- [Narrator] Scientists might've just discovered
signs of life on Venus.
- It feels game-changing.
- It is so unexpected,
but I never thought in my life
that it would be something
we should either look for,
or that we would find in Venus.
- [Narrator] Venus is about the size of Earth,
but blanketed by a thick atmosphere.
The surface reaches more than 850 degrees,
hot enough to melt lead,
and the atmosphere is laced with sulfuric acid.
- [Announcer 1] Zero, and liftoff!
- [Clara] Venus used to be
the popular planet to look for life.
Numerous spacecraft - like Magellan -
have flown to the planet, but not many have landed.
- And then, yes, we did send a few probes
that quite traumatically melted on the way down,
and that put us off.
I get it, I would've not continued to try.
The surface of Venus remains absolutely abominable for life.
- It's so hot there, so we wouldn't survive at all.
The sulfuric acid droplets,
they are deathly to any life form.
If you put any kind of life into concentrated sulfuric acid,
it'll just dissolve.
Even though Venus' surface is way too hot
for any kind of life.
There's this Goldilocks zone in the atmosphere
that is not too hot, not too cold,
but just right for life.
- And that's exactly where we found phosphine.
- [Narrator] Phosphine,
the little molecule that might change
how we understand life in the universe.
- Phosphine is known for just being
a really terrible, deadly molecule.
It was used as a chemical warfare agent
in the first world war,
and sadly more recently, by ISIS,
all of which because it's a really effective killer.
- [Narrator] Phosphine is such a good killer of us
because it reacts so easily
with the oxygen that our bodies need to survive.
But for life forms that don't require oxygen,
phosphine isn't toxic, and some organisms
actually produce it.
- Phosphine is associated with microbial life.
It's found in oxygen-free environments,
such as wetlands and swamps and sludges.
It's associated with feces,
so we know for sure that phosphine is associated
with life here on Earth.
- So, a lot of my work was going,
"Oh, if this life on Earth produces phosphine,
could other non-oxygen loving alien life produce it, too?"
My original work had said,
if you find phosphine on any terrestrial planet,
it can only mean life.
And that wasn't an outrageous claim until recently.
- [Narrator] Then in late 2018,
Clara got a strange email.
- It was only when Jane Greaves contacted me
about a year and a half ago saying,
"Clara, you're the phosphine expert.
I think I found phosphine on Venus.
Is that weird?
'Cause I think it's weird."
Then I did freak out because it is very weird.
- [Narrator] Using the James Clerk Maxwell Telescope
in Hawaii, astronomer Jane Greaves
detected a hint of phosphine in Venus' atmosphere
- And she found a signal, phosphine,
a somewhat weak signal.
But it was enough to propose to use the more powerful ALMA,
Atacama Large Millimeter Array telescope
that is in the high deserts of Chile.
And observed Venus again,
and again found phosphine,
this time a much stronger signal.
- And then we were sure the signal was real.
So, we spent the rest
of the year and a half that followed
showing that phosphine
was the most plausible explanation for that signal,
and that if it is indeed phosphine,
life, as strangely as that sounds,
is the most plausible explanation for the phosphine.
- [Narrator] The team used computer models
of Venus' atmosphere and geology
to try to create phosphine without life.
They failed.
- And it's still very, very mysterious.
There could be two different explanations,
both of which are equally, in my mind, preposterous.
One is that there is some unknown chemistry,
or, phosphine might be produced
by some kind of life in Venus' clouds.
- So far, our technique has been
proving all the things that it isn't,
and we've exhausted everything we've got.
With our knowledge of Venus and phosphine
and chemistry and geology
and planetary dynamics, we cannot make phosphine
in any non-biological way
that could justify the detection we got on Venus.
But I'm sure plenty of people will now chip in
with their own expertise,
and I can't wait to see what they come up with.
- Well, this is the first step of a very long journey.
All we can say is, we're confident,
we have a robust detection
of phosphine gas in Venus' atmosphere.
And the rest is really just future research.
- [Narrator] Some scientists are still skeptical
that phosphine on Venus could only be created by life.
- If it is indeed phosphine, umambiguously so,
how do we prove it is life?
And that is not trivial.
I'm extremely excited that we did this on Venus next door
where we actually can go and check.
So, when we get to that point, let's go look.
- [Sara] We hope we can send a mission,
a space mission to Venus,
look for complex molecules that would be indicative of life,
and maybe somehow even look for life itself.
- [Narrator] And if we found it?
- Could be game changing for everyone.
Not just because it would mean
that there's life next door,
which in itself, I think, is a big enough deal,
It's very implausible
that life can originate in both a planet like Earth
and a planet like Venus,
which are so different in so many ways.
And it not be something that can also originate
in a variety of other planets.
And so, life might not just be next door,
it might just be extremely common and inevitable,
which means that there's thousands and thousands
of possibilities for life in the galactic neighborhood
just waiting to be discovered.
So yes, pretty big deal.
(soft music)