It’s been estimated that a good percentage of planets beyond our solar system may be water worlds.
We here on mother Earth like to think of our blue green marble as a water world. Indeed it is watery, and water is pretty much the reason anything lives here at all. That’s why astrobiologists naturally seek signs of water on exoplanets. “Follow the Water” is a central tenet in the search for extraterrestrial life.
But compared to some worlds, earth really isn’t that waterlogged at all. It’s 0.002 percent water by mass. Only a tiny fraction of that water is available to terrestrial life. That water which isn’t directly involved in biological processes is linked to them, linking life to the planet via seasons and climate.
Some exoplanets are believed to be up to fifty percent water! These are true ocean worlds. To date, up to thirty five percent of exoplanets larger than may be covered by vast layers of water that may or may not harbour life. The jury is well out on that, but the idea is intriguing (and tempting) as the traditional definition of habitable zones is being stretched and reinterpreted.
For now, we have only our imaginations with which to explore these worlds…
The universe is turning out to be a more interesting place with each passing day for me. It’s not all about reading research articles and trawling the internet for interesting news in the vast field that is astrobiology.
I’ve been working on images related to various themes in astrobiology. This field really is a playground for the imagination, and it has something for everyone….
Something really special here: possible traces of limestones found in the fragments of objects orbiting a nearby white dwarf star…
Differing definitions of the Habitable Zone further push the limits of life in the universe..
Svante Arhenius, a swedish chemist and early pioneer of the theory of panspermia..
Ruminations on the code (codes?) that make life possible. How many languages does life have in the Universe?
Does the chemical rich, pitch black seabed of Europa host life? Does that of Enceladus?
The first image I created. I hope you’ve like these. There will be more! By the way, the background for this image comes from an online simulator called Goldilocks, by Jan Willem Tulp. His work can be found here. It’s really cool.
If anyone has read “The Hitchhiker’s Guide to the Galaxy” quadrilogy they would have been struck by some of the big ideas hidden within Douglas Adams’ deadpan humour. One of the heavy concepts that stuck with me was the idea of planet building. According to the story, Earth as we know it today is a planet sized super computer, built to perform one task: to figure out the meaning of life. A planetary architect named Slartibartfast is entrusted with overseeing the rebuild of Earth after it’s destroyed due to a galactic scale clerical error.
Possible? Why not? According to prevailing theories, planets mainly form via the process of accretion. Simply put, particulate matter adrift in molecular clouds clumps under the inexorable pull of gravity, forming ever larger clumps that clump to ever larger clumps and so on. Eventually a planet or star is the inevitable result.
Why couldn’t this be done artificially? Would it be even possible? If it’s just a matter of throwing lumps of crud at other lumps of crud and hoping they stick, then why couldn’t it be?
It’s the future. Humanity lives and works in space. The asteroid belt is the new frontier or wild west. Chunks of formerly useless rock are now homesteads or villages. Distances are not overly tyrannical. An asteroid is typically only a few light seconds from another. However, asteroids can be moved. Bigger asteroids like Ceres, Vesta or Eros would comprise the main hubs of commerce and trade in this new world.
Smaller settlements such as these “homesteads” could make life easier for themselves in terms of travel times (and therefore fuel costs) to larger, more important settlements by moving closer. In the frictionless, zero gravity environment that is space this wouldn’t be too technically difficult.
Time has moved on. The asteroid belt is a thriving collective of trade networks and conglomerates of smaller settlements. Smaller asteroids now cluster around larger ones like space junk in low earth orbit. Economically, this proximity is making things easier for everyone, and lots of people are getting rich.
Just imagine though if humans disappeared. The zombie apocalypse hit outer space and spread to all corners of the solar system.
(That’s the fun explanation)
Every living human is gone, and the asteroid belt is now a vast ghost band, forming a wreath around the sun, somewhere between Mars and Jupiter. There are all these swarms of asteroids now adrift, all artificially brought closer together by generations of enterprising human beings No course corrections keep them from colliding and so many of them are doing just that. Orbits decay, and tiny chondrite specks plough slowly into larger planetesimals.
See where I’m going with this? Over time, natural accretion would naturally lead to planets forming, or at least a large moon sized object. In millions of years the solar system could have a tenth planet (let’s just sneak Pluto back into the club. Don’t tell anyone!)
Planet Building! Essentially a garbage planet could form from the artificially placed asteroids and other objects now in very close proximity and drawn by the slow but inescapable pull of gravity.
I think it’s an exciting idea: a real megastructure! The ultimate megastructure!
This post was inspired by a chance statement in a video discussing space colonies on Isaac Arthur’s Science and Futurism youtube channel. Check it out. Isaac has a huge catalogue of lengthy discussions on some really interesting concepts. Here is a link to the relevant video if you’re interested:
Last but not least, here are links to the social media for Maciej Rebisz, the talented artist behind some fantastic space artwork, including the asteroid colony about halfway down the post.
My newest video features the bizarre metal asteroid 16 Psyche. This improbable chunk of iron and nickel may one day be mined, yielding metals worth over 10000 quadrillion dollars! No, that figure doesn’t seem real to me either.
Here is the transcript for said episode. I had some fun experimenting with effects for this episode, and I think it works well!
“G’day metal heads!
Do you think you’re rough and tough?
Do you believe you’re made of metal?
See if you can outmetal THIS monster! A ball of metal mayhem 200 km across! Let’s go check out 16 Psyche!!!
Long long ago, in a molecular cloud not so far away….
The Solar System: Episode 1
It is a time of turmoil in the newly formed solar system. Planets, moons and other heavenly bodies have coalesced from the primordial cloud. As larger bodies fall into orbit around a blazing new sun, smaller worlds are caught up in a system wide spree of destruction known as the Late Heavy Bombardment.
It is a perilous time for a planetesimal or moon, and many smaller planets are destroyed in the cataclysm.
A lone youtuber known as Ben has ventured out into the Big Empty, to visit the long dead core of one such world. Upon reaching it, he sends in a gallant drone to investigate….
Yes Sir! Here we are. Welcome to 16 Psyche. An oddball world really. This place is special for a few reasons.
Discovered in 1852 by the Italian astronomer Annibale de Gasparis, 16 Psyche was named after Psyche, a figure from ancient Greek mythology. The word itself means “Soul”.
16 Psyche is pretty big: a ball of metal over 200 km in diameter! It’s almost entirely nickel and iron to be more precise, although about 10 percent of its surface is strewn with silicate rock much as you’d find here on good old earth.
So this ball of tinfoil from hell comprises nearly one per cent of the mass within the asteroid belt where it lives. It actually lies roughly halfway between Jupiter and Mars, about 3.3 AU from the sun.
What’s an AU?
AU is a very common astronomical term. It means “astronomical unit’. 1 astronomical unit is defined as the distance between Earth and the Sun. This is about 93 million miles or 150 million kilometres. At 3.3 AU this means 16 Psyche lies some 308 million kilometres from the Sun.
Wanna know what’s really special about this metal asteroid?
First of all, 16 Psyche is extremely valuable. All of that iron and nickel within has been valued at over 10000 quadrillion dollars!
Obviously that means a lot of folks would love to mine it for all that metal. A whole bunch of companies have sprung up in the last few years, looking to cash in on asteroids: the next big thing!
Personally, I don’t care about all that. You wanna know what’s really cool about 16 Psyche?
It’s the exposed core of a long dead protoplanet; the remains of a tiny world maybe 500 km in diameter. This tiny planetoid took a beating during the Late Heavy Bombardment, some 4 billion years ago. In fact, this nameless world may have been impacted by other large bodies up to 8 times. This pounding shattered the outer crust, sending scattered fragments out into the newly forming asteroid belt and leaving behind an exposed core. Scientists would love to study 16 Psyche, because it can teach us a lot about planet formation and how planets work- including our own.
Just look at it! Imagine walking on the core of a planet. 16 Psyche gives us an opportunity to see into our own world in a way. It’s like a time capsule: a snapshot of a newly forming planet, frozen in time for ever.
This is the real value of 16 Psyche, this frozen soul. Let’s take one last look and imagine actually being there….
I hope you’ve enjoyed watching this episode. It was super fun to make, and if you got something out of it, then subscribe to this channel for more. Join the astrobiological Facebook group, find me on Twitter. Links in the description.
AstroBiological: giving you the universe in plain human. See you next time!”
I’ve been absent for a couple of weeks, working on a new Facebook group devoted to Astrobiology. So far it’s been fun, and people are responding to it. It’s not massive but there’s definitely a level of engagement which I’m enjoying. Hopefully others are enjoying it too!
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: