmosphere –
even light years away –
for billions of years.
Now, if an alien astronomer
were looking at Earth,
they would probably detect gases
like oxygen, methane and nitrous oxide
before detecting signs of us.
Even with an active
biosphere like Earth’s,
most of the gases that indicate life
are coming from single-celled microbes,
not from animals.
This is what we’ll try to do
in the next decade of astronomy –
try to find signs of microbial life
on planets orbiting other stars.
But the technology to detect
the atmosphere
of a planet the size of Earth
around another sun
is incredibly difficult.
It’s like trying to determine the size
of a firefly in front of a spotlight
while looking from another continent.
What’s amazing is that
with telescopes in the 2020s,
we’re overcoming
this technological barrier.
The second issue defining alien life
will be to interpret what these
biosignature gases actually mean.
Twenty-one percent of our
atmosphere is oxygen,
and nearly all of that oxygen
comes from life.
So here’s the tricky question:
Would detecting oxygen
on another planet mean life?
No, not necessarily,
because we know of ways
to get oxygen without biology.
I try to understand a planet’s geology
and its star’s radiation
so that we can better identify
a true life signal.
And this is what makes the preliminary
detection on Venus of phosphine,
a potential biosignature gas,
so compelling but also so confusing.
Venus is not where
we expected to find life.
It is a hellish world,
with a surface temperature
of nearly 900 degrees Fahrenheit.
Could life be floating in the more
temperate upper atmosphere?
But then how would such life
eat and reproduce?
This discovery will have to be vetted
over the coming decade.
First, we must verify the detection
of phosphine itself,
and then later, we would have to confirm
that this gas is coming from life
and not from some unexpected
geological or photochemical process.
If true, this would be one of the most
profound discoveries of our generation.
If it turns out that we were fooled,
that we mistook this gas for biology
when it’s from some other process,
we will have a sobering lesson to apply
to planets orbiting distant stars.
Venus is close – literally,
our next-door neighbor –
and yet we still have trouble
understanding it.
The planets we’re finding
orbiting other stars
are weird and unexpected.
Some have the density of cotton candy,
and others rain molten iron.
And most stars are different from our sun,
with high-energy flares
that can make it difficult for life.
So the more we’re looking at
different biosignature gases,
the more we realize
that there’s no single gas
that’s enough to understand a planet
and to claim alien life.
It is just really difficult
to distinguish life from nonlife
from light years away.
And here’s where the ambiguity lies.
How will we know if a clue
is a sign of life or is not?
Well, first, we’ll need
to understand as much as we can
about a planet’s geology
and the star it orbits.
We’ll learn vital lessons
by exploring our own solar system
in places such as Venus and Mars.
We’re getting closer to answering
one of humanity’s biggest questions:
Are we alone in the universe?
Any claim will be hotly debated.
So basically, I’m stretched
between two desires.
I want to find alien life, but likely
will not have a clear answer.
And that’s OK; science is nuanced
and self-correcting.
It’s what I love about it.
Science is about balancing this duality
of skepticism and of hope.
We won’t be able to teleport
ourselves to another planet
and take pictures of alien
kangaroos jumping around.
And without an intelligent
“Hello, Earthlings!” signal,
we might still feel lonely,
even if we find out
we’re not alone in the universe.
Despite these challenges,
I’m super excited about alien microbes
and what they could teach us.
Even if we find just one
other sign of life,
then likely the universe
is teeming with it,
from single-celled to complex.
If we search for decades and find nothing,
then that is equally humbling.
But we must try.
We must do this search even when it means
sitting with uncertainty along the way.
Thank you.