Despite having discovered along the lines of 5000 exoplanets since the search for them
began, we actually know comparatively little about terrestrial ones like our inner solar
system planets.
We know of exoplanet gas giants, hot Jupiters, probably ice giants like Uranus and Neptune
and other giant planets because they’re simply easier to detect than small ones, as
a result we know comparatively little about terrestrial rocky worlds.
But we do know about some.
A good example is the Trappist 1 system, where you have an ultra cool red dwarf star, a very
small one of only about 9 percent the mass of the sun.
This star system is much older than our solar system, coming in at about 7.6 billion years
old, but this is not particularly surprising as red dwarf stars are much longer lived than
our G type sun.
Located only about 40 light years away, this type of target in the search for rocky exoplanets
was favored in being relatively nearby.
And planets were found around it.
In fact, in this system alone, seven terrestrial planets were eventually found, all orbiting
close in to the star in a complicated orbital resonance, a situation that very well may
have existed since the formation of the system.
This is a double edged sword because the tidal forces on these worlds could make at least
some of them intensely volcanic from flexing, much like how Jupiter’s moon Io maintains
its volcanism through being flexed by the giant planet.
These planets are also probably tidally locked, all presenting one face towards the star.
Some of these planets orbit within the habitable zone of the Trappist star and as such could
host liquid water along with the volcanism.
That’s tantalizing for two reasons.
First, when Earth had those conditions, which it still does though to a lesser degree than
the early days, that’s when abiogenesis occurred on this planet.
Second, with the recent linkage between volcanic basaltic glasses and the genesis of RNA, a
proposition that now seems experimentally confirmed incidentally, a show dedicated to
that coming on my Event Horizon channel very soon, and a link to the associated paper in
the description below, then any world with volcanism and water comes on the table as
ideal to at least start forming complex RNA molecules, the starting point for abiogenesis
and the RNA world model.
But we don’t know that much about the Trappist-1 worlds beyond that.
What could shut them down for example is if the planets in the habitable zone do not have
atmospheres.
This is a particular problem in that they orbit so close to a red dwarf that it could
have stripped their atmospheres off early on if they had them, though new models of
red dwarf dynamics seem to show that their flares tend to concentrate nearer to the star’s
poles, meaning that the planets would generally be spared the intense flares associated with
some red dwarfs.
Another issue is that the densities of the planets in the system are known, and they
are low, which may be an issue as well.
As an aside, really tiny stars like Trappist-1 straddle the distinctions between a red dwarf
star and a brown dwarf object.
Given how cool their photospheres are, they actually can have clouds in the form of dust
and condensates.
But this may not be the case for this particular star, there is some evidence of dust but that
it’s distributed evenly all over the star, meaning that in a way this star’s photosphere
is hazy.
Interesting things happen with very small stars.
But the Trappist-1 planets aside, we do know of two terrestrial planets that are associated
with water and volcanism.
Earth and Mars.
Venus may also enter the fray here with further study of its geologic history.
But just the idea that our star system hosted two worlds that had simultaneous volcanism
and liquid water bodes well for the conditions of abiogenesis.
If you have two chances for it in the same star system, then that suggests that these
types of worlds are common in the universe.
But there is a wildcard here.
And that’s water.
While water is an excellent solvent for the chemistry of life, and it’s very abundant
in the universe at least in its frozen form, it can also be somewhat of an issue in that
too much of it may prevent abiogenesis at all if it interferes with the production of
RNA.
Too little water and life does not happen, too much water and it may also not happen.
Only in situations where you have ample water, volcanic geology, but also dry land does it
seem likely at this point that our model of life could arise.
Of course that doesn’t mean there aren’t other pathways, such as environments like
Enceladus and Europa and their hydrothermal vents.
Thankfully, again our star system produced two planets that had volcanism, water and
dry land.
Again Earth and Mars.
But that creates a somewhat big question.
If you have a terrestrial world that has too much water, in other words a global ocean,
and if life managed to get a foothold on such a world either through abiogenesis or panspermia
and then undergo Darwinian evolution and reach complexity and intelligence, then could it
develop a technological civilization advanced enough to show a technosignature such as a
radio signal?
The answer in a nutshell is probably not.
We don’t really know how common global ocean exoplanets are, we haven’t even definitively
seen one yet.
But if they are very common, along with locked-in ice shell oceans, then the universe could
be teeming with life, even intelligent life, but most of it is hopelessly aquatic.
Mastering technology in an oceanic environment is a problem.
Intelligence in an aquatic environment on the other hand, seems to happen, Octopi and
some of the Squid can be very intelligent, though the lack of land would preclude situations
like earth where much of the ocean's intelligent life descends from land mammals that adapted
to go back into the oceans.
So at least hypothetically, increasing intelligence may evolve on an ocean world if there is pressure
for it to happen.
If some situation regarding predators for example, or some factor that favors increasing
intelligence, or even just enough time, could trigger the occurrence.
On earth for example after 4.5 billion years, we have a group of highly intelligent hominids,
homo sapiens are our immediate but now extinct relatives like homo erectus, but also a group
of up and comers, species like chimpanzees, gorillas, cats, dogs, some of the birds, and
so on that also have some level of intelligence, and with the right evolutionary paths they
may someday become technological species themselves.
That could mean that the older the world, the more likely it is to have intelligence,
so planets like the Trappist-1 system that are billions of years older than our solar
system may have an abundance of intelligent life of varying degrees.
But if it’s more often than not on an aquatic planet, then that may prevent most technology,
both because of the environment, but also physiology.
Life adapted to operate in water is probably going to lead to convergent evolution.
This is where very distantly related species, or entirely alien ones on an exoplanet, tend
to develop similar features because those features work best in water.
The shark and the dolphin come to mind here, they both have fins, but for very different
evolutionary reasons.
They share a similar body shape and means of locomotion through water.
Why?
Because it works, and evolution naturally fills these niches leading to two very similar
appearing creatures, but with very different evolutionary histories.
Because of this, you might expect certain aquatic species bioforms to be common in the
universe, you might go to an exoplanet with an ocean and see something that vaguely resembles
a shark for example.
Or an octopus.
But what you don’t see animals in oceans doing is harnessing fire.
And that’s somewhat of a show stopper, because to build a civilization, the first thing you
need to do is learn how to make tools, which is very difficult to do with fins, and then
harness fire, which is impossible under water, though one wonders if underwater volcanoes
might offer a rather imperfect option for a replacement.
This leads to a scenario where ocean worlds exist that have no land, therefore no matter
how intelligent the species present on it get, they can’t ever escape the confines
of the water.
If this scenario reflects the bulk of earth-like exoplanets, then the solution to the Fermi
Paradox is that the universe simply has too much water for intelligent life to be common.
The ultimate in irony really, in that which allows for life, also tends to prevent technology.
But this scenario may not be all that likely given the aforementioned fact that our own
solar system has earth and Mars.
And it’s also worth noting that volcanism tends to like to build dry land, see the Hawaiian
islands.
And this leads to some interesting strangeness about our solar system.
The tallest mountains in the solar system tend to be volcanic in nature.
This is certainly true for earth, while Mount Everest is the tallest mountain on land, the
highest point on earth at 29,032 feet, it’s beat by the volcano seamount Mauna Kea, which
from its base rises 33,500 feet.
Yet Mars sports the truly astonishing volcano Olympus Mons, and despite Mars being smaller
than earth, this volcano dwarfs anything on this planet.
It comes in at about 25 kilometers in height, or about 80,000 feet, and its footprint is
comparable in size to the state of Arizona.
And recent evidence shows that parts of it are geologically young, meaning that this
sleeping giant may be active and could erupt again in the future.
Ultimately gravity plays a part in the sizes of these mountains, as does weathering, and
while Mt.
Everest does continue to grow, it can’t do it forever, and most estimates place it
probably at the upper limit for earth, though this is debated.
Likewise, Mars with its lower gravity, was able to produce a bigger volcano, so much
so that it clears most of the atmosphere and usually can be seen peeking through during
Mars’ periodic global dust storms, it probably can’t have produced much bigger.
While a situation like Mt.
Everest requires continental drift and impact, giant volcanoes do offer a path for dry land
on otherwise entirely oceanic worlds.
And any volcanic dry land could in principle allow for the formation of RNA.
Past the formation of RNA however we enter the land of abiogenesis mystery again.
RNA is a molecule, but it is one that can store information, but how that becomes life
itself is still a mystery, as is how DNA comes about from the chemistry of RNA.
But the fact remains, it did happen here, and the recent finding about RNA really favors
Mars strongly as a candidate for at least former microbial life.
What this means for exoplanets is largely unknown, other than if the process is straightforward
then it favors them.
Given that volcanism appears to be a component for life, the oceanic world solution doesn’t
seem like it would happen enough to account for the great silence.
At the same time though, it might bear the implication that worlds with too much water
simply never form life, or worlds with no volcanism.
The ice shell moons might similarly be devoid of life for lack of the conditions needed
to form RNA to get the process going.
That in itself is a solution to the Fermi Paradox, the universe simply has too much
water.
But it does lead to an interesting scenario.
If you had a world with only a few volcanic archipelagos on it representing all dry land,
or worse a single island, as in Arthur C. Clarke’s novel The Songs of Distant Earth,
for fun let’s call these Thalassa Worlds in homage, you could have a very unpleasant
situation that could prevent civilization on its own.
Not enough resources for any land life there to get very far, or ever sustain a large enough
population to move forward, or presents conditions so harsh that all time is spent on survival,
and intelligence is simply never turned towards the invention of technology.
I cant help but to find this one a rather sad solution to the Fermi Paradox.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently worried about contact
with aquatic alien intelligences without knowing they were once aquatic.
Imagine interacting with an alien at a banquet.
Everything’s going swimmingly until the chef brings out a plate of calamari, and the
alien just looks at you and says “What have you done?”.
An awkward and unsettling first contact indeed and be sure to check out my books at your
favorite online book retailer and subscribe to my channels for regular, in-depth explorations
into the interesting, weird and unknown aspects of this amazing universe in which we live.