There’s an old theory known as Panspermia, which hypothesises that life got its initial leg up on Earth (around 4-3.5 billion years ago) after a long journey across space. According to this theory, (which at the very least is quite reasonable) the ingredients and precursor molecules for life hitched a ride on comets and asteroids and reached earth early in its history, when these objects impacted our planet. As for where these molecules and ingredients came from…well, that is a real chicken and the egg type question, and one I will be exploring in more detail in future posts as well as videos.
Not all astrobiologists agree with this of course. Each to their own. Science and seeking the truth is all about disagreement. I’ll leave the debate alone and for the purpose of this post assume that Panspermia is a pretty valid idea.
This post (and the YouTube video it will eventually give birth too) is essentially a piece of speculation. Looking into the future of space exploration, what is waiting for us out there?
Europa has been the hearts desire of many an astrobiologist for decades now. Ever since the Pioneer 10 probe rushed past back in 1973 and sent back the first pictures it’s been a bit of a rock star. Why? Because it ticks a whole lot of boxes on the “Things could live here because…” checklist.
Things could live here because….
Let’s look at some of those boxes. And why they’re important. First of all:
1: Europa is now widely believed to harbour a substantial subsurface ocean: of actual honest to gosh water. How have we come to this conclusion?
Take a look at the surface of Europa.
It sure is striking. Huge channels and streaks criss cross the moons frozen exterior.
And that’s about it.
No craters? Callisto is part of the Jovian family as well, and is the most heavily cratered object in the solar system. Compared to Europa Callisto is a teenager with weapons grade acne.
Europas surface is geologically new, having been resurfaced recently (in geological terms). Something is wiping the slate clean on Europa, and this is our first clue that Europa is special. Something under that icy shell is acting upon the surface and rearranging it.
Astrobiologists think it’s water. A lot of it. Europas surface is basically a shell of ice, rafting and fracturing like pack ice on Earth. Essentially vast swathes of pack ice remodel the Europan landscape and are thought to be it’s version of our plate tectonics.
2: Some time ago, none other than the venerable Charles Darwin postulated that life began in a “warm little pond”, whereby the right combination of mineral salts and energy resulted in the first biomolecules. Ever since this first speculation, forwarded in a private letter from Darwin to his friend Joseph Hooker in 1871, science has placed an emphasis on water as the likeliest birthplace of life on Earth. Darwin believed in a warm little pool, many other theories have thought bigger, fingering the ocean as the culprit. Whatever the case may be, and whatever supporting evidence gives testament to it, water (for now) is the one thing no life can exist without.
And Europa has a lot of it. The deepest point on our planet lies at the bottom of the Marianas Trench, some 12 kilometres below sea level. That is deep to be sure, but the abyssal plains of the world’s oceans are on average about 4 kilometres beneath the waves. Europas subsurface ocean averages a cold dark 62 kilometres deep!
Where do the minerals fit into this? Patience, grasshopper!
Jupiter pumps out extremely high levels of electromagnetic radiation. This is, of course, a constant engineering hurdle for the various missions that have paid the gas giant a visit. It’s extensive family of moons: some 67 in total are constantly immersed in this field, which interacts with various bodies in various ways. Europas magnetic field is no different, and is an induced magnetic field. This is a special kind of magnetic field produced when an electromagnetic field is passed through some kind of conductive material. In the case of Europa this material is believed to be an ocean, brimming with conductive mineral salts. Such an ocean would be a vast salty brew, fulfilling Darwin’s vision somewhat.
What of Darwin’s energy source? To understand this a little more, and to see what it means for Europa, we need to understand that all life requires an energy source. On Earth, the vast majority of life is solar powered. What does this mean? You can’t just go outside and photosynthesise! You need to go to the fridge and get a snack. Food keeps you going, right?
Absolutely. But where did that food come from? Whether you’re a vegetarian or a carnivore, ultimately every single thing in that fridge of yours exists because of the sun. Either it grew from the ground, something came along and ate it, or something bigger came along and ate that something. The sun is at the base of this very simplified food web, and it’s been doing it forever of course.
No solar power is not some fandangled idea. Renewable energy has been around, well, since before life began. The sun provides energy not only for Earth’s climate and hydrological cycle, it also fuels all photosynthesis on Earth. Plant life not only provides food and oxygen for animal and fungal life, it also contributes to climatic processes. Yes, the Sun is really important.
Ah, you think, how does any of this relate to Europa? The frozen moon is a bit further out from the sun than warm little earth, at about 485 million kilometres. Not much use for solar power out there! Well it turns out that not all life on Earth is completely dependent on the Sun after all.
These are exciting and mysterious places, home to a bewildering and diverse array of lifeforms. They are found where life seemingly has no business existing, and yet there they are: on the vast abyssal plains of the ocean floor. Miles away from any sunlight, subjected to pressures and extremes that would kill us instantly life thrives in a hostile alien world.
These ecosystems are based not on photosynthesis, whereby sunlight is converted into a food source for plants, but chemosynthesis. Down here life has found a way, to steal a phrase from “Jurassic Park”. Literally, bacteria have evolved to survive at the hellish temperatures and pressures around these hydrothermal vents, where the water can reach temperatures of over 350 degrees Celsius. With nothing but a rich mineral brew spewing from these vents out onto the ocean floor, these bacteria have learnt to make use of this brew. These bacteria then form the basis for some of the most intriguing ecosystems on the planet. These vents are an oasis of life, all alone in the abyssal night.
Does Europa have the capacity for such vents, far beneath the ice? On Earth, the vents are geothermally heated. Earth posesses a core of molten iron, heated by slow radioactive decay of elements from the formation of the planet 4.6 billion years ago. This internal heat eventually reaches the upper mantle of the planet, seeping through in more threadbare regions of the Earth’s crust, Europa is heated by Jupiter itself. As the moon orbits the gas giant, tidal forces act upon it, squeezing and massaging. Resulting frictional forces are believed to sustain a heated core, which, just like earth, could provide energy to keep systems of hydrothermal vents running on the abyssal plains of Europa.
So. Europa may tick some really important boxes, for the existence of life. Water: definitely check. Minerals and organic compounds: check. A source of heat, to power possible life: check.
Now the only thing for it is to visit; to get through the icy shell to the ocean beneath….
To be continued….
Next post takes a ride beneath the ice.
17th November 2017:
And here is the video for which this post formed the script:
So. We exist here on our rock, as it flies around our medium size main sequence star, and slowly but surely begin to realise that we are not quite as special as we think. Sure, we’ve come a long way. This isn’t necessarily a good thing. Progress is literally a moving forward. By this rationale the human race has made astonishing progress in the last two hundred years. I won’t rattle off the myriad achievements we’ve ticked off the sentient species bucket list, but we’ve done a lot- let’s just leave it at that. The mobile device or computer you’re reading this post on is one tiny part of that progress.
But one piece of wisdom we have gained in the midst of all this gadgetry is this:
We are not the centre of the Universe.
There. I said it.
Ever since Copernicus, Gallileo et al realised that Earth revolves around the Sun, much human progress and thinking has revolved around the fact that no, we are not the focal point of creation, life has gone on before us (and will carry on long after we’re gone), and that our very planet is turning out to be not quite as unique as we thought.
It seems like every second week a new exoplanet is being discovered and added to a growing bestiary of worlds. Most of those worlds are nothing like earth: but I believe it’s only a matter of time. In our own solar system water; that miracle ingredient for the appearance of life is turning up everywhere we look.
Water is a bit of a superstar. I won’t espouse it’s virtues here, but suffice to say, absolutely no life (as we know it) can exist without it. Water is turning up everywhere it seems. Here are a few examples. I will begin this tour with with the inner planets of the Solar System. For the sake of brevity I will only glance on each location. At this point in time current thinking is focused on certain moons in the outer solar system: “outer” meaning beyond the asteroid belt. Water appears to be abundant as we head outward, but I think it fair that the terrestrial planets get some love too. After all, should humanity ever sort out its myriad problems and eventually stops just dipping it’s toes in the water, one of these worlds might just be a new home for our species. The presence of water would be highly advantageous.
Let’s put together a little list of locales in the Inner solar system where water is thought to exist. I will include Earth here as the first obvious example.
Home to over 7 billion talking monkeys, loads of beetles, bacteria and a whole pile of other beasties all jostling about on the Tree of Life. A middle aged planet, third from it’s parent sun in a non-descript solar system moving quietly through the Orion Arm of the Milky Way Galaxy. There’s a lot of water here, about 1,260.000,000,000,000,000,000 litres. That’s 1260 million trillion litres.
Now, obviously that sounds like a lot, but if you want to really get an idea of how much water this is, just ponder this. Of all water on earth, 96% is saline. Four percent exists as freshwater. Of this four percent, sixty eight percent is locked up in ice and glaciers. Thirty percent of the remaining freshwater is groundwater, and thus not accessible to all and sundry.
About 0.006 of this four percent exists in rivers and lakes.
This tiny sliver of the total global water pie keeps all of us talking monkeys alive.
So, where is this going?
There are vast amounts of water on Earth. But Earth is only one of 8 other planets in the solar system. There are also five dwarf planets, of which Ceres and Pluto are the most famous examples, and 182 moons orbiting various objects and bodies throughout the solar system.
Say again?, you ask. “Ben, are you out of your gourd? Isn’t the Sun that great big hot thing at the centre of the solar system? You know, that really hot thing that is so hot we can feel it’s heat here, from 93 million kilometres away?”
Yes, Dear Reader, the sun is that big hot thing. But researchers have demonstrated the existence of water vapour in the central cooler regions of sunspots. Apparently, so the science goes, these regions are just cool enough that hydrogen and oxygen can get all chummy and form water. Now, liquid water (and obviously ice) are out of the question, but there you go. There is water on the sun. Next.
Poor old Mercury has never had a good trot. The closest planet to the sun, Mercury got baked clean millennia ago. No atmosphere worth mentioning exists, and so you’d think that’d be it. It’s just a barren hellish wasteland. Right?
Like all of the inner planets, Mercury has taken a thrashing from impacts over it’s sad history. It skims around the sun pocked with craters. Some of these happen to sit right on the Mercurian Terminator. A terminator is not a killer robot with poor acting skills. A terminator is simply the demarcation where the planet’s daytime side meets the night time side.
This means that some of these craters contain regions draped permanently in shadow. Similar craters exist on our very own Moon, and yes, water ice has been observed in them! These ice filled craters are being touted as a bit of a sweetener for permanent human habitation on ol’ Luna.
Alas, Mercury doesn’t have much else going for it. It completely lacks a magnetic field, and lost whatever atmosphere it ever had long before Eukaryotes began crawling around.
Say you were an alien visitor to our solar system. Imagine yourself flying in: past the gas giants (what’s with that big red spot?), past all those pesky asteroids (that weird metal asteroid warrants a second look!), even past that blue green marble, with all the chatter pouring out on the electromagnetic spectrum. You keep on flying. It’s been a long flight, but there are two more planets to look at. This next one looks liks a big deal!
As you approach Sol 2 you’re thinking this place seems like Sol 3. Gravity is pretty similar , and it’s about the same size. There are even clouds here: lots of them!
Oh. It’s time to stop using your eyes and switch on some of that fantastic alien technology of yours.
Sol 2 isn’t so nice after all. In fact it’s downright awful. Some sort of disaster has befallen this planet. No magnetic field, atmospheric pressure that will crush your delicate little space gazelle should you ever choose to land and temperatures that can bake cakes.
There is water here though! Thick choking clouds of carbon dioxide and sulfur enshroud the planet, but there are traces of water in the atmosphere! It’s only 0.002 percent to be sure, but it’s there.
Your space gazelle (translation: extremely sleek and advanced spaceship) has beauty AND brains. Scans show hydrogen and oxygen ions trailing out behind the planet, and you realise that water loss is an ongoing issue for Sol 2. Solar winds have been slowly stripping Sol 2 of water for a long time; maybe billions of years, leaving this hellish dessicated planet behind. It’s a pity, you figure. Sol 2 would have been nice once. Sol 3 beckons as a potential home sometime, but the natives are barking mad. Looks like rolling in and blowing stuff up might be the only way after all. All that water!
Sol 3 has been studied to death, so you decide to swing around and take a look at the Red Planet.
Dry as a bone. Peaceful to be sure, but this planet is dead. Weighing in at roughly one third the size of Earth, Sol 4 may have struggled to hold onto any atmosphere it may have had.
Of course, being a little guy isn’t the be all and end all. Titan is the largest moon of Saturn. Somewhat smaller than Mars, yet fifty percent larger than our own moon, Titan sports an impressively thick atmosphere: thicker in fact than our own. Unfortunately Titan can be shunned from this article: it posesses oceans…..of liquid methane. No water here folks. I include Titan to demonstrate that smaller worlds can possess respectable atmospheres.
Mars, like Venus, is missing a key component here. Earth is the proverbial bowl of perfect porridge; just right. Many features of Earth are conducive to life, but perhaps one of the most important is the presence of an active core. This one feature prevents harmful cosmic rays from degrading DNA so badly that life mutates itself to death. It also prevents said rays from stripping away our water and atmosphere. This appears to have happened on Mars and it’s happening on Venus as we speak.
Does it, doesn’t it?
Mars is turning out to be a slippery customer. Evidence for erstwhile liquid water on the red planet seems to be piling up. It’s heading toward consensus that Mars once was much warmer and wetter than it is today.
NASA’s Curiosity rover is the closest we’ll get to visiting Mars for some time yet, and it has captured some pure Martian magic on it’s sojourns across the dead and lifeless face of possibly humanity’s first true stepping stone to the stars.
Possibly the greatest aspect of Curiosity is that it is a quintessentially human mission. Human eyes see the surface of Mars, beamed across vast distances and tease out information about this place. One simple photo can convey a lot if you know where to look and what to look for:
Essentially the general thrust of new discoveries these days is that it’s more likely for water to be somewhere than unlikely. I will end this blog post with new insights into water back here on Earth. As mentioned previously, several moons in the outer solar system are posited to possess vast quantities of water in the form of sub surface briny oceans.
However, it turns out Earth has a few surprises still up it’s sleeve. A diamond ejected around 90 million years ago from a volcano in Juina, Brazil contains imperfections, that, like a seemingly trivial clue in some glossy crime investigation show, point the way to to the one time existence of a subsurface ocean deep in earth’s crust. In fact, this ocean was (is?) posited to have descended nearly a third of the way to the edge of Earth’s core. These clues come in the form of hydroxyl ions, which normally only come from water. More evidence is arising, pointing toward water’s earlier appearance on Earth than expected. I will write about this and similar topics as I am able.
More posts on water in the solar system will be up as soon as I find time to write more. Keep on looking up! The Universe is there. See you next time, and thanks for reading.
Sometimes, science and a love for science begins with a story or two. I’ve always loved stories, be they in the form of books and movies. My favourite books of all time were C.S.Lewis’ Narnia Chronicles and Micheal Ende’s “The Neverending Story”.
What drew me into these particular stories so deeply was their references to cosmologies; to other realms and universes. For me the most alluring stories create not just intrigues and conflicts. I don’t really care about The Hero’s Journey, complete with it’s checklist of stages in a story. I don’t really care who’s the protagonist or antagonist. I care about the world these tales take place in. When I’m immersed in a story, I want to be immersed in the story. A universe, with all it’s history, is a key element of imagined worlds. To borrow a line from “The Dark Tower” by Stephen King:
“Beyond the reach of human range,
a drop of hell, a touch of strange. “
Again this tale was heavy with cosmology; alien yet familiar.
These stories were life changing for me in ways. They each provided pieces of a picture, of a universe I’d come to explore. The Narnia books were about other dimensions. “The Magician’s Nephew” featured travel between alternate realities. “The Neverending Story” showed us a universe created by imagination and perception. “The Dark Tower” was about a post apocalyptic world where the laws of space and time were unravelling, where the natural order of things was succumbing to a slow heat death.
But what about our own personal stories?
When I was a kid I spent a lot of time inside my head, visiting other worlds and other times. It was easy to imagine a beach as a coastline on some alien planet, or national park as some dinosaur infested part of Earth’s distant past.
The point I’m getting to here is that imagination and stories are important for science because they show us other worlds we’d like to explore.
But what about our own worlds and stories? As I’ve mentioned I spent a lot of my childhood immersed in imagination. If I couldn’t find someone else’s world….I’d provide my own.
I harp on about these other worlds, because the ability to imagine leads to the ability to ask questions. It enables you to speculate. It enables you to perform thought experiments..
An international mission to the outer solar system; the culmination of countless thousands of hours of diplomacy, frustration and determination finally reaches it’s goal.
A lone robotic probe has inserted itself into orbit over Europa. This moon has had the hearts of astrobiologists beating faster for a long time now. They’ve been curious about a global ocean ten times deeper than our own, lying beneath a cracked ghostly shell of ice. Oh yes, Europa could be the culmination of so many dreams..
The probe has been asleep on it’s long journey, stirring occasionally in the deep night to whisper to it’s masters. Digital murmours head home across a solar system filled with shrieks and moans: electromagnetic noise emitted by the planets themselves.
Who knows what the planets are saying?
The probe doesn’t care. It’s staring down at it’s new home. It fusses and frets, seperating and sending a lander down.
Vast sheets of rusty ice buckle and shift. The slumbering moon rolls in its sleep and a geyser of salty water erupts, pelting the lander with ocean spray as it prepares to land. Sensors coating the probe’s metallic hide taste the spray, sampling the alien cocktail for signs of life….
The moon is permanently encrusted in a shell of ice several kilometres thick. Below lies a deep salty ocean, warmed by constant tidal squeezing from Jupiter. This causes friction and tectonic stresses that render this moon a place of interest.
The probe takes a look around. The sky is eternally dark, and Europa is beholden to mighty Jupiter, which rolls and boils slowly across the night. Excited chatter from home has the probe going straight to work. Sophisticated AI takes over. Arms and legs extend and the probe stands. The days of ugly little rovers belong to antiquity now. Now a tall humanoid drone stumbles across endless Europan permafrost. Shattered ridges of glacial ice reach into the frozen sky like broken continental plates.
The drone walks. The drone sees. It picks up handfuls of snow. Sensors and chemical testing labs are woven throughout it’s frame; the very best nanotech taxpayer and corporate money can buy. The drone tastes the snow with it’s hands, looking for life. It’s masters believe it to be here.
Powder gently falls from the sky, leaving pock marks in the dark snow. There are organic molecules and precursors to life here. The drone tastes them. It looks for openings in the moons icy shell. If it can find a fissure it will climb down, until it reaches the watery underworld. Then, it will swim, exploring a place that up until now has only been a dream.
Then, it finds something unexpected.
A metallic gleam in loose shards of icy ejecta catch the drone’s eye…
The drone bends down and tastes tarnished copper. What is this?
The drone is not prepared for this.
It is programmed for the chaos of the real world: a state of the art descendant of the old survey/search and rescue bots. Protocol kicks in, and the drone dutifully sends images to it’s masters…
The machine is patient-as is it’s wont. It continues to explore the ice canyons and expanses of rusted ice. Life is here. The drone’s masters believe this fervently. Onboard mettalurgical analysis by the drone is now being carefully studied back home.
Back home the drone is all but forgotten. All attention is on the artifact it has found. Dutifully the drone sends back reams of data. Most of it is of incredible scientific value, but outside Mission Control no one is really noticing.
Instead, the world’s eyes are on a piece of the ancient world. Rome, to be exact. A speartip, broken away from it’s wooden haft, and buried in alien ice, 628 million kilometres from the Eternal City.