Tag Archives: subsurface ocean

Beyond the Pale Blue Dot

In all the gin joints, in all the world…

An old movie line, but it speaks a truth: life is miraculous to the point of being impossible. We search for it. To be fair, we’ve really only begun looking seriously in the last thirty years or so. The discovery of the first confirmed exoplanet in 1995 propelled us into the heavens, and we began to seriously believe we may just find life out there. Why not? That isn’t a scientific response, but life is incredibly improbable. The amount of unbelievable coincidences that enabled life to appear on our blue green marble almost beggars belief. Everything had to be just right, or life just never would have happened. Just like the proverbial bowl of porridge, which actually leads to the topic of this post. A certain famous little girl of fairy tale fame lent her name to the region around a star at which liquid water can exist in a stable form on the surface. More precisely, this region, or “Goldilocks Zone” is the distance from a star: the sweet spot where liquid water exists. To be more precise again, the Goldilocks zone is a function of stellar luminosity and output. The more energetic a star, the further out it’s Goldilocks or habitable zone is. It’s a fairly linear progression: the hotter the star, the more distant it’s habitable zone. Image: NASA/JPL Extremely simplistic, but that’s us in a nutshell. We happen to be just the right distance from our sun. Because life has only been found here (as far as we’re aware), we naturally think that life will tend to favour “earthlike” conditions somewhere else. That probably makes some sense. However, does all life in the universe necessarily exist on a rocky, watery world that essentially mirrors our own? It doesn’t have to be the case. Much recent thinking has been directed towards redefining the habitable zone. Our solar system is one of countless billions estimated to exist in our galaxy alone. As researchers discover more exo-solar systems seemingly every day it’s becoming apparent that perhaps our particular corner of the block is actually quite unusual. For astrobiology to have any relevance at all it’s important to think outside the square. For that reason we take a look at the habitable zone as we know it and stretch it’s limits.

The Local.

In our solar system we see a complex family of objects, all held together loosely by gravity. Many of these planets are suspected to possess water. Lots of it. In fact it’s believed by many researchers that the amount of water in the solar system not situated on earth is quite large. Our blue green marble is actually fairly arid compared to many other worlds in our solar system. The Galilean moon Europa is smaller than earth’s moon, but may hide two to three times more water than is found here! Earth is surprisingly dry compared to tiny worlds such as Europa, with the blue orbs representing an approximate comparison of each world’s respective water content. Europa is one of a small group of worlds in the solar system that have piqued the interest of astrobiologists over the years, as they are believed to possess certain sets of conditions and environments that could be conducive to the presence of life. Not just habitability (as was possibly the case with our Moon), but abiogenesis. Life arising from whatever hidden firmament lies within their icy depths. The reason these worlds give astrobiologists hope is that (quite naturally) exo-solar systems come in all shapes, sizes and flavours. Moons like Europa, Enceladus, or even now quite dead worlds such as Venus and Mars throw us tantalising glimmers of hope that Earth based life is not alone in the universe. These worlds (and others we discover) often possess sets of conditions assumed to be completely hostile to life: as we know it. However, even life as we know it has shown us that it can really go off script sometimes. Whole new classes of extremophilic organisms have been discovered, and are still being uncovered in some really nasty corners of the world which show one thing: life’s ability to shuffle pieces around on the evolutionary chessboard has enabled it to live almost anywhere: in space, nuclear reactors, and the earth’s mantle. Bacteria have recently been discovered in Antarctica which literally use hydrogen as a food source! These organisms suggest that the traditional concept of a habitable zone: the right amount of heat, light and atmospheric pressure as we observe on earth need not necessarily apply to alien planets.

Tidally locked exoplanets

These are worlds which orbit their star(s) with one side permanently facing inward. The obvious ramifications of this: the side facing the star obviously has a much greater actinic flux than the planets night side. Translation: it is likely a scorched wasteland, where temperatures are oven-like. On the dark side we expect to find extremes of temperature at the opposite end of the scale. This side would be frozen and permanently dark. Overall, the planet doesn’t seem to hold much hope for life. It is believed that a good percentage of confirmed explanets are locked into tight orbits around their stars. Often these worlds take a few days (or less) to complete an orbit, and they are most likely tidally locked as a result. But all hope is not lost. The discovery of water ice in permanently shadowed craters on worlds as hostile as mercury and the moon leads many researchers to believe similar regions could exist on tidally locked exoplanets. Such water filled craters lie within the Terminator, the boundary between a planets day and night side. On a larger object such as an exoplanet, small strips of habitability could exist, situated in literally a permanent twilight zone. Twilight Zones of habitability could be a surprising spot for life to appear… In such a situation, the habitable zone as we define it would not be as dependant on distance from a star.

No Habitable Zone?

The recent discovery of two rogue planets lends itself to another interesting scenario. These rogue worlds are planets which aren’t gravitationally bound to a solar system. They are believed to be quite common. Current estimates have the complement of wandering worlds in the milky way galaxy at approximately two billion. How could such exotic locations possibly host life? Because geothermal or tidal heating could provide conditions in which life could possibly eke out a niche. Tidal heating is a mechanism for internal heating which has been observed in several frozen, distant worlds in our own solar system. Europa (mentioned above) and Enceladus likely possess subsurface oceans of liquid briny water. The heating for this comes from the gravitational stresses caused by interactions with nearby worlds. In the case of Europa and Enceladus their elliptical orbits around Jupiter and Saturn respectively cause an ebb and flow of tidal flexing in their rocky cores. Such frictional heating may even give rise to fissures and hydrothermal vents providing possible locales for biogenesis, as may have been the case here on earth. These frozen worlds appear lifeless, but appearances could be deceiving. Whilst far beyond the habitable zone of this solar system, the presence of life on either world would lead to further redefinition of habitable zones. Exoplanets are believed to number in the trillions in this galaxy and the recent discovery of the first known exomoon suggests that moons could be even more numerous. After all, in our solar system moons and natural satellites outnumber the planets by ten to one. Habitability on any of these worlds opens up the options for researchers observing distant solar systems for signs of life.

To the Weird..

Last but definitely not least. A benchmark of habitability as we define it for earth based life is that, overall, the environment should be fairly benign in order for life to have a chance. Earth itself only became habitable after billions of years of incredible geological upheaval and intense bombardment from outer space. Not only that, the presence of a thick atmosphere afforded protection from cosmic rays pumped out by a young sun. A class of exoplanets known as super earthsmay be able to support life despite often being in orbit around extremely energetic stars such as red dwarfs. These stars are tiny, often having only ten percent of the mass of our sun, but they are nasty. Frequently they have been seen producing extreme solar flare activity. This image shows a solar flare being generated by the red dwarf star DG Canum Vernaticorum (DG CVn). To put it in perspective the most powerful solar flare observed on our sun was rated X45 on a standard scale used to gauge glare events. In comparison DG CVn was rated X100,000: 10,000 times more powerful! At its peak the DG CVn flare reached temperatures 12 times hotter than the core of the sun! NASAs SWIFT observed this event over 11 days, recording the most powerful flare ever recorded. Image: NASA/SWIFT It stands to reason that any nearby planets would be baked into oblivion by the levels of energy being produced during such events. But larger rocky worlds such as super earths could provide a slim chance of life. Super earths are rocky worlds ranging in size from three to five times larger than Earth. Their mantle and outer layers could act as a shield against radiation, enabling any lifeforms present to carry on in subsurface biospheres, akin to recently discovered microbial biospheres deep in the earth’s crust. Lifeless surfaces could hide thriving ecosystems throughout the galaxy, or even beyond. Even neutron stars could harbour life bearing worlds if conditions are just right. These stellar objects don’t seem like an ideal location for life, but again a suitably large and dense world could provide safe harbour against lethal X-rays and other electromagnetic nastiness. Small worlds could be destroyed if they strayed too close, but if a super earth lay at a safe distance, who knows?

A Final Thought….

In this overview it’s been shown that life can theoretically exist outside the traditional confines imposed by earth based habitability criteria. However, I’ve only looked at planet based life… Who knows what else is out there? That’s a whole new type of thinking. Thanks for reading! I have a new video coming, which will be based upon this blog post. In the meantime, here are some speculations on a habitable moon in the distant past. P. S.. I have recently set up an online store, featuring my designs on a range of products, any of which would make fantastic and unique gifts! Take a look: https://www.redbubble.com/people/AstroBiological?asc=u All images © AstroAF Designs unless specified in image caption.
Advertisements

The Lost Moon

Boom. Image: Ben Roberts

The moon is one thing we all have in common. I’ve always loved looking up at it. Whether it’s from a religious, mythological or scientific perspective, Luna holds a powerful mystique regardless. The story of the moon is written into the story of life itself.

What does the colossal impact taking place in the above picture have to do with the moon? Because it’s likely the moon formed via a process of accretion.

Around four and a half billion years ago, earth itself had only just coalesced from a cloud of gases and dust that eventually gave rise to the entire system.

Image: Ben Roberts

Earth is believed to have formed without a moon. In fact earth as we know it today formed as a result of the moon.

Picture this. Earth is newly formed. It’s a toxic planet with vast tracts of it’s surface covered by a magma ocean.

Image: Ben Roberts

From the outer solar system it comes. An object roughly the size of mars slams into Earth 1.0. The object has been named Theia. This impact is catastrophic, essentially tearing away the outer surface of our world.

Image: Ben Roberts

Where does all of this crust go? Into space, forming a ring around the newly resurfaced earth. It is this ring, consisting of the fragmentary remains of both our world and Theia, that will accrete to form the moon.

That’s the moon in a nutshell. It’s influence on the course of life has been fundamental, with a critical role in climate and seasonality via the key role it plays in tides. For over four billion years the moon has stared down upon the world, seeing the march of life with all of it’s ups and downs.

Has the moon itself been lifeless all this time? It’s been our closest neighbour for practically forever. We have always thought of the moon as a dead, hostile place. Today it certainly is. With no atmosphere to speak of, negligible water and lethal solar radiation bombarding it’s surface, the consensus of opinion is that the moon is completely devoid of life.

Image Credit: NASA/GSFC/Arizona State University

But it may not always have been like this.

It may be a stretch, but several studies have suggested that at least for a time the moon may have been at least habitable. Perhaps not an oasis of life, but a place that could harbour it.

The moon may not quite have looked like this, but volcanic activity (seen on the limb) would definitely have contributed atmosphere. Images: Ben Roberts

How is this viable? As noted, we all know the moon is hostile to all life. However, the moon is now an inert world, devoid of any geological activity.

Once, though, the moon was anything but inactive. In the period after the moons formation, around four billion years ago it was highly volcanically active.

A habitable moon more likely looked something like this. Image: Ben Roberts

Intense volcanism can be a source of atmospheric gases. This is definitely a factor on earth. Many atmospheric gases, including several trace greenhouse gases are pumped into our skies by volcanoes. Greenhouse gases are pivotal in regulating climate on earth. On the moon all those billions of years ago, volcanoes may have done something similar, bulking up the lunar atmosphere and enabling this tiny world to retain some heat. In addition, a thick atmosphere provided protection against solar radiation and an environment amenable to liquid water. Water is, as we know, crucial to all life on earth. “Follow the water” is one of the central catch cries of astrobiology. Find water, the reasoning goes, and life may be there.

This isn’t always the case though. Water exists almost everywhere in the solar system. There is even water vapour on the sun! There is plenty of water on the moon, locked up as ice in several craters in permanent darkness.

How would all this water have arrived on the moon? Prevailing theory regarding the origins of earth’s water held that much of it was delivered by cometary impacts. This is certainly reasonable. Recent discoveries though hint at vast reservoirs of water locked up deep within the planet itself. Water may be replenished over the eons by outgassing from volcanoes for example. This could have happened on the moon. Several studies of lunar composition have demonstrated that there may be similarly vast amounts of water locked up within the moons core. The ancient moon may have gained a thick watery atmosphere from centuries of volcanic activity partially terraforming it.

So, to put a long story short, water by itself is no guarantee of habitability. The moon, however, may once have been a very different place. With a thick atmosphere providing protection from cosmic rays and allowing pools of liquid water to form, life could have quite easily gained a foothold there. Most likely this life was in the form of unicellular organisms which may have arrived via lithopanspermia. This is a process whereby worlds at close proximity can exchange life or it’s building blocks via impact or volcanic ejecta.

Lithopanspermia: is it a thing? Image: Ben Roberts

This very concept is being applied to crowded systems of exoplanets such as the TRAPPIST-1 system, and is an exciting avenue to explore. In such a system, the possibility of interplanetary ecosystems could exist! This is, of course, very theoretical, but damn what an interesting idea!

What do you think? Was the moon ever habitable?

While you’re at it, check out my tiny little YouTube channel, giving you the universe in plain human!

Sailed the Ocean Blue

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.

A water world with a thick atmosphere of steam.

For now, we have only our imaginations with which to explore these worlds…

An aerial view of remote coastline on a hypothetical watery exoplanet.

A new video!

Translations

More images.

I’ve been thinking some of these may look good as posters. Thoughts anyone? They provide another way to reach people, as I myself continue to explore and learn about a truly incredible topic.

I like the look and think my channel will finally benefit from a coherent look and vibe. The retro font works for me, and the surreal, fantastic feel of the pictures is my jam.

Channel News

A new video exploring the possibility of directly imaging exoplanets is coming very soon!

Here is a snippet; sans sound or effects just yet!

More coming.

Water, water everywhere

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.

Earth

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.

0.006 percent!

wp-1486533871225.jpeg

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.

The Sun

20140326_171046.jpg
Huh?

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.

wp-1486534460971.gif

Mercury

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?

2017-02-02-1.png
462 degrees in the shade.

Wrong.

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.

wp-1486534410711.jpeg
Similar shadow filled craters have been observed on the Moon.

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!

Venus

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!

wp-1486534727172.jpeg
Venus was once…almost idyllic?

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.

wp-1486534821149.jpeg

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.

Mars

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.

With 15% of Earth’s gravity and temperatures at an extremely frosty -176 degrees Kelvin, Titan is not a viable destination for human exploration just now. But it is more similar to Earth than anywhere else in the solar system…It just doesn’t have any water.

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.

Another Eden?

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.

Our descendants may one day take off their helmets and breathe Martian air.

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:

img_20161221_151551.jpg
These are synaerisis cracks. They typically form in river or lake beds when water dries up, leaving the mud to crack as it shrinks in this fashion. Whats so special about these cracks? They’re on Mars.

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.

earth-iss-image.jpg.jpeg

Ben’s Lab.