Tag Archives: water

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!

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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!

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!

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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

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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.

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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?

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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.

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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!

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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.

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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:

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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.

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Ben’s Lab.