In previous videos on the Fermi Paradox we discussed a number of solutions to the question
of why life seems so rare in the Universe. One of the more popular scenarios is called
the “Rare Earth” option. But rather than just doing a video discussing that in more
detail than we already have we’ll use it to segue into a separate series.
We’re going to look at all the weird planets and even non-planets where life might just
conceivably get a foothold, and while we will still be raising all the problems and hurdles
life would have existing in these places we will be looking at it from a more optimistic viewpoint.
To commemorate the fly-by of Pluto taking
place at the time I’m recording this, we are going to start off by looking at how life
might be able to live on a place like Pluto. A relatively small planet far from a star’s
warming light. So we’ll be looking at Pluto and worlds
like Pluto in this first installment. We’ll look at how they might conceivably host life
and also how such worlds might be colonized to be homes to humans or other technological
species. In future installments we’ll look at everything
from worlds around red dwarf stars or on moons around Gas Giants. Or even in Gas Giants,
both those near stars or rogue worlds out in the interstellar void. We’ll look at
how life might live in a comet or asteroid. We’ll try to cover all the reasonable options
and even some of the crazier ones. Hit the subscribe button if you want to be
alerted when those new episodes come out. So if you’ve seen previous videos you’ll
probably notice I’ve started adding in some animations. We’ve got two other new features
as well. First, we’ll be trying to keep the videos shorter. [Hurray]
And Second, I’ll be experimenting with adding in subtitles [Hurray]
I know I’m a bit hard to follow sometimes and remind people of some fictional characters.
If you’re curious it is a speech impediment, not an accent.
Hopefully with subtitles I’ll be easier
for some of you to follow. Assuming it works of course.
So let’s get started. I want to emphasize that this is a very hypothetical video, personally
I doubt we’d find life on Pluto, even simple organisms, but we can’t rule it out. It
isn’t just that such life might run on weird chemistry compared to our own, there could
be habitable pockets where Earth-like life could live.
What about really alien life though? Pluto and worlds like it are basically over-sized
comets. Most of their material is stuff that would melt or evaporate if it were on Earth.
Ice, ammonia, methane, carbon dioxide and even oxygen and nitrogen are frozen solid
there. But hydrogen and helium aren’t. Hydrogen doesn’t freeze till it gets even colder
than Pluto gets so worlds like it, even ones in the interstellar void, could easily have
liquid hydrogen in abundance. When we’re talking about life they key thing
is a power source. Hydrogen burns, so you could conceivably have an organism on the
super-cold worlds that drank liquid hydrogen and frozen oxygen and used that as it fuel
or food. Pretty out there but probably not impossible.
But what about Earth-like life? Is that at all possible?
Throughout this series we’ll mention over and over that they key thing life needs is
a fuel. It needs a power source. But to be at all Earth-like it needs pressure and temperature
too. If you’re far from a sun your options are
limited, but we’ve got two. First, a lot of worlds have pockets of radioactive materials.
Those decay with time but are also a lot more plentiful for that reason when a world is
young. Uranium, potassium, and other substances will give off some warmth just as they do
for Earth. When planets form matter falls down on them and impacts, so they tend to
be very hot from absorbing all that and they may have a steady flow of meteor impacts adding
some heat. Between radioactive materials and impacts a planet may be warm, and retain warm
pockets deep beneath its surface. There’s also tidal heating. If a planet has a moon,
and Pluto does, actually it has several, then the constant distortions of gravity yanking
on the world can keep it quite warm. This is what keeps Jupiter’s moon Io a ball of
molten lava. So while surface life walking around breathing
air probably isn’t in the cards with anything like normal Earth-life there could be deep
and massive oceans on these planets. Indeed we’re pretty sure Pluto does have underground
oceans and that even it largest moon, Charon, might have some.
Where you’ve got liquid water being churned around with minerals dissolved in it you have
the possibility for life. We still don’t know what started life on Earth, or if our
main candidates of underwater thermal vents, so called black smokers, are the only way
for it to emerge if that is what started things off here. But regardless of how it gets started,
once in place life could be able to thrive in any ocean so long as there’s some power
source stirring up the water. Throughout this series we’ll see that there’s
a lot of candidates for that which wouldn’t even qualify as a dwarf planet like Pluto,
let alone an Earth-sized planet. Now complex life, especially intelligent tool
users, is a different story. Ocean life obviously can’t support fire or many other technology
precursors like metallurgy, pottery, glass blowing, and even basic chemistry. It is kind
of hard to mix solutions in water. There’s also the matter of ‘thriving’
being somewhat relative. We have a long and dense food chain because everything runs on
abundant sunlight. If you’re familiar with life down in caves or the deep ocean you know
those are all optimized to run on very little energy and they still get most of that from
debris flowing down from where there is sunlight. Some life-bearing Pluto equivalent could easily
have less than a percent of our biomass and still all spread out and it is rather hard
to develop a civilization when you are spread out. Our hunter gatherers needed around a
square mile per person to live, far more in tundra or desert climates, and that limited
them a lot on developing. If you’re a hundred or a thousand times more spread out to gather
food you’d have some serious roadblocks to forming civilizations. So we can’t rule
it out, but where simple life, and even animal life, are reasonable expectations off worlds
like Pluto that expectation would have to be far smaller where anything really complex
like us is concerned. The next thing to consider is what to we mean
by worlds like Pluto. Pluto’s small, smaller than our own moon even. It’s cold. And it
has a large moon that isn’t just tidally locked to it, but to which it is tidally locked
to as well. Which of those factors apply to what we’ve been talking about?
Well a bigger planet, say Earth transported out there and left to orbit for a billion
years, would behave a lot differently. It will have a thicker atmosphere, Pluto has
one but barely worth mentioning, just like the moon has one. Earth’s atmosphere contains
virtually no hydrogen except where it’s locked up in a molecule like water or methane
because molecular hydrogen doesn’t stick around on warm planets. But it’s the most
common substance in the universe so an Earth Mass planet could easily have ocean and atmospheres
made of molecular hydrogen. It would probably be warmer too, since heat loss in a vacuum
is all about surface area. More surface, more heat loss. Pluto might have only about 0.2%
of Earth’s Mass but it has nearly 3% of its surface area, a 15:1 higher ratio. So
when it comes to heat derived from radioactive decays bigger planets will stay warmer. If
we’re pondering a low-temperature life form that uses liquid or gaseous hydrogen instead
of air or water the way we do you could have life swimming around in surface oceans of
Earth-Mass worlds that weren’t even near a star.
As to a Pluto-like world in mass and composition near a star, it would probably evaporate.
Pluto is more like a giant comet then a planet or asteroid. Another reason it has a relatively
large surface area, it just isn’t very dense. But a less massive world than Earth, even
one less massive then Mars, can actually retain a thick atmosphere. There’s a misconception
we get from the Moon and Mars that gravity is key factor there, which it mostly is, but
there’s a lot more leeway on it then people tend to think. We’ll discuss that in a future
video on life for more or less massive planets. Last thing. What about colonizing a place
like Pluto? Can we, with the kind of technology we have now or can reasonable predict we might
get live on a place like Pluto? The answer is basically a straight YES. Even
without some power source like fusion, or old school nuclear fission, we can power ourselves
there. Burning hydrogen and oxygen, or methane and oxygen specifically on Pluto isn’t very
viable because there’s not a lot of oxygen around except as water but there is some and
other Pluto-like worlds might have more. Plus not everything needs oxygen to burn, for instance
the spacecraft flying by Pluto right now has Hydrazine thrusters, and that’s a mix of
nitrogen and hydrogen, both abundant on Pluto, and doesn’t need oxygen to create thrust
and heat. So chemical power isn’t totally ruled out even for Pluto let alone other parallel
worlds. Nor is solar power. The sunlight out there
is barely a thousandth of what it is here, in intensity, but one watt per square meter
is still nothing to shrug at. That’s actually brighter than the night under a full moon.
A 10 watt LED light in a room in your house is delivering light comparable to what you
get from the sun out there, so it isn’t dark. What’s more, you’ve got options
like solar mirrors. The idea of creating planet-sized mirrors to reflect more sunlight onto a world
sounds very crazy but when you’re talking about mirrors that only need to be as thick
as paper, or even thinner, manufacturing ones the size of whole planets can be done with
less mass than you’d have in even a very small moon no bigger than a modest mountain
on Earth. If you’ve seen my original YouTube video, Megastructures, then you know doing
something like that is actually very modest compared to some of the projects we envision
getting ourselves up to in the future. So even if we never figure out fusion these
freezing cold worlds aren’t necessarily off our radar to put habitations on, though
obviously that would be ideal followed by good old fission power with something like
Uranium or Thorium. Gravity isn’t an issue either. It’s very
low on Pluto, about 7% of Earth normal, compared to 16% on the Moon. But as we also mentioned
in that Megastructures video, centrifugal or spin-gravity isn’t limited to use just
in zero or micro-gravity environments. Instead of using a spinning cylinder you just slope
the floors to combine natural gravity with spin. Just like how water in your washing
machine will form a slope surface when spinning as gravity and centrifugal forces add their
power together, you can do that on low gravity worlds to create an effective decent gravity.
You don’t need to build sturdy surface domes either, you dig in a few hundred feet deep
on Pluto and the pressure of the ice over you will keep pockets of air at normal Earth
pressures. This would also protect you from cosmic rays and micro-meteors in the absence
of an atmosphere and magnetosphere. You’d have to artificially light and heat
the place so you could grow food but we can do pretty dense and efficient hydroponics
when we need to. So, in summary, can we colonize a place like
Pluto? Yes. Can life evolve their naturally? Quite possibly, though not likely anything
we could chat with. I hope you’ve enjoyed this first video on
planetary habitability. Don’t forget to hit the like button if you have and subscribe
if you want to be alerted to future ones. Feel free to leave a comment, I read them
all and try to reply to questions, and check out my other videos. Have a great day and
thanks for watching!