For most of my life as a space enthusiast there were planets in the solar system that
we had not visited.
I well remember at age fourteen watching the first visit humanity had ever made to the
planet Neptune with Voyager 2 in 1989.
Here was a planet that had been discovered in 1846 that we had never seen close up.
After that there remained one planet in the solar system, at least before its demotion
that we had never seen.
Pluto.
But some thought had been put into what it might be like.
For example, scientists worked out that because of Pluto’s rather eccentric orbit, it would
at times when it was closer to the sun likely have an atmosphere, but then that atmosphere
would freeze out when it was further from the sun, leaving it effectively the only planet
in the solar system that can have an atmosphere during part of its year, which is 248 of our
years, but no atmosphere at all during another part.
But beyond that, there simply wasn’t much known and Pluto was presumed to essentially
be a boring dead ball of ice and rock.
And then we found it was far from that when the New Horizons probe did its flyby of Pluto.
It revealed a dynamic world with varying geography, mountains, and evidence of wide scale geologic
activity.
It was even suggested that Pluto might be an ice shell, and host a subsurface ocean
of liquid water in a similar situation to the ice shell moons of the solar system.
But Pluto hinted at something more may be going on with it.
A year after the flyby of Pluto by New Horizons in 2015, something was discovered on its moon
Charon that may have very far reaching implications.
Pluto and its largest moon really may more accurately represent a double planet, due
to the barycenter of their orbits not not lying within either of the bodies.
This also means that materials from Pluto are exchanged onto the surface of Charon.
Scientists found that reddish stains on the north pole of Charon are made up of tholins.
In other words, organic materials.
Tholins are organic molecules that form in nature without life, but rather they may be
integral ingredients for life to arise.
They are produced by gasses in Pluto’s atmosphere that can escape and deposit on Charon, which
orbits only about 12,000 miles away from the surface of Pluto.
This has presumably been going on for potentially billions of years, forming the staining.
This means that Pluto may well have all of the building blocks necessary for the emergence
of life in its subsurface ocean.
Whether this has actually happened is unknown, but one major factor in this would be the
exchange and interaction of that ocean with the surface of Pluto.
This has recently gotten more interesting.
In a paper by Kelsi Singer and colleagues, link in the description below, they detail
the discovery in the New Horizons data of a network of ice volcanoes on the surface
of Pluto.
And even more interesting, they appear to have erupted relatively recently.
Pluto is an unbelievably cold place, averaging 387 below zero fahrenheit, 232 celsius, water
on its surface is essentially a rock.
But molten water along with ammonia or even methane in the form of a slushy lava of sorts
could briefly exist and flow on the surface.
Evidence of these flows has been detected, essentially making some of Pluto’s mountains
into active ice volcanoes.
Cryovolcanoes have been seen in the solar system before, but nothing quite like the
ones on pluto.
Here the cryovolcanic flows would be somewhat strange to see.
They’d be slushy, or even paste like in nature before quickly freezing solid.
This leads to dome-like structures and terrain that’s not really like anything else in
the solar system.
And it seems to be ongoing, the areas where the flows lack impact craters indicating a
young surface.
The observed ones in the paper seem to have erupted between 100 and 200 million years
ago, but it may also be an active process that will happen again.
This bodes well for the existence of the subsurface ocean.
It’s possible for these kinds of bodies to have subsurface oceans early on, only for
the ocean to later freeze from lack of geothermal heating or gravitational flexing to keep it
going as is the case with Europa and Enceladus.
But given that the activity at Pluto is so recent, it tends to suggest that the liquid
water ocean is still there in some capacity and has been for a very long time.
It also indicates that Pluto’s interior may be hotter than some models have predicted.
Other work has also indicated a warmer Pluto and an active subsurface ocean.
Pluto’s surface shows evidence of fracturing that seems to be the result of stretching
on the surface.
That could be caused by a subsurface ocean moving around beneath.
Even stranger, there is some evidence that the entire surface of pluto has re-oriented
itself, which would be possible only if there was an almost frictionless layer below, in
other words liquid.
More, the cracking in the surface showed wildly varying ages, all the way back to Pluto’s
ancient history not long after its formation 4.5 billion years ago.
Essentially the planet would have formed by accumulating ice and rock and when enough
radioactive material was present and decaying as the planet differentiated then the ocean
would have been formed.
As Earth shows, this is long enough to have potentially spawned at least microbial life,
probably around geothermal vents on the ocean floor of Pluto.
But this process isn’t going to last forever.
As the radioactive materials in Pluto's core decay and dwindle, so will the heat, and the
ocean will eventually freeze solid.
This opens up a really interesting possibility in the universe at large.
Given that we have so many objects in the solar system that appear to be ice shells
over liquid oceans, which includes most large moons of the solar system, that also means
we have many chances for life in the solar system above and beyond the planets.
There are more ice shell moons with suspected oceans in the solar system then there are
the three planets that may have once had liquid water, earth, Venus and Mars.
This may mean that life tends to occur more often under shells of ice in oceanic environments,
specifically moons and minor planets, than it does on full on planets like Earth.
And given that some of these oceans that depend entirely on radioactive decay for the heat
won’t last forever, it’s entirely possible that we live in a largely fossilized universe
as far as life is concerned.
In fact, very good fossilized evidence.
The ecosystems of these worlds which could be billions of years older than our solar
systems may at some point simply freeze solid, along with all life in them.
And while everything would be extinct, its remains would be very well protected under
a thick layer of ice to just sit there for untold amounts of time as a record of what
once was at that world.
Imagine alien biologists combing the galaxy for these formerly habitable zones and studying
the frozen evidence of their ecosystems.
Or more, given that this is all dependent on the amount of radioactive materials in
the cores of these worlds, which may vary dramatically depending on where you are in
the galaxy, it may be possible for a situation to happen where an ice shell minor planet
had life arise, only for the ocean to eventually freeze solid causing wholesale extinction,
but as the aging star it orbits goes into a red giant phase and remelts the ice, the
remaining organic chemicals from the previous life could give rise to a whole new iteration
of life on that world.
In other words a second abiogenesis spawned from the first.
This process is thought to be happening at Pluto if indeed it still maintains a liquid
water and ammonia ocean.
It may be that the ice shell of that dwarf planet has thickened significantly in more
geologically recent times, leaving something along the lines of an ocean about 200 kilometers
thick.
The chances for life being there are less, however, there isn’t as much energy at Pluto
as there is for Europa or Enceladus, but it is possible that it may harbor some kind of
life.
And this opens up even more possibilities.
If Pluto has turned out to be an ice shell, then any of its transneptunian analogues may
just as easily be ice shells themselves.
A good candidate here might be Eris, which is very similar in size to pluto.
Or any of them of a sufficient size.
And the kicker here is that we probably don’t even know a fraction of these kinds of objects
that lurk beyond the orbit of Neptune.
We’re not even sure there isn’t a full on planet in distant orbit of the sun, or
even several, and with the minor planets like Pluto and Eris the number could conceivably
be enormous.
This would mean that the solar system has many, many chances for spawning life in liquid
water than what we currently know.
The ingredients are there; water, energy and chemistry.
And that translates to the universe at large.
If minor planets can support liquid water oceans, at least for a time, through radioactive
decay then so can rogue planets, even large terrestrial ones, wandering interstellar and
even intergalactic space.
This would indicate a universe full of liquid water environments that as far as we know
should be habitable and should allow for the possibility of life.
At least microbial.
But we don’t really know how common it is for microbial life to make the leap to multicellular
complex life.
We just know that happened here, but it took well over a billion years for life to make
the leap.
It’s possible that’s a rare occurrence and that simple life rules the universe, but
complex life is rare.
But there may be a clue here in a recent discovery in science that may give an insight on just
how this happened, and allow us to determine if it would be common or rare in the universe.
Before 2020, it wasn’t clear how simple life became complex, or the prokaryotic to
eukaryotic leap.
From what we could tell, it appeared that the leap just happened out of nowhere and
very simply bacterial cells became very complex almost as though overnight.
But the story had to be more complicated than that, there just wasn’t any evidence to
shed light on it.
This was a problem because a leap it was, all of a sudden cells had mitochondria, which
were thought to have one been independent organisms.
Yet here a cell apparently ingested one without digesting it and somehow everything worked
out boosting the energy of the cell.
And there were other things, nuclei appeared and lysosomes that caretake proteins in cells,
and skeleton-like filaments that hallmark eukaryotes and allow them to move and change
shape.
All of this stuff seemed to come out of nowhere, some common ancestor that lived several billion
years ago.
But that also hinted that there was more to the story and that we had some missing links
in the process that led to the leap.
Clues however finally started surfacing in 2015, with a discovery of DNA from the floor
of the Arctic ocean that seemed to indicate still living archaea that were somehow related
to Eukaryotic life.
They’re called Asgard archaea and at the time of the discovery of the DNA traces, another
team in Japan was studying an organism that turned out to be one.
Known as Prometheoarchaeum Syntrophicum, these things qualify as slow motion life.
Given the very cold water they live in, they take an unusually long time to divide and
they eat methane.
Most of the microbes we see can divide on the order of minutes or days, whereas these
take nearly a month.
And they are quite simple.
Prometheoarchaeum is simple life.
It’s just DNA and proteins, and lacks the structures seen in Eukaryotes.
Yet it uses the same specific types of proteins that allow Eukaryotes to have the complex
structure they do, suggesting that these useful proteins predate Eukaryotes and were being
used by some microbes for Eukaryote like behavior, but for a somewhat different purpose, in this
case to form branching structures from what is initially a tiny spherical organism.
In other words, somehow in the transition stages between prokaryotic and eukaroyotic
life, these proteins were somehow repurposed and enabled more complex structures.
And it might also give a clue on how something can ingest something else, like a mitochondria,
and not digest it.
The view of these types of microorganisms is that they are predatory, but Prometheoarcheum
isn’t.
It’s more like a barnacle that attaches to other microorganisms and eats fragments
of proteins floating by in a symbiotic relationship with the other organism which feeds on the
waste, and provides the compounds it needs, and may have provided a way to ultimately
ingest a mitochondria and incorporate it into its own make up.
But at the same time, it has to be said that this organism is alive today, and conditions
billions of years ago may have been very different.
But it’s at least a clue, and if the leap between prokaryotic and eukaryotic life wasn’t
such a chance event, but perhaps an inevitability of the situation, then that actually dissolves
the biggest great filter there is in astrobiology.
Complex life could then be seen as probably very common, if further work into the origins
of this microbe indicates that its situation stretches back billions of years.
But that doesn’t speak for intelligence.
Even rarer perhaps is the evolution of intelligent life, which may not be possible under an ice
shell.
It could be a situation that such a thing can only occur on land, while intelligent
animals have developed in oceanic conditions on earth, they haven’t launched any rockets
despite having a head start on land life to evolve it.
This is the “ocean life is too easy” scenario where survival is easy enough in an ocean
to not need that much intelligence, but life on land does favor intelligence for survival.
This may mean that any ocean worlds with no land in the universe do not ever develop technological
life, and ice shell moons and planets only ever develop simply microbial life and the
environment simply doesn’t allow for more.
Or life could find a way, as they say, and entire diverse ecosystems could exist under
shells of ice.
Think space whales, alien octopus-like creatures plying the ocean floor and squid analogues
jetting around, and even extraterrestrial fish-like creatures.
Or jellyfish, which look alien enough even for earth.
Or how about bioluminescence or creatures for which we have no analogue for on this
planet borne from adaptations unique to an ice shell moon and not present and guiding
evolution on earth.
It would be an interesting situation indeed if intelligent technological civilizations
are rare in the universe, but life is not, even complex life.
The universe would be like a nature preserve, like an untouched North American continent
where humans in the distant past found and spread through, we would do the same in a
universe like that, learning new ecosystems in most star systems we visit by drilling
through ice.
It may even be that if you could talley up all of the exploratory vehicles of all civilizations
in the observable universe, you might find that submarines outnumber spacecraft.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently addressing those
that have noticed my video release cadence has somewhat dramatically increased as of
late.
I’d like to say It’s because my new studio and my audio setups are complete and I have
a lot of material to cover currently, and it’s now down to just efficient full-time
production for both this channel and event horizon, but we all know it’s because ANNA’s
out shopping for spare parts and the possum’s on vacation in the Himalayas and not pestering
me in the science lair and be sure to check out my books at your favorite online book
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weird and unknown aspects of this amazing universe in which we live.