A comment on a facebook post I put up a few days ago got me thinking about habitability. Moreover, I got to thinking about the parameters of habitability.
We think that life here on earth is fragile, holding on to a thin silicate crust within a fairly narrow range of temperatures and conditions. For the most part it is. Life needs a fairly stable environment in order to keep on keeping on. However, there are plenty of examples of oddballs: extremophiles, that seem to do quite well in some pretty horrible places. The recent discovery of Antarctic microbes that derive energy from air itselfexpands the catalogue of organisms that could have analogues on other worlds.
Now, extremophiles do well in extreme environments. No brainer there, and there is no shortage of extreme environments in our solar system alone.
Venus is an example, and a good one. Analogous to Earth in size, density, gravity and composition, it differs markedly in others. No magnetic field, no water (at 0.002% of the atmosphere not worth mentioning), surface temperatures that melt lead, and atmospheric pressure ninety two times what we’re used to here. It’s horrible.
No plate tectonics. On earth we slowly sail about the globe on slabs of continental crust, which happen to be more buoyant than the thicker, denser oceanic crust. Driven by convection of magma in the mantle, crust is slowly pushed hither and thither by tectonic processes such as seafloor spreading.
To understand what this is, imagine a pot of something thick like soup or porridge on a stove top. As the contents of the pot heat up they begin to stir. Have you ever noticed when this begins to happen that as the surface begins bubbling the top layer is forced aside as new material wells up from below? This is seafloor spreading in a nutshell. Magma from within the earth wells up, heated by a radioactive core, and pushes the seafloor aside as it breaks through, forming new crust. The continental plates, perched atop this moving crust, slowly journey across the planet.
Why is this so important to life on Earth? Because our planets interior is so hot, plate tectonics (along with volcanism) is the primary means by which excess heat is released over time. If this didn’t happen, well, you wouldn’t be here reading this and there would be two Venuses in our solar system instead of one.
For reasons unknown, Venus shut down. It’s core stopped spinning, it’s magnetic field dwindled to nothing and radiation from the sun began a process of stripping the planet of water. Water is a true miracle ingredient. Not only is it a solvent for biological processes, it’s also a lubricant for plate tectonics. Venus seized up and overheated: exactly like a car without oil will do.
A stagnant lid world is one which has no plate tectonics. Climate is seriously affected by such a situation. With no means of escape, heat builds up within, and eventually it becomes an exo-Venus: scorching hot.
Researchers looking at the issue of habitability on exoplanets have looked at the implications of a stagnant lid regime for the possibility of life. Whilst it would obviously be different to life on earth, other factors can lend habitability to a planet.
These other possibilities are exciting indeed. I’ve been exploring astrobiology through images, producing a bunch of pictures. They will be appearing over the next few posts, so I hope you enjoy them. They’re doing well on Instagram!
Thank you for reading the ramblings of a space nerd. The universe is just too intetesting to ignore.
Hey all. I’m finally excited about something for the first time in awhile. I recently received a tablet from my LOVELY wife. It’s a Wacom Intuos Pro. I have been wanting an art tablet for years now. I had one once, but it was a slow, crappy little thing on slow crappy little computers. This one is a bit more high end.
This thing has opened up creaking doors in my brain, which I thought had fused shut. It’s even been helping me in a therapeutic sense. I have had some pretty dark years recently, and they have taken their toll. This tablet has enabled my mind to properly elucidate and crystallise several things which have been weighing me down…
Sometimes art can give a form to nameless and shapeless fears. It can help you contain and control them, by capturing them on paper (so to speak)…
This tablet is already hard at work, helping me with my next video, which takes a look at how a quaint little engine from the nineteenth century could help us take a real look at the surface of Venus!
Lots of things sloshing around in my head! The video is shaping up to be a lot of fun! I hope you can check it out when it’s up! I will start putting up artwork as it comes. Here’s the thumbnail for the video..What do you think?
Find me on my facebook group, where astrobiology is the name of the game!
Hi all. It’s been a while I’m ashamed to admit. I’ve been working on a new Facebook group to raise the profile of my channel. It’s been fun. Here is the link (hint: join the group!)
Here is my newest video. A basic breakdown of what exactly the Goldilocks (or circumstellar habitable) zone is, and it’s importance to life on Earth. If you like the channel please subscribe!
I’ve also provided the script/transcript for my upcoming episode of “Astro-Biological:”, which introduces us to the concept of the Goldilocks Zone….
G’day! Welcome to Astro-biological:!
Ben what the heck are you talking about? What’s the connection?
Let’s go check out THE GOLDILOCKS ZONE!!!!
Life, as I like to remind you, is really special. Here on earth, life exists only because certain conditions are met. Today, we’ll consider water. Everything needs it, but it only exists as a liquid at the surface here on Earth.
So? Big deal right?
Well it is actually!
Check out the sun. Giver of life! Driver of climate! Pumping out some pretty respectable energy. How much?
1 yottawatt equals 10 with 26 zeroes after it!
Brutal! And the sun is a pretty average star! Nothing special about it!So there’s plenty of sunlight for everyone!
Could other planets benefit from the sun’s golden goodness the way we do? Let’s take a look at the inner planets. They’re the only ones that really matter in all this…
Let’s see…Mercury, Venus, Earth and Mars. The rocky planets. The so called “Terrestrial Planets”.
Mercury is 58 million kilometres from the sun. That’s really close. This close proximity has turned Mercury’s surface into an oven, where liquid water couldn’t possibly last.
Let’s visit the next in line: Venus. Venus is similar to Earth in composition, gravity and size. Long ago Venus might have had oceans just like Earth, but again the planets closeness to the sun and other factors saw all that water disappear into space. Venus is now the hottest place in the solar system. Definitely no liquid water there anymore!
Wanna know more about what happened to Earth’s twin? This guy I know made a video!
Earth! Beautiful Earth. Our home. Every thing’s home actually. Eighty per cent of earth’s surface is covered by liquid water. There’s so much spare water here that our bodies are mostly made up of it! It’s absolutely everywhere, even locked up deep in the earth’s crust! Enough of earth. We’ve all been there.
Next planet out:
Mars. The cool planet. Every one wants to go here. Pity it’s so cold! Liquid water may exist here in tiny amounts, but most of the red planet’s water is locked up as ice or permafrost just below it’s surface. Plenty there for future colonists to use, but nothing readily available for biological processes. Pity. It’s a beautiful planet. Just ask Matt Damon!
So what is the Goldilocks Zone then?
Here’s the inner solar system. Mercury, Venus, Earth and Mars. Let’s visit a special guest who can explain the Goldilocks Zone for us…
ChefBenbit. (Watch the video when it’s up!)
Nice work Chef! So, if Earth was a bowl of porridge it would be the one Goldilocks ate: the one that was just right! it’s that simple! Earth is lucky enough to be at the perfect distance from the sun, where water likes to slosh around in liquid form. Things would be a lot different here if that wasn’t the case.
So that’s it for now! A simple but important piece of information. The Goldilocks Zone!
How am I going so far?
If you thought I was alright, then subscribe for more. If you thought this video was useful to you, then give it a like! Likes help this channel get noticed. That little notifications bell is just the thing if you want to see more. Go on. You know you want to.
Thanks for watching astrobiological. Giving you the universe in plain human. Ciao!
You’ve seen Mars. Who hasn’t? Done to death! Orbital skydiving from Phobos? Yesterday’s thrill! Jupiter? Saturn?
Deep sea diving with the natives on Europa?
Chuck all those snoozefests in the trash because we have something special just for the first 10 callers!
Yessiree we’ve moved on from plain old space tourism. None of this flying over the dark side of the moon for hyper rich tourists! Its 2087, and for a limited time Ben’s Lab Mystery Tours have a ripper for you!
For a moment I thought I actually heard crickets chirping in this studio…
What’s that you say? Venus is the Florida of the Solar System! How can that possibly be exciting? I don’t want to fall asleep in the upper atmosphere, enjoying the sun and mild temperatures on some Cloud City! Retirement villages, man!
Well, how about we forget the cloud cities then? We have put together- for the extreme extreme sports nuts out there, a holiday from Hell- in Hell!
Take a walk on Venus.
I hear your bowels clenching. Good!
Venus is hardcore. Venus wants to eat you alive and spit you out! Did you know our ancestors thought Venus was a beacon of serenity, drifting peacefully in the heavens. Ha! They thought Venus was a cloud covered blue green marble like our little planet.
Well, they were right. They just had bad timing. Earth and Venus formed at roughly the same time, forming from a molecular cloud, made of gas, dust and other muck drifting around our own newly formed sun.
Earth got lucky. We were at just the right distance from the sun for water to exist in a liquid state on the surface. Venus is just within this little strip of safety, called the Goldilocks Zone.
For half a billion years or so, Earth had a real twin. Sure, Venus is pretty much the same size as Earth, with almost identical gravity, but those two things do not a paradise make. What Venus had back then was oceans. Continents even. Venus kind of looked like Earth!
Am I selling it yet! Sounds pretty sleepy, doesn’t it? If you nutcases can’t handle the peace and quiet go stick your head in a volcano on Io.
Call now! This is a once in a lifetime experience!
I have a caller! Let’s see who it is!
Jasper Dixon wants to know; what happened to Venus then? How did an earthlike planet transform into an inferno, with crushing clouds of sulphuric acid and carbon dioxide? What about that atmospheric pressure, 92 times our own!
I agree Jasper. That’s just plain silly. Well at the risk of driving away listeners I’m going to tell you. If I explain why Venus is the nastiest place in the solar system I reckon the phones will be ringing off the hook!
It’s all about water. Back on Earth water isn’t just used to make fizzy drinks and fill swimming pools. It isn’t just necessary for all life. The planet needs water as well. Really!
I know, I know, the planet has a hydrological cycle. Oceans are vast heat sinks, storing heat and influencing climate. Water evaporates, creating rain and clouds, which not only bug us when we’ve just hung clothes on the line, they also reflect a lot of sunlight and heat back out into space. The planet’s reflectivity is called it’s albedo.
This is all true and all very important. But water performs one other vital function:
It lubricates the planet.
Long ago Earth looked like this.
Some time later it looked like this.
Plate tectonics, my friends. The continents are basically slabs of crust which happen to be less dense than the crust the ocean floor is made of, and so they float and slide around, moving very slowly, but definitely moving. Australia is whipping along at breakneck speed: at about fivecentimetres a year!
Plate tectonics and other events in the earth’s crust perform an important task; They release heat from the planet’s core. This planet contains a liquid metal core which is kept superheated by the decay of radioactive elements left over from earth’s formation. If the planet’s crust didn’t fracture and split all the time where would all this heat go?
Nowhere of course! The planet would just heat up and heat up, overheating until it became, well, it became Venus. We don’t want that.
So what the heck does water have to do with this! We don’t care anymore! We get it! Shut up and take our money!
Impatient lot, aren’t you? Well, you can’t hurry education!
Remember those cars the old timers used to drive around? Remember how they had to put oil in them to stop the engines seizing up? Well, if earth’s crust isn’t kept lubricated by vast amounts of water running deep, then it too will seize up. This is what has happened to Venus.
Partly, at least. The planet’s surface is now so hot as a result of this runaway negative feedback that it can melt lead.
Better make sure you pack a decent space suit, extreme sports fans. One that can handle temperatures of 490 degrees Celsius. Make sure the electronics are tough too. It was only due to the advent of electronics that could operate in these temperatures that rovers and eventually humans were able to reach down and touch the Venusian dirt.
All you rugged outdoorsey types: don’t bring compasses. Yes, it’s a great idea, no they won’t work. Period. Venus has practically no magnetic field. This is a side effect of it’s core shutting down long ago. Don’t even ask me why. It may be 2087, but how the heck would I know? I’m selling holidays, not winning the Nobel Prize.
The folks up in those cloud cities have it pretty good. Sure, hard core acid rain is a pain, and having to wear oxygen masks can be annoying. By and large, however it was a brilliant idea. Much easier than that whole Mars fiasco back in the 2050s. Terraforming a whole planet? Good luck! See you in a couple of thousand years. Maybe. But those cloudies have no idea what’s below them. I know it’s not pretty.
Not a drop of water anywhere. A few wisps in the atmosphere. 0.002 percent of it is water vapour I think. Down on the freshly formed lava plains (by fresh read: less than 100 million years old!) though; nada. Zilch.
Venus is close to the sun. A lot closer than earth at 108 million k’s. The Sun, being the vicious ball of fury it is, is constantly punishing the inner planets with solar radiation. Mercury is completely dead, baked clean by its proximity to the Sun. Venus held onto to atmosphere for a while, but when it’s core bit the dust that’s when things went south.
Earth has a magnetic field, which protects life on earth from harmful cosmic and solar rays. Sure, we get sunburn sometimes, but that’s a damned sight better than being baked to death, or having our DNA so damaged by radiation all life would perish from lethal mutations.
Without a magnetic field Venus’s one time oceans were slowly stripped and cast into space. Even today traces of this water are being ripped away by solar rays and sent into the Big Empty.
Still sound like fun? There’s always some hardcase out there who just can’t listen to good sense.
Operators are standing by!
One other thing. Feel free to call in and let me know exactly what happened to Venus’s core…
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.