The origin of Earth’s water is still something of an open debate. The popular theory at the moment is that the primordial Earth was far too hot to contain any form of liquid water, its molten surface still reeling from the cataclysmic events that led to its creation. However others postulate that the water was trapped deep below the surface, only to arise later on as the Earth cooled and an atmosphere developed. It’s an interesting question not only because of how fundamental water is to life but also because we seem to have a lot more of it than any other planet in the solar system. Thus the question of where it came from, and why it’s managed to stick around for so long, is one of continuous scientific enquiry, including such missions as the recently celebrated Rosetta probe.
If we run with the theory that Earth’s water came from some extraplanetary source then the question turns to what the original source might be. Comets seem like a good candidate as they’re primarily water ice by composition and were far more common during the early stages of Earth’s life than they are now. However measurements of isotopes within water of several comets, including Halley, Hyakutake and Hale-Bopp has shown that they are not likely the primary source of water that’s currently on Earth’s surface. The composition of water found on asteroids and other water formed minerals on the Moon seem to indicate that a source closer to home is far more likely which Rosetta’s latest data appears to confirm.
The comet that Rosetta was investigating, the romantically named 67P/Churyumov–Gerasimenko, has a ratio of isotopes that is completely different to anything that’s seen on Earth. The reason that this is important is due to it’s orbit as 67P is what we call a Jupiter class comet, a collection of various comets that have orbits that don’t extend far past Jupiter. It was thought that these kinds of comets would have been more likely to have been involved in the creation of Earth’s oceans than comets from further out, due to their proximity. However 67P, with its wildly different composition to Earth (and even other bodies in the same vicinity), lends credence to the idea that comets aren’t the likely source of Earth’s oceans. Indeed it’s far more likely that water and minerals trapped in asteroids are the likely source, based on how similar their composition is.
Now this doesn’t rule out comets completely as there’s potential for further out Kuiper belt class comets to have the composition we’re looking for but it’s looking far more likely that objects from within the asteroid belt are responsible for the oceans we have today. What the mechanism was for them making their way to Earth, whether it was early on in the cataclysmic forming of our solar system or later on when things calmed down, is something that’s still an open question. It’s one we might also have answers to very soon as Dawn is scheduled to arrive at Ceres early next year, the biggest object in the asteroid belt. What Dawn finds there might be the key to unlocking the secrets of our Earth’s oceans and, potentially, the asteroid belt itself.
It may seem like scientists spend an inordinate time studying water but there’s a pretty good reason for that. Water is fundamental to all forms of life on Earth so understanding its origins and what roles it plays is crucial to understanding how life came to be and where we might find it. The vast majority of Earth’s water is contained in its oceans which were thought to have formed when comets bombarded its surface, seeding them across the world. However recent research has shown that the oceans may have formed in a different way and that Earth may have much more water contained in it than previously thought.
A recent study done by Steven Jacobsen and his team at Northwestern University has revealed that Earth has a subsurface reservoir that may contain 3 times the volume of the Earth’s surface oceans. They discovered this information by using data from a wide variety of seismometers, those instruments that measure the intensity of the pressure waves of earthquakes, and figuring out how the waves travelled through the Earth’s interior. This is nothing new, it’s how we’ve figured out the rough compositions of the different layers of the Earth’s inner layers previously, however Jacobsen postulated that water in ringwoodite would slow the waves. After testing a sample of ringwoodite to confirm this theory (shown above) his team found data to support the existence of a large layer of ringwoodite in the Earth’s mantle. Whilst this isn’t a subsurface ocean like some heavenly bodies in our solar system have it is a rather interesting discovery, one that supports an entirely different theory of how our surface oceans formed.
The initial hypothesis (at least the one I’m familiar with) is that the Earth bound itself together out of all the varying bits of debris that existed after the sun had formed itself. At this point Earth was a ball of lava, a fiendishly unfriendly environment devoid of any kind of life. Then, as the planet cooled, comets rained down on its surface, supplying the vast amounts of water we now see today. The discovery of this layer of ringwoodite on the other hand suggests that the water may have been present during the initial formation and that instead of other comets providing all the water it instead seeped up, filling all the crevices and crags of the Earth’s surface. It’s interesting because it now links Earth more directly to our other celestial neighbours, those which you’d never consider Earth-like at all.
Saturn’s Europa and Jupiter’s Ganymede for instance are both hypothesized to have vast bodies of water under their surfaces. Up until this discovery you would be forgiven for thinking that their initial formation was likely due to their immediate environment (I.E. those massive gas giants right next to them) however it’s more likely that all heavenly bodies form along a similar path. Thus oceans like ours are probably more likely than not for planets of similar size to ours. Of course there are also numerous other factors that can push things in one way or another (see Mars and Venus for examples of Earth like planets are nothing like Earth) but such similarities really can’t be ignored.
In all honesty this discovery surprised me as I had always been a subscriber to the “comet bombardment” theory of Earth’s oceans. This evidence however points towards an origin story where water formed a core part of Earth’s structure, only to worm its way to the surface long after it cooled. Come to think of it this probably also explains (at least partially) how Earth’s atmosphere likely came to existence, the gases slowly seeping out until it was blanketed in carbon dioxide, only to be turned into the atmosphere we know today by plants. I’m keen to see what other insights can be gleaned for this data as I’m sure this isn’t the only thing Jacobsen’s team discovered.
Correction: My good friend Louise correctly pointed out that our atmosphere started off being almost completely carbon dioxide and only had the composition we know today thanks to plans. She also pointed out I used the wrong “it’s” in the title which, if I didn’t know any better, would say to me that she wants to be my copy editor 😉
I spend an awful lot of time here (and elsewhere, for that matter) staring up at space that you’d be forgiven for thinking that I don’t pay as much attention to things that are going on back down on Earth. Whilst my true passions lie in the final frontier I still have a keen interest in the multitude of projects that have the same level of complexity as running about in space does and you’ll often see me getting lost in all manner of weird things like deep sea drilling rigs or military hardware. One project that’s really captured my attention of late, mostly due to the fact that I knew nothing about it until just recently, is James Cameron’s Deepsea Challenger project which has just begun its journey to the bottom of the ocean.
The purpose of Deepsea Challenger is to travel to what we believe is the deepest part of the ocean, the Mariana Trench. Now this isn’t the first manned dive to visit this part of the ocean as back in 1960 the Bathyscape Trieste was the first manned craft (and first craft overall) to land on the bottom of the world’s oceans. They didn’t spend much time on the bottom though, only staying for a mere 20 minutes after the nearly 5 hour journey to get there, and the craft kicked up quite a bit of silt which limited their view. Despite that though they did report that there was vertebrae life forms down there meaning that even at the most extreme of conditions complex life could still form.
Deepsea Challenger is straight out of a science fiction novel by comparison. It’s about half the size of the Trieste but it’s jam packed with all manner of equipment that Cameron intends to use whilst he’s down there. It’s also quite novel in its design favouring a torpedo like structure rather than the sub + pressure sphere that the Bathyscapes had. This design will allow Deepsea Challenger to reach the bottom in a mere 2 hours, an incredible improvement over nearly all other deep sea submersibles. Cameron then intends to spend up to 9 hours filming (in high-def 3D no less) and collecting samples before making the trip back to the surface.
The reasons why this sub matters is simple: the insights it can give us to how life evolved and continues to thrive down there gives us a much clearer idea of where life could possibly evolve elsewhere. With such extreme low temperatures and high pressures you wouldn’t expect to see anything above simple life forms, but the observations from the Trieste indicate that complex life has managed to thrive down there. Extrapolating this idea further it then means that the possibility of life on other planets in our solar system, like Jupiter’s moon Europa, is much more likely than we previously would have thought.
The reveal of Deepsea Challenger coincided with Sir Richard Branson’s announcement of yet another arm of his Virgin line of companies. This time it’s Virgin Oceanic and they’re looking to offer trips to the Mariana Trench (and other deep sea locations) to willing punters. This year will see their craft, called DeepFlight Challenger, visit 5 different locations around the world to both test the craft and generate some PR. Compared to the Deepsea Challenger its quite different, opting for a kind of submersible plane configuration that uses wings to “fly” through the water. This means that unlike the Trieste or Deepsea Challenger DeepFlight will be able to cover some serious ground while its down there. It will be very interesting to see how that craft goes in comparison to its predecessors, especially considering it’s future as a commercial venture.
Considering that we’ve only explored a mere 3% of the ocean depths the progress being made here will open up a whole new frontier for scientific research, as well as a little tourism on the side. I can’t wait to see what these two vessels discover on their journey down there and I’m sure that the discoveries will keep coming for a long time to come after their initial journeys down there. It’s hard to believe that we still have so much of our world undiscovered when we’re so connected these days but it shows that there are still many challenges to be had, and those willing to take them on.
After my last foray into the controversial world of the environment and power generation (which generated some stimulating discussion and research for me) I thought it best to take a look at the renewable means of power generation and which of them have a future. I’ve had a bit of experience with most of the technology in the past with a few of my off site engineering lectures, a requirement for any engineering degree, being held on renewable energy technologies. My father also teaches renewable energy classes at the local TAFE here in Canberra, and I’ve seen quite a few interesting projects he’s been involved with over the years.
When we talk about renewable energy sources we’re looking for something that doesn’t rely on fossil fuels. The main candidates for renewable energy are:
Now not one of these solutions can provide meet all of the energy needs of the entire world and there’s many different factors to consider. The ideal solution will probably end up with a combination of many of these technologies (and some of the ones that are currently under development) just like the power generation we use today.
First the main consideration is base load power generation. Whilst this is usually trotted out as the argument to destroy the idea of using any form of renewable energy it does have raise a key points that need to be addressed. Many of the renewable energies I’ve mentioned (in fact just over half of them) can’t produce stable amounts of power. Solar, wind and oceanic technologies vary their power output significantly depending on their environment. To solve this issue base load generating stations like geothermal and biomass have to be used to supply that base level of power. The other alternative is to invest some storage technologies, like molten salt for solar thermal. For Australia I believe that geothermal and solar thermal are probably the way to go. This is because we have so much uninhabitable land that is very dry and sunny, something that these technologies thrive on. Photovoltaics are nice for smaller installations however they currently do not scale as well as the others, although that might all change when sliver cells take off¹.
Secondly load following plants are also required in order to accommodate variations in power requirements. Biomass and Hydroelectric are both options for this however I’m not entirely sure how well they can scale up. It may be more efficient to have more base load plants and just disconnect them from the grid. Whilst that may sound counter-intuitive it would be perfectly acceptable since the energy is usually not being harnessed anyway.
The last problem I’ve seen with the implementation of renewables is the lack of ideal locations for certain technologies. Geothermal requires geysers to be present or implementation of a hot rocks plant. Wind requires either high altitude or favourable wind environments such as offshore. Solar and solar thermal require a decent amount of sun and a nice flat area. You can see where I’m going with this, there’s a fair amount of work to be done to get these things in and working.
Having said all this, I’m still all for these technologies. All of the problems I’ve put forward are nothing short of solvable and eventually we’ll be forced into implementing these solutions. The great news is a lot of the supposedly big bag oil companies are in fact on board and supporting this kind of technology. The ones who aren’t will eventually fall by the wayside and we can only hope they come around before they pull an Enron and dissolve the company.
I still believe nuclear would be a great transition technology, but only time will tell.
¹I actually had the pleasure of meeting the developer of sliver technology, Andrew Blakers, back when I was a fledgling engineer. His technology does have the potential to change photovoltaics in a way that would make them highly viable. Origin Energy has some great pictures of the cells in development, and hopefully they’ll be commercially available soon.