# Is there Life Elsewhere In the Solar System? Are we alone in the universe?
As big as big questions go, it’s one of the biggest we’ve yet to know. The idea that other advanced civilisations
might be out there somewhere, peering up at some of the same stars we do through their
freaky eyes is incredibly intoxicating. But the truth is, finding other intelligent
species remains a distant dream - quite literally. Imagine a million civilisations with
human-level technology living right here in our very own galaxy, The Milky Way. That
sounds like a lot, right? We'd be dodging ETs every time Elon Musk launched a
rocket. But, as is often the case, the sheer enormity of outer space
makes a mockery of human intuition. In reality, if there were a million civilisations
evenly distributed throughout the Milky Way, our nearest neighbours wouldn’t be hanging out just
around the corner, but about 300 light years away. That's a distance so vast we might never have the
technology to blast, warp, or teleport across it. As of today, the furthest man-made object from
Earth is NASA's Voyager 1 probe, which left our home planet in 1977. In the four and a bit
decades since, despite travelling at a fairly nippy 17 kilometres per second, Voyager 1 hasn't
even made it a single 'light day' from earth, let alone a light year. So those alien neighbours
I mentioned, living 300 light years away, yeah, it would take Voyager five and a half million
years to pay them a visit. And that’s just a tiny probe, not a monolithic colony ship
capable of transporting the thousands of people necessary to prevent inbreeding
megadeath during a trip between the stars. What I'm trying to say is, the universe
is colossal, and while it's by no means out of the question that we might one day
*detect* aliens out there among the stars, the chances of us actually crossing
are pretty much nothing - well, not unless they approach us first, and if that
happens we may end up wishing they hadn’t. Luckily, to meet ourselves some aliens we
might not have to venture too far from our home star - because it turns out there's a
decent chance they might already be living among us... Well OK not exactly among us.
More like… just down the road. And no, I’m not talking about the Facebook headquarters. You see, scientists are becoming
increasingly optimistic that alien life might already exist in our solar system,
though admittedly these otherworldly lifeforms are unlikely to be anything other than
simple microorganisms (if there was another advanced civilisation chilling out on
Saturn we'd probably have noticed it by now). Microscopic aliens might sound a little
less exciting than, I dunno, the Borg, but finding a single alien microbe clinging
bravely to the surface of a world other than our own would be one of the single biggest
moments in human history. Not only that - it would fundamentally change our understanding
of the entire universe. Let me explain. At the moment, we essentially have
no idea whatsoever how common life is. Maybe we're entirely alone in the
universe, or we could be just one of quadrillions of different lifeforms living on
hundreds of trillions of different planets. That isn’t hyperbole either -
it genuinely is that wide open. Finding life elsewhere in our
solar system would dramatically and instantaneously change that picture. Because if life evolved independently *twice*
in the very same solar system, it would be an incredibly strong indicator that life is rife. And
that would be an absolute game changer. After all, it's starting to look like planets with habitable
conditions are pretty common - according to a 2020 study, there might be as many as
300 million of them in our galaxy alone. In other words, finding life here
in our own solar system - even simple life - would all but confirm
that we have a *lot* of neighbours. So yeah, it's probably worth having a look. The only question is - where's
the best place to start? ## Venus To the uninformed observer, Venus might not
seem like an obvious place to go looking for aliens. To be honest, even to an informed
observer things don't look all that promising. We're talking about a planet shrouded in
clouds of concentrated sulphuric acid with surface temperatures of about 500 degrees
celsius - that's hot enough to melt lead. Any plucky alien visiting Venus would also be
under a lot of pressure, not from his petulant boss - but the kinds of pressure only found
at 1000 metres below sea level here on earth. In other words, Venus is pretty much the
dictionary definition of uninhabitable - the kind of planet a Sith Lord might build a base on just
to look like a badass in front of his sithy mates. But here's the thing - Venus hasn't
always been a brutal hellscape. Not long ago, our neighbour planet may
have been, well a bit more neighbourly, with a temperate climate and liquid water
on its surface. Even better, according to a 2019 study by NASA, these positively
pleasant conditions probably persisted for upwards of 3 billion years - that's more than
enough time for life to... well, find a way. Of course, given the conditions
found on Venus today, it’s highly unlikely any life lingered for this long. Unless… Back in 2020, British scientists observing
Venus' fiery atmosphere detected something they didn’t expect to detect - traces of a gas called
phosphine. The find stunned the scientific world, and once they came to they realised that on
terrestrial planets like Earth and Venus, phosphine is only created
through biological processes. In other words, if there's phosphine on
Venus, that means there's *life* on Venus. But before you go and hang out your First
Contact bunting, I should probably mention that the whole 'phosphine on Venus' thing is
a little bit controversial, and several recent studies dispute the findings. Still, we can’t yet
refute that life once existed on Venus, and with no fewer than 6 missions due there in the next 10
years or so, who knows - we might just find it. ## Mars If not Venus, maybe Mars is
where we’ll find our first, well, Martians. There's a whole bunch of
evidence supporting the idea that liquid water once flowed on its surface in significant
quantities, and thanks to NASA's Curiosity rover, we also know that organic compounds - examples
of prebiotic chemistry - are found there too. Sadly, like Venus, the Red Planet isn't exactly
a great holiday destination these days. Average surface temperatures hover at around -60 degrees
celsius and the atmosphere is incredibly thin, with surface pressures about 1% of those found
on earth. Mars also lacks a magnetic field, meaning it gets absolutely blasted with
ionising radiation, which is lethal to life. That's the bad news. The *good* news is
that, if life has *ever* existed on Mars, there's a pretty decent chance we'll be able to
find it. The planet isn't tectonically active, meaning the majority of its surface is more
than 3.5 billion years old - in other words, it’s one giant Time Capsule. Theoretically, traces of ancient life lie tantalisingly
tucked away in this big red treasure trove. As I say these words, NASA's Perseverance
Rover is trundling about the Martian surface, patiently bottling up rock samples for
return to Earth in the early 2030s, where they'll be examined by the best labs
ever built by humans. If Mars was ever home to alien life, we have an excellent chance
of proving it within the next decade or so. When we talk about the search for alien life,
we tend to focus our attention on planets. I guess that's understandable - we have pretty
strong confirmation bias (you’re looking at it). But while Mars and Venus may
have been habitable millions, even billions of years in the distant
past, it turns out that some of our solar system's more than 200 moons
may still be habitable *right now*. ## Europa For a long time, the most promising of which was
Jupiter's moon Europa. And while its claim to that title is perhaps flimsier than it used to be -
mostly because of another fascinating moon I’ll tell you about in a minute - there's no denying
that Europa has got an awful lot going for it. Because hidden beneath the moon's icy crust is a
vast ocean - and I really do mean vast. According to our current best estimates, Europa’s global
ocean averages a staggering 100 kilometres deep - by comparison, Earth’s oceans are on average
just 4 kilometres deep. To put that another way, it’s estimated to contain roughly twice as much
water as can be found in all of Earth's oceans put together, despite being smaller than our own moon.
Even better, scientists believe this ocean is in direct contact with Europa's rocky core, allowing
nutrients and other chemical goodness to dissolve into the water, where they could be used by any
alien microbes that happen to be living there. Surface temperatures on Europa can drop
to -220 degrees celsius - for context, the coldest temperature ever
recorded on earth is about -90 - but tidal forces generated by the
never-ending gravitational tug of war between Jupiter and its many moons cause Europa to
warp and flex, generating heat through friction. As of today, there are still plenty of unknowns -
it’s unclear exactly how warm Europa's subsurface ocean might be, we don't know the PH
or salinity of the water it contains, and we aren't really sure exactly what
chemistry can be found there. Even so, there's every chance this icy moon is habitable. The trouble is, even if the hidden world
beneath Europa’s frozen crust is positively brimming with alien life, actually finding it
is going to be a monumentally difficult task. Europa lies at an average distance
of about 630 million kilometres from earth - significantly further
than the likes of Venus or Mars. When NASA's flagship Europa Clipper mission
blasts off for the Jupiter system in 2024, it'll be a good 5 and half years before it actually gets
there. And even when it does, it won't be looking for life - at least, not directly. Because
if there really are aliens living on Europa, they’re buried beneath up to 30 kilometres of
ice that’s so cold it’s harder than granite. That would be a serious engineering challenge here
on earth. On a frozen moon 630 kilometres away, it's an obstacle we simply aren’t
equipped to overcome just yet. ## Enceladus If Europa was the long-time poster child in the hunt for extraterrestrial life in
our cosmic backyard, Enceladus, one of Saturn’s frankly excessive 82 moons,
is very much the pretender to the crown. Which is surprising, because on paper, it
doesn't actually look all that impressive. For one thing it’s absolutely bloody tiny
- with a diameter of just 500 kilometres, you could comfortably plonk it down in between
London and Edinburgh - and its gravity is so weak that if you stood on the surface of
Enceladus and fired a gun directly upwards, the bullet would simply carry on into outer space. Thanks to this undeniable weediness
- and the fact that Saturn is a good 10 times further away from the
sun than earth - for a long time scientists assumed Enceladus would be
nothing more than a tiny frozen blob, with whatever heat it may once have held
in its core having long since dissipated. But that all changed in 2005 when NASA’s Cassini
probe did a flyby of Enceladus, and it observed something remarkable - plumes of water being fired
out into space from the moon’s southern pole. The find was so unexpected that Cassini's
mission orders were changed immediately, with the probe taking a new direction
to fly through this watery ejection. And what it found was salt water -
compelling evidence that, much like Europa, Enceladus' barren, icy crust hides a big wet
secret - a subsurface ocean. Not only that, Cassini also detected simple organic
compounds - potential building blocks of life. As an interesting aside, it turns out that little
Enceladus has been pumping so much water out into space that it single-handedly created one
of Saturn’s rings, known as the E-ring. Scientists had spent decades wondering
why it was that Enceladus appeared to be orbiting Saturn smack in
the middle of this giant ring, and as soon as Cassini picked up
those plumes, the mystery was solved. Anyway, towards the end of Cassini’s
mission, its instruments made one last important observation - evidence
of active hydrothermal vents bubbling away in the depths of Enceladus’
subsurface ocean. That was a huge deal, because many origin-of-life scientists believe
it was around exactly these kinds of vents that inanimate matter first sprang into life
right here on earth billions of years ago. The evidence is still being pieced together,
but there’s a growing feeling that parts of Enceladus’ ocean might actually be habitable
to complex life, and even some extremophile microorganisms found on earth today. Which
is why it’s no exaggeration to say that, right now, this tiny moon of Saturn is
very probably the single most promising place in the entire solar system for us to
go and bag ourselves some bonafide aliens. Of course, any attempt to go and do just
that will face many of the same issues I talked about in the context of Europa - on
average, Saturn is almost twice as far away from Earth as Jupiter is, so getting there’s an
absolute ball ache. And, much like on Europa, if there’s any life to find, kilometres
of solid ice will need to be mined. Of course, there is one key difference
here - Enceladus is helpfully blasting its water from its subterrenean prison, clean
out into space, meaning we won’t need to drill through one of the solar system’s biggest
ice cubes to get our hands on some samples. But sadly, with zero missions
planned for Enceladus we aren’t likely to find out anytime soon, if
there’s life within this tiny moon. ## Titan Enceladus may be the most likely
place to find life in our backyard, but for my money, the most exciting is
another moon in the Saturn system - Titan. As the name suggests, Titan is a
chonky boi. Saturn’s largest moon and the second largest in the entire
solar system after Jupiter’s Ganymede, Titan is almost as big as
Earth, and bigger than Mercury. But it isn’t Titan’s planet-like size that’s
got me all scientifically hot and bothered. It’s the fact that Titan just so happens to be
the only body in our solar system aside from earth where stable bodies of liquid are found
on the surface. It’s a world with wind, rain, and distinct seasons, all of which combine to
create a landscape that’s surprisingly similar to that found on earth, with rivers,
deltas, lakes, seas, and sand dunes. Titan’s also the only moon in the solar
system known to have a dense atmosphere. So far so brilliant… but there
is one small catch. You see, the rivers, lakes, and seas that
dot Titan’s surface aren’t full of water - they’re flowing with liquid
hydrocarbons like methane and ethane. For that reason alone, the surface of Titan
most certainly *isn’t* a candidate for life as we know it. But it may well be a
candidate for something… different. At the start of this video I said that finding
life elsewhere in the solar system would pretty much guarantee the existence of untold
billions of other lifeforms throughout the universe. And that's absolutely
true... except for one small problem. If we were to find evidence
of life on Mars, for example, it wouldn't necessarily mean that life had
originated there independently - there’s always a small chance it hitched a
ride there from earth, or vice versa. As an example, when the asteroid that killed
the dinosaurs smashed into our planet 66 million years ago, it struck with such force that
it blasted billions of tons of debris clear into space. Some of that material will have
crash-landed elsewhere in the solar system, potentially taking some stowaway
extremophile microorganisms with it that could have ‘seeded’ other parts of
the solar system with life from earth. The concept of life travelling from
planet to planet in this way is known as panspermia - which is a fancy way to say we
impregnated the neighbours - and as of today it’s very much a fringe theory that’s well
outside the scientific mainstream for the simple reason that no real evidence backs it
up. But if we *were* to find life elsewhere in the solar system - particularly if that
life bore any similarities to lifeforms found on earth - it would certainly
lend more weight to the argument. If we found life on the truly alien world
of Titan, however, we could be incredibly confident that panspermia wasn’t the cause. Titan
is a world governed by entirely different rules, and earth life would have no hope of surviving
its methane rain and hydrocarbon seas. That’s actually one of the biggest challenges
we’re going to face when searching for life on Titan - it’ll be so different to
anything we’ve ever seen on earth we might struggle to recognise
it as life in the first place. As intriguing as the question of whether
life could be possible on a moon like Titan might be, we’re going to have to wait
until at least 2034 to get any answers - that’s when NASA’s Dragonfly mission is due to arrive
there with the express aim to hunt for life. That’s one of the most frustrating things about
the search for extraterrestrial life - even here in our very own solar system. The distances
involved are so great that everything takes bloody ages. Not to mention the fact that space
exploration costs a pretty penny - NASA has cost the US government about $650 billion
dollars since its inception in 1958. And yet, we humans are a curious bunch, and
collectively we’ve decided that the possibility of learning more about the universe we find
ourselves in is worth the time, effort, and cost. Even as I’m speaking, probes are
streaking through the solar system, heading to many of the planets and
moons I’ve covered in this video. Will they find life when they get there? Your guess is as good as mine. But I
for one can’t wait to find out. Thanks for watching.
