We thought we knew our solar system.
Turns out we were wrong.
Groundbreaking observations suggest
an unseen ninth planet
may be out there on the fringes of our solar system,
and it could be huge...
5,000 times more massive than Pluto
and 10 times the mass of earth.
We don't get a lot of revolutions in astronomy.
And here we are on the cusp of a discovery like this.
It's crazy to think that,
as much as we've looked into the universe,
that there's this ninth planet out there that we've never seen.
If Planet 9 really is out there,
what will it look like?
Is it a rocky super-earth,
an icy mega-Pluto,
or a gassy mini-Neptune?
Is Planet 9 an alien world stolen from another star?
And could it provide an unlikely home for life
100 billion miles from the sun?
Have you ever dreamed about traveling out of this world?
My name is Mike Massimino,
and I turned that fantasy into a reality
when I space-walked to repair the Hubble space telescope.
Great job, Mike.
Now as we expand our knowledge of our solar system
from Mercury to the cosmic unknowns,
I want to take you on a personal journey to...
Captions by vitac... www.Vitac.Com
captions paid for by discovery communications
welcome to "the planets."
I'm Mike Massimino.
What fascinates me about our solar system
is that everything seems to serve a purpose.
There is a balance, an order out there in deep space.
But what if there is a piece of our solar system
that is making it all tick and we don't know about it yet?
Could there be another planet out there past Pluto?
Researchers now believe there could be one
on the edge of our solar system
100 billion miles from the sun.
Take a look at the night sky.
The stars appear fixed.
But look for longer,
and you'll see a handful of the points move.
These slow-moving points of light are the planets,
the giant chunks of rock or gas
that orbit our home star, the sun.
We thought there were eight. We were wrong.
You know, we think we understand something
as simple as our solar system.
We've found all the planets.
And, right in front of us, we missed something big.
2014.
A group of astronomers are studying the Kuiper belt,
a vast band of icy asteroids
that sits way, way outside the orbit of Neptune.
Most of these objects move in a neat, circular formation
around the sun.
But the astronomers are puzzled by a small group
that appears to break the rules,
swinging far outside the main belt
on wild, extended orbits.
Something sitting far outside the Kuiper belt
seems to be pulling these asteroids out of line,
something the size of a giant planet.
Caltech astronomer Mike brown
hears about the weird observations
and is determined to prove the planet theory wrong.
When we saw these alignments of all
these objects out there, we thought,
"ugh, everybody's gonna say there's a planet.
We have to very strongly prove there's not a planet."
Because, of course, we all know
there's not another planet out there. That's ridiculous.
Mike asks his colleague, Konstantin Batygin,
to run a computer simulation
to see what effect a ninth planet
should have on the Kuiper belt.
Stunningly, the simulation predicts
elongated orbits identical to the ones already observed.
But the simulation also spits out a surprise.
There should be a second set of rogue orbits
that are perpendicular to the first set.
If Mike can locate these weird predicted objects
inside the Kuiper belt,
Planet 9 is almost certainly real.
I took these simulation results to Mike's office
just a couple doors down from my office,
and I said, "look." You know, "we've got a huge problem."
He said, "no!"
There's an object called 2012 dr30
"which has an orbit just like the one you're predicting."
Mike's asteroid fits the prediction perfectly.
He searches the records for more and finds another four
that seem to be in the right area.
But just how closely will they fit the prediction?
I remember sitting back and thinking,
"okay, we're going to, right now, plot the data,
the real observational data on top of the model."
And Mike said, "if these two match up,
my jaw is just gonna drop to the floor."
The theory says they should be right here and right here.
And I did the calculations very quickly
to see where they were and brought them up.
And there they are... One, two, three, four, five,
right on these lines
exactly where we predicted they should be.
The moment we saw this,
we went from cautious
to "holy cow. This really is there."
We have to make sure to tell everybody right away
"because it's actually real."
Mike and Konstantin had unlocked
the solar system's greatest secret.
Planet 9 was almost certainly real.
And it had to be huge,
perhaps 10 times the mass of earth.
We're not talking about something
like our moon or Pluto.
We're talking about something that is literally planet-sized.
And we're seeing its gravitational wake
affecting these other objects.
To prove Planet 9 exists,
astronomers need to see it with their telescopes.
But there's a problem.
Computer simulations only give a broad idea
of where to find it.
And Planet 9 is incredibly faint
and very far away.
It's much, much farther out
than we ever expected to find planets.
It probably spends most of its life,
if it's on an elliptical orbit,
so far away from the sun that we just missed it.
So just how far away is Planet 9?
The only way to truly appreciate its vast orbit
is to build a scale model,
perhaps the biggest working scale model of the solar system
ever attempted.
Planetary scientist Kevin Walsh is here to call the shots.
And he starts with the size of the sun.
So what we've got here, our kickball,
is going to set the scale of our mini-solar system today.
So everything is scaled off of its relative size
compared to the size of the sun.
Kevin quickly paces out the position
of the inner rocky planets.
All four sit within 60 yards of the sun on this scale,
and each planet would appear no bigger than a peppercorn.
To make this a working solar system,
we need to bring on the drones.
Each drone represents a different planet.
And the orbital speeds have been scaled
so one earth year takes just 30 seconds.
Already, it's clear how tightly bunched these inner planets are,
and how the closest planets
orbit faster than those farther out.
Far beyond the tightly packed rocky planets
lies the first of the gas giant planets, Jupiter,
just over a football field from the sun on this scale.
Another football-field length lies ahead
on the walk to Saturn.
As we look back across the lakebed,
I can barely see the drones.
We covered a huge distance.
The trek out to Uranus is bigger still...
Three football fields,
or the length of an aircraft carrier.
It turns out there's a lot of wind in the outer solar system!
So I have to yell.
After Uranus, it's about 200 yards out to Neptune.
Before the discovery of Planet 9,
we thought Neptune was the farthest planet from the sun,
around half a mile on the scale of our model.
But Neptune's distant orbit is nothing
compared to the orbit of Planet 9.
We need to stop measuring in feet,
and we need to start thinking in miles.
We need a car to get out to Planet 9.
Planet 9 swings out on a highly elliptical orbit.
Its closest pass to the sun
is a whopping 19 billion miles.
That's six times wider than the orbit of Neptune.
But, at its farthest point,
Planet 9 is 112 billion miles away.
And, on this scale, that's an incredible 18 miles
from our kickball-sized sun.
So we're here. End of the road.
We've driven about 18 miles
from where we first started setting up the solar system.
But, in the scale of the solar system,
it's over 100 billion miles.
100 billion miles
to get out to the furthest part of Planet 9's orbit.
So, to scale,
and we don't know what Planet 9 would look like,
but it's probably about the size of a B.B.
So, this is the challenge for our astronomers.
How do you see a b.B. From 18 miles away?
This is what we have to do.
It could take years for our telescopes
to see Planet 9.
Until then, scientists can only speculate
on what this mysterious world might be like.
So, what are the options?
Science suggests three possibilities,
and the first is astonishing.
Planet 9 could be made of the same materials as the earth,
but 10 times more massive... A rocky super-earth.
But what would this giant, rocky planet look like
so far from the sun?
A bizarre volcanic planet scarred with fire
somehow emerges from the cold darkness of deep space.
Right now, astronomers are exploring the Kuiper belt,
a vast band of icy asteroids
that sits way outside the orbit of Neptune.
They may have hit the discovery jackpot...
Evidence of another planet nicknamed, for now, Planet 9.
In 2016,
astronomers release astonishing evidence
of a missing ninth planet
on the frozen edges of our solar system,
100 billion miles from the sun.
Until our telescopes find it,
we can only guess what this mysterious Planet 9 is like.
But the first option is perhaps the most surprising.
Planet 9 could be made from rock,
just like the earth,
but 10 times more massive,
a so-called rocky super-earth.
When we looked out into the universe, we realized
that the most common type of planet
in the entire galaxy is something we don't have,
something called a super-earth.
The Kepler space telescope finds alien worlds
by measuring the tiny dip in light
as a planet passes in front of its host star.
Most of the alien solar systems Kepler finds have super-earths.
So how come our star doesn't have one?
If Planet 9 is a rocky super-earth,
what will it look like up close?
Planetary geologist Jani Radebaugh imagines Planet 9
as a dramatic world of fire and ice.
Right now, we're in Iceland.
We're flying over amazing,
beautiful volcanic landscapes of Iceland.
We think this might be the perfect landscape
for thinking about what might be happening on Planet 9
if it's a rocky super-earth.
These black mountains and lava flows
were created by leftover heat
from the earth's formation spilling out onto the surface.
Planet 9, born with so much more insulating rock,
should have even more of this leftover heat trapped inside it.
What we're talking about is a body
that's maybe 10 times the mass of the earth.
I'd expect, because it's so large,
that we should have lots more internal heat.
And so, even though it's far away in the solar system,
it's far away from the sun,
it's still got lots of its own energy.
Touching down on the surface of Planet 9,
you'd find a world as inhospitable
as you could imagine.
Billions of miles from the sun,
the surface is lit by little more
than the twinkle of distant stars
and the red glow of intense geological activity
on the surface.
We can imagine, if we were on
a super rocky earth Planet 9,
we could have a landscape just like this one.
There should be volcanoes erupting all the time.
And the other thing we should see
is lots and lots of ice and snow blanketing the landscape.
This is because the atmosphere is so cold
that parts of it have condensed
and settled back down onto the surface.
You're gonna have volcanoes. You're gonna have canyons.
You're gonna have plate tectonics, mountain-building.
All of these processes are still gonna be going on out there
in what we normally would think of as the frozen, cold,
and dead world of the outer solar system.
The case for a giant, rocky Planet 9 is compelling
because it paints such a vivid picture
of a living volcanic world.
But there's a problem.
If Planet 9 is, in fact, a super-earth,
how did it form and where did it form?
We don't have any other super-earths
in our solar system.
And the ones we see around other stars
are typically really close to their star.
So how did our super-earth end up way out there
at the edges of our solar system?
For Planet 9 to be a rocky super-earth,
it would have formed in the inner solar system
and then migrated out to its current position.
And that's a problem,
because there probably wasn't enough rocky material left over
in the early solar system
to create both the massive Planet 9
as well as Mercury, Venus, earth, and Mars.
It's really hard to imagine
that we could have formed a 10-earth-mass planet here
and still formed the rocky planets that we see today.
Time for a new theory.
What if Planet 9 formed from ice
in the outer solar system?
Calculations tell us it would have to be 10 times
the mass of earth.
And here's the kicker.
An ice world that big
would have an internal ocean of liquid water.
A new world is revealed
where icy geysers shoot through cracks
in the frozen crust.
And deep below it
lies the largest body of liquid water
in the solar system.
Because our solar system already has four rocky planets,
it's not likely that our elusive Planet 9 could be a rocky giant.
So what's the next theory?
Planet 9 could be a ball of ice.
The planets that make up our solar system
seem to follow a pattern.
The four closest to the sun are all made from rock.
The next four are giants made mostly from gas.
Beyond Neptune, gas is replaced
by multiple worlds made from ice.
This is the Kuiper belt,
a frozen realm of water-ice asteroids...
Millions of them.
The Kuiper belt is a region of space
outside of Neptune's orbit that extends out
about 50 times the distance from the earth to the sun.
So it's really far out there.
And this is populated by icy bodies.
These are giant chunks of ice
that have some rock and other things in them.
But they're mostly ice.
Perhaps Planet 9 is made from the same materials,
an overgrown version of the Kuiper belt's
most infamous citizen, Pluto.
Poor Pluto.
Discovered in 1930 by Clyde Tombaugh,
this tiny ice world, smaller than our moon,
was quickly proclaimed the ninth planet.
But in the 1990s, Mike brown and others
discovered a host of icy worlds orbiting out with Pluto.
Pluto was just another Kuiper belt object
and got demoted to dwarf planet,
to the dismay of much of the world.
Everybody loves the idea that... that I killed Pluto,
and now I'm trying to atone for my sins
by replacing it with a new ninth planet.
In fact, even my daughter suggested this
long before we started looking for Planet 9.
She said, you know, "you should find a new planet."
And then you can have found a planet.
And there'll be nine planets again.
"And everybody will like you again."
If Planet 9 is an icy Kuiper belt world,
it'll be the biggest we've ever found.
Pluto, the biggest object
we know out there in the Kuiper belt now,
is less than 1% the mass of the earth,
less than that.
Planet 9, we think, is 10 times the mass of the earth.
So we're dealing with a factor of thousands of times in mass
between the largest Kuiper belt object
that we know now
and the size of Planet 9.
So you're talking about super-mega-ultra-Pluto.
It's really, really big.
And it's hard to know what an ice ball
like that would look like.
It's not crazy to speculate that there could still be activity,
internal geologic activity,
keeping this world from being cold and totally dead.
Peering through the darkness
to a hypothetical mega-Pluto Planet 9,
we discover a giant world of ice.
There's much less rock than a super-earth Planet 9.
But the mass of ice alone creates enough gravity
to generate heat deep in the core, even out here.
The real currency of keeping a planet alive is mass.
Does it have enough mass to keep the interior warm?
Well, something that's 5 to 10 times
the mass of the earth probably would be warm inside.
Up close, the surface explodes with activity.
But these volcanoes spew water ice, not lava.
You'd have these ice volcanoes spewing out jets
of frozen water, of ice raining down on you.
Maybe you'd look out over the landscape
and see hundreds of these erupting.
This dramatic ice vista is a gateway
to a secret world,
a vast, slushy ocean of liquid water
mixed with ice crystals,
perhaps the largest
single body of water in the solar system.
There's gonna be enough internal heat, maybe,
to turn this into a slushy water world.
So it's not quite a terrestrial, rocky planet.
And it's not a Uranus or Neptune.
It's a true mega-ocean world,
but perhaps a very cold one.
Is Planet 9 an icy mega-Pluto?
The problem is scale.
Pluto and the other objects in the Kuiper belt are tiny.
So how could the same building materials
have come together to form a giant?
So, the idea that Planet 9
is simply a really scaled-up Pluto, a mega-Pluto,
has some difficulties.
We just don't think that there was enough mass out there
in the far reaches of the solar system
to all come together to build a planet that large.
When you look at the Kuiper belt,
there are all of these small, icy bodies.
There's nothing very big out there.
And we think that's not a coincidence,
that the disk of dust and gas that formed the planets
had more stuff closer to the sun.
And by the time you got out to where Pluto is,
there wasn't much material to build planets out of,
certainly not a planet
5 to 10 times the mass of the earth.
So, if Planet 9 didn't form
in the icy outer solar system
and didn't form in the rocky inner solar system,
where did it form?
The more likely option,
Planet 9 formed in the gas-rich zone
in the middle of our solar system
that also created Jupiter, Saturn, and Neptune.
A gassy Planet 9 could be similar to Neptune,
but perhaps a little smaller,
a mini-Neptune.
But how would it get so much farther out
than the other gas giants, and what would it look like?
Imagine a weird, translucent world
glowing in the dark like a giant deep-sea creature.
And liftoff!
So we can only predict what this planet might look like.
Scientists believe the most likely possibility
is a mini-Neptune, another gassy giant.
But the cool thing about this gas planet
is that it would light up
like a deep-sea, glow-in-the-dark jellyfish.
Something on the fringes of our solar system
is upsetting orbits and causing a ruckus.
Could it be a planet?
It's incredible to me that we now know
of thousands of other planets
going around other stars in the sky,
but we may have missed a big planet
in our own solar system.
Planet 9, a world we know almost nothing about,
beyond the possibility that it exists.
Science suggests intriguing options.
So, if it's not a rocky, metallic super-earth
and it's not a gigantic, ice-ball mega-Pluto,
what's left?
And the answer is a gas giant.
And that strikes me as being the most likely prospect.
When you think about the mass of Planet 9
and where it is now, my best guess,
it's something like a miniature version of Neptune.
The gas giant planets
are the monsters of our solar system.
Instead of a solid surface, like the earth,
the gas giants have thick, stormy atmospheres
that descend for tens of thousands of miles,
shrouding their small, rocky cores.
Jupiter is the largest gas giant...
Over 300 times the mass of earth.
Moving out from Jupiter,
the gas giants get progressively smaller,
Saturn, then Uranus, and finally Neptune,
around 17 times the mass of earth.
If Planet 9 is a gas giant,
it'll be even smaller, a mini-Neptune.
If Planet 9 is a mini-Neptune, if it's a lot like Neptune,
then it's not really like
a terrestrial planet, like earth.
But it's not really like a gas giant, like Jupiter.
Neptune is this weird, in-between thing
where it's probably got a rocky core.
But it's actually, mostly, what astronomers call ices.
It's got methane in it and water and various other substances
and a very, very, very thick atmosphere on top of that.
Neptune's thick clouds are stained blue
with molecules of methane.
But Planet 9's atmosphere could be transparent.
It's so cold out there,
you're getting almost no extra energy from the sun.
And so then anything heavy in the atmosphere,
any heavier molecule, over time,
would have probably fallen to the surface.
And only the lightest elements, the lightest molecules,
would stay in your atmosphere,
so maybe just almost pure hydrogen or helium.
And you'd have, maybe, a really clear atmosphere.
What would a mini-Neptune look like
that far out from the sun?
The thing I think of are things like jellyfish, right?
That sort of beautiful, translucent look,
where you're looking through to the innards of the organism.
In this case, you might look through
to the innards of the planet in some way.
The atmosphere may be transparent,
but this planet is far from calm.
The interior is lit by the flash of thunderstorms,
and faint lights dance as solar winds from distant stars
stream down the planet's magnetic fields.
Looking into the innards of the planet,
it would look, in some ways, like these gorgeous,
beautiful deep-sea organisms that are bioluminescent.
And we may have the planetary equivalent
of something like out there in the inky blackness of space,
rather than the inky blackness of the deep ocean.
Surprisingly, the possibility of an extra gas giant
in our solar system isn't new.
In 2011, scientists attempted to replicate the formation
of our solar system using supercomputers.
But their models didn't work
unless they added an extra gas giant planet to the mix.
It was really difficult to reproduce
our current solar system.
But one scientist found that,
if you add a fifth large planet
to our solar system,
then that planet will end up
getting ejected from our solar system.
And you'd have the planets that we have today.
Is Planet 9 the missing gas giant
predicted by supercomputers?
The computer models shows it being ejected
by the immense gravity of Jupiter.
But did Planet 9 instead cling on to our solar system
by the tips of its gravitational fingers?
Sometimes, our mathematical models
predict things that we think are impossible.
And then we find them.
And, for a while, we've known that,
if you throw a mini-Neptune into the mix of planets forming,
the models work better.
Maybe we found that key, finally... Planet 9.
We know giant planets can get thrown around.
Observers have even seen ejected planets
floating free in the space between stars.
Did Planet 9 almost suffer the same fate?
It's entirely possible that there could've been
a planet forming bigger than earth,
something like a super-earth, well on its way
to becoming a gas giant
in this wonderful area of the disk,
where it could've drawn in a lot of material
and become a gas giant like Jupiter,
except it got too close to Jupiter.
And, before it could do that,
it was gravitationally flung away
from this wonderful feeding ground
out into the much sparser,
more barren desert of the outer solar system.
Is Planet 9 really a frozen mini-Neptune
banished to the badlands of the outer solar system?
Right now, it's our best bet.
But there is one more option.
Some scientists believe
Planet 9 may not have formed around our sun at all.
Is our most distant planet
an alien world snatched from another star?
Like everyone else in the space world,
I'm on the edge of my seat
wondering if Planet 9 truly does exist.
But forget about what Planet 9 looks like for a second.
Where exactly did it come from?
Researchers now suggest it might have been a case
of solar system high-stakes robbery.
If the mysterious Planet 9 exists,
it's by far the most distant planet
in the solar system,
nearly 20 times farther out than Neptune.
So how did it get there?
Was it made out there from ice,
or was it flung out from the inner solar system
as a rocky super-earth
or, more likely, a mini-Neptune?
The jury's out.
But there is another option.
And it's out of this world.
And it's possible that there is another explanation.
And that is that Planet 9 is an alien visitor
from outer space.
The sun is just one of 200 billion stars
orbiting the supermassive black hole
at the center of the milky way galaxy.
Most of these stars probably have multiple planets.
And scientists now believe that, from time to time,
two stars might pass a little too close for comfort.
The result... planetary theft.
Today, our sun drifts through space alone,
like a yacht in the open ocean.
But that wasn't always the case.
Rewind the clock 4.6 billion years,
and our local star cluster was a much more crowded place,
ideal conditions for Planet 9 to jump ship.
The sun was born in a nursery
with thousands of other stars.
Just like the boats in this harbor,
there are so many boats around, so many neighbors.
It was like that for the young sun.
Stars like the sun are born in stellar nurseries,
vast clouds of gas that collapse
to form tens of thousands of stars,
all tightly packed together.
Astronomers think it's possible
that, inside this cramped, confused playground of stars,
our sun's gravity could've stolen Planet 9
from a passing neighbor.
Imagine this cool scenario.
You've got an alien star.
And around that star forms a planet.
This is Planet 9.
And here comes the sun whizzing by.
The sun gets so close that it steals Planet 9
on its way out into the galaxy.
It sounds like science fiction.
But our sun may already have a criminal record.
There's some evidence that the comets in our solar system
may not have started in our solar system.
We may have stolen comets from other stars.
If that's the case, it's not totally outrageous
to think that a planet that formed around another star
somehow made its way into our solar system
and became part of our family.
But if Planet 9 really did come from another star,
how will we know for sure that it's an alien visitor?
What we'd like to do is essentially
a DNA test on Planet 9,
scoop up some of its surface,
and look for material that we absolutely know
couldn't have formed around our sun,
because we don't see it anywhere else in our solar system.
We may even have to send a probe there
to really get a good look at it
and find out what its chemical composition is,
exactly everything we can find out about its orbit.
And, that way, we might be able to see
if there are any sort of fingerprints,
smoking-gun pieces of evidence
that'll say clearly this formed here
or it formed out there.
Before we can launch a probe to Planet 9,
we first have to find it.
Astronomers like Mike Brown
have made the challenge a little easier,
using math to narrow down the hunt zone.
What we know right now is that Planet 9
is in a swath of the sky that goes about like this.
It's about this big. It goes across like this.
But we think we even know a little bit better.
We've pinpointed, or at least slightly constrained
where it is, to a patch of sky that's about this big.
It's still a lot of sky to look at.
But it's a lot less than having to look at the whole sky.
Mike's patch of sky is close to the constellation of Orion.
He's going to wait until fall,
when Orion is the highest in the sky,
to search for Planet 9
using the Subaru infrared telescope on Hawaii.
The telescope is fine-tuned
to pick out the faint heat signature of distant objects
against the cold backdrop of deep space.
Planet 9 may be frozen.
But it will be warmer than space.
And that tiny difference in temperature
is all this incredible telescope needs.
We want to see two pictures taken
of the same area of the sky a few weeks apart.
The stars don't move.
But you see this one little thing going, "boop, boop, boop,"
as you flash the pictures back and forth.
That's what happens when you have an object
moving around the sun against the background of stars.
That's how Pluto was discovered.
That's how we're gonna find Planet 9 if it exists.
It could take years to find Planet 9.
But when we do spot it,
scientists will be able to analyze its light.
And hidden within that faint glow
could be the chemical signature for rock, ice, or gas.
If they do, Planet 9's identity will finally be revealed.
What lies in store beyond that is a mystery.
But perhaps the most exciting prospect
is Planet 9 could be home to a family of moons.
It's just possible one of these moons
could provide a home for life
100 billion miles from the sun.
A stealthy extra planet
could be lurking in the depths of our solar system.
What's even more exciting
is that large planets usually come with moons.
And moons are where scientists think life
could be supported outside of earth.
So the race is on to find Planet 9 and its moons.
Are we alone in the universe?
For decades, scientists have scoured
our closest planetary neighbor
for signs of extraterrestrial life.
But so far, not a trace has been found.
Is it possible we're targeting the wrong planet?
If Planet 9 is real,
it sits on the icy outer limits of the solar system.
But even here, 100 billion miles from the sun,
it's just possible life could thrive
not on the planet itself,
but deep inside its moons.
Historically, we've always thought of moons
as being these little, insignificant places.
But the incredible thing is they may be
the best places to find life.
In our solar system alone,
there may be far more chances for life on moons of planets
than there are on planets themselves.
Moons excite astrobiologists
because they can sometimes support liquid water,
no matter how far they sit from the sun.
The key is something called tidal heating.
Moons on elliptical orbits get squashed
and squeezed by the gravity of their parent planet.
This generates heat and melts ice
to form underground oceans of liquid water,
the key ingredient for life as we know it.
If Planet 9 is as big as scientists predict,
it could have multiple moons.
And perhaps one of these moons
could have warm, salty oceans
primed for simple life.
So, if you have Planet 9
and it's got icy moons and these icy moons
are on the right kinds of orbits,
the heat could be coming from within, not without.
And so the sun basically doesn't matter.
You could have liquid water below the surface
that's heated from the internal geology.
You could have geysers of water
like what we see coming off of moons
around Saturn and Jupiter.
You could have that all the way out there at Planet 9.
Imagine Planet 9 with a system of giant moons.
The closest moon is heated to melting point
by Planet 9's immense gravity.
There's no life here.
Any water boiled away millions of years ago,
creating a hot, arid ball of rock.
Farther out lies a second giant moon.
This new world is encased in bright, white water ice.
But the crust hides a secret...
A vast ocean of warm liquid water
heated by volcanic vents on the ocean floor.
This hidden world is rich with active organic chemistry,
and it could even support a weird, alien zoo
of pale aquatic creatures.
We associate life with the sun.
That's how we think of life originating on the earth.
But we know you don't need the sun.
We have tube worms at the bottom of the ocean
which live off of hydrothermal vents.
They get all the chemicals and the heat they need
from, basically, the interior of the earth.
This is not out of the question.
You know, decades ago, you'd have been laughed out of a lecture hall
if you'd have said something like that.
But we have learned so much about life
in extreme environments since then
that this is now in the realm of possibility,
talking about life on a planet
beyond Pluto in our own solar system.
Wherever there is energy,
wherever there's heat, there can be life,
even all the way out by Planet 9.
There's good news.
If Planet 9 does have an active watery moon,
we should be able to see it with our telescopes.
The active moons of Jupiter and Saturn
are the brightest in the night sky,
thanks to warm water gushing out from cracks in the surface
and freezing out in bright white layers of fresh ice.
If Planet 9's moons have liquid oceans,
their surfaces should be just as bright.
The race to image Planet 9 and its moons is on.
But what we'll see when those first pictures come back
is anyone's guess.
I have to admit, there's some wonderful tension
that I feel right now when it comes to finding Planet 9.
We have giant telescopes
that are scanning the sky looking for it.
So, any day now, I'm waiting with baited breath.
If and when we do find Planet 9,
we'll never look at our solar system the same way again.
This is tremendously exciting,
because, if it's there, it's already telling us
that there's more to know about our solar system,
that there are more secrets literally under the sun
than we have dreamed of in our philosophy.