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 😉
Ever since getting things into orbit became a routine task the amount of stuff we’ve left floating around us in space has increased exponentially. Typically the debris that surround us are made up of the upper stages of rockets, disused satellites that can’t/won’t de-orbit for some time and, worst of all, innumerable other bits of miscellanea that are the result of things crashing into each other. This is the beginnings of a terrible self inflicted disease called Kessler Syndrome whereby the lower orbits are so littered with junk that launching anything becomes nigh on impossible, save for some drastic changes in technology. Thus it’s in our best interests to come up with some workable solutions to this issue and the engineers at the Japanese Aerospace Exploration Agency (JAXA) have come up with a very interesting solution.
Whilst most of the debris surrounding Earth will eventually make its way back down the time frame in which it will do so varies from years to centuries. Since the orbits are unstable it’s likely that they’ll change drastically over time and this means that the chance that they will collide with another bit of debris increases quite dramatically. This is the real crux of the issue as collisions of this nature create much more debris than their individual parts alone (it is also why all the collective space faring nations were a rather pissed at China for testing their anti-satellite missile). Whilst there’s not much we can do for the numerous small bits of debris orbiting Earth there’s a lot we can do for a specific type of space junk, specifically the upper stages of rockets, and this is what JAXA’s latest development targets.
The team at JAXA’s Innovative Technology Research Center have devised what they’re calling an electrodynamic tether to help combat the space debris issue. It consists of a small space craft, one could imagine something of cubesat size, that attaches to a large piece of debris via a long electrically conductive tether. Then, by virtue of the fact that Earth has a magnetic field and the tether is conductive, Lorentz forces then act to drag the two satellites back down to Earth. It’s a rather ingenious way of getting the junk to deorbit as it doesn’t rely on carrying massive amounts of propellant, making the craft infinitely smaller and far more efficient. It might only tackle a specific subset of the debris in space but their calculations show that this should be enough to prevent a runaway Kessler syndrome situation.
Probably the coolest thing about it, at least for me, was the preferred way of attaching the tether to the target. They have explored some regular options, namely coasting up to the craft and attaching it with a robotic arm, but since their targets are going to be the usually thin walled upper stages of craft they’re instead opting for a harpoon that will penetrate the hull of the craft. So in the future we could have a swarm of harpoon carrying cubesats orbiting us, ensuring that any large bit of space junk is brought to the fiery demise it so rightly deserves.
Of course this doesn’t mean the problem is completely solved but this could be enough of a stop gap solution whilst we figure out better ways of cleaning up our lower orbits. It’s not going to be an easy problem to solve, the energies required to get everything up there in the first place ensure that, but things like this show that there are highly efficient ways of dealing with it. All that’s required is for us to find them and, hopefully, deploy them before its too late.
There’s a couple iconic photographs from space that everyone is familiar with. The most recognizable is probably this one I used a couple years ago during the 40th anniversary celebration of the Apollo missions showing Buzz Aldrin standing on the dusty surface of the moon. A few other notables are ones like Earthrise, The Pale Blue Dot and the STS-1 mission liftoff (note the white external fuel tank, one of only 2 to have it) but above them all stands the Blue Marble, an incredibly breath taking view of our earth as seen by the Apollo 17 crew on their mission to the moon.
It’s a beautiful photo and one that changed my, and certainly many others, view of the world. I don’t know why I used to think this but before seeing this picture I imagined the world being mostly cloudless, not covered in the swaths of thick cloud that you see in the picture above. It also puts your entire life in perspective, much like the Pale Blue Dot does, knowing that in the end we’re all clinging to this giant water covered rock shooting through space.
Over the years NASA has set about recreating the Blue Marble as technology progressed, mostly just as an aside to one of their many Earth sensing programs. The big difference between the original and these subsequent releases is that the newer ones are composite images, I.E. they’re not a single photograph. You can see this quite clearly in the 2005 version which shows how the Earth would look like if there was no cloud cover, something that’s simply impossible to photograph. The most recent addition to this lineage of whole Earth pictures is the Blue Marble 2012 and it’s quite spectacular:
The original picture is some 8000 x 8000 pixels large (64 megapixels) and gives you an incredible amount of detail. The resolution is high enough for you to be able to pick out topographical details with relative ease and you can even see the shadows that some of the clouds are casting on the ground below them. The original article that was linked to me had a lot of interesting comments (a lot on how the Americas appear to be somewhat distorted) but one that caught my attention was a question about one of the differences between the two pictures.
Why, they asked, is there no thin blue halo in the original picture?
The halo they were referring to is clearly visible if you view the larger version of the new Blue Marble picture and seems distinctly absent in the original. The planet hasn’t radically changed (geologically, at least) in the time between the pictures so the question is a curious one. To figure this out we have to understand the differences in how both these images came to be and in there is where our answer lies.
The original Blue Marble was taken by a single 70mm Hasselblad camera with a 80mm lens at a distance of approximately 45,000KM away from the Earth. The newer version is a composite reconstruction from several images taken by the Suomi NPP satellite which orbits at around 500KM above the Earth’s surface. Disregarding the imaging technology used and the reconstruction techniques on the modern version it becomes apparent that there’s a massive difference in the distance that these pictures were taken. Looking at the halo you’ll notice that it’s quite small in comparison to the size of the Earth so as your distance from Earth increases the smaller that halo will appear. So for the original Blue Marble the halo is pretty much invisible because the resolution of the camera is insufficient to capture it. The newer picture, being much closer and having a higher effective resolution, is able to capture it.
These kinds of images are always fascinating to me, not just for their beauty but also for the story behind what went into creating them. The number of man hours that went into creating something like this that appears so simple is staggering and demonstrates that we, as a species, are capable of great things if we put our minds to it. The Blue Marble 2012 might not become the icon that its predecessor was but its still an awe inspiring image to look at and even more interesting one to contemplate.
The USA has always been wary of China’s ambitions in space and I believe it’s mostly for all the wrong reasons. Sure I can understand that the fact that China’s space division is basically a wing of its military might be cause for concern, but the same could be said for the fact that the USA’s Department of Defense’s budget for space exploration exceeds that of NASA’s. Indeed the USA is worried enough about China’s growing power in space and other industries that there’s already been speculation that it could spark another space race. Whilst this would be amazing for a space nut like myself I really wouldn’t wish that kind of tension on the world, especially when the USA is struggling as much as it is right now.
Of course that tension is enough to spark all sorts of other speculation, like for instance the true nature of the mysterious X-37B’s mission. It’s payload bay suggested that it was capable of satellite capture, an attribute shared by it’s bigger cousin the Shuttle, but its previous orbits didn’t put it near anything and it didn’t really have enough delta-v capability to be able to intersect with anything outside a few degrees of its own orbit. However since then there’s been a couple launches and one of them is smack bang in the X-37B’s territory.
The craft in question is none other than China’s Tiangong-1.
Yesterday the BBC ran an article that speculated that the USA was using the X-37B to spy on Tiangong-1. Now initially I dismissed this as pure speculation, there are far easier ways for the USA to spy on a satellite (like using one of their numerous other satellites or ground based dish arrays) than throwing their still experimental craft up in a chase orbit. However checking the orbital information for both Tiangong-1 and the X-37B shows that they do indeed share very similar orbits, varying by only 0.3 of a degree in inclination and having pretty similar apogees and perigees. Figuring this is the future and everything should be a few Google searches away from certainty I set about finding out just how far apart these two satellites actually are to see if there was some possibility of it being used to spy on China.
To do this I used 2 different tools, the first being n2yo.com a satellite tracking website. This site allows you to input the satellites you want to track and then displays them on a Google map. Once I have that I can then use another tool, this time from findpostcode.com.au which shows me the distance between two points (which thankfully also takes into account the fact the earth isn’t flat). So firstly here’s a picture of the two orbits overlapped:
So as you can see they do indeed share very similar orbits but there does seem to be an awful lot of distance between them. Just how much distance? Well the second picture tells the full story:
Just over 14,000KM which is greater than the diameter of the earth. What this means is that if the X-37B was being used to spy on Tiangong-1 it would have to peer through the earth in order to see it, something which I’m pretty sure it isn’t capable of. Also if you look at the first picture you’ll also notice that Tiangong-1 actually passes over the USA as part of its normal orbital rotation, putting it well within the purview of all the ground observations that they have control of. I’ll note that the distance between Tiangong-1 and the X-37B won’t remain constant, but they will spend a good portion of their lives apart. Enough so that I don’t believe it would be particularly useful for reconnaissance. Additionally unless the USA knew which orbit that Tiangong-1 was going to use (possible, but we’re getting deeper into conspiracy territory here) then technically Tiangong-1 launched onto the X-37B’s orbit and not the other way around (it has not changed its orbit since the second launch, unlike it did the first time).
Honestly the idea that the USA was using the X-37B was definitely an interesting prospect but in reality there’s really no justification apart from conspiracy theory-esque hand waving. The USA has far better tools at their disposal to spy on China’s fledgling space industry than a single run experimental craft that’s only on its second flight. The orbits also put them at a fair distance apart for a good chunk of the time (as far as I can tell, at least) as well making it even less likely that the X-37B is being used for spying. Still it was an interesting idea to investigate, as is most things to do with the ever mysterious X-37B.
Ever since we first discovered a planet outside our solar system way back in 1988 the hunt has been on to find another planet like our own. That’s not a particularly easy quest however as the methods that we currently have at our disposal, namely the radial velocity method (looking for little wiggles in the parent star) and the transit method (dimming of the parent star from our point of view) are heavily skewed towards finding large planets close to their parent stars. Finding a planet like ours by these methods not only requires precision tools but also great lengths of time, on the order of 2 years or so to ensure that what we saw wasn’t a fluke. Thus a planet like our own has escaped our detection because we’re simply unable to detect it.
The start of this year saw some major progress with the data from NASA’s Kepler mission. Back in January I blogged about Kepler-10b which is the smallest exoplanet that had been discovered to date. Unfortunately for planet hopefuls (and the planet as well) Kepler-10b was found no where near the habitable zone of its parent start. In fact the planet orbits its star in just under a day, putting its orbital distance at around 1/20th of the distance between mercury and our sun. The surface temperature there is enough to melt iron, eliminating the possibility for any kind of life as we know it to arise there.
However the astronomers working on the Kepler data didn’t just stop there as there. Within the wealth of Kepler data are some 48 other earth-like candidates, planets with orbital periods that places them squarely in the habitable zone of their parent stars. One of those potential candidates was Kepler-22b, a planet who’s orbit is much closer in than earth to its parent star which is a lot dimmer than our own. This mean that it was just on the edge of the habitable zone and the last piece of the puzzle was how big it was compared to earth. That last piece of the puzzle was just revealed today and Kepler-22b’s radius is 2.4 times the size of earth.
Whilst that makes Kepler-22b sound like some kind of giant it’s still within the boundaries of what we currently believe to be hospitable to life. The real kicker for Kepler-22b will be finding out its mass as currently, whilst we suspect that it’s rocky like our planet due to its position, we have no idea what its actually comprised of. Right now it could be anything from a planet covered entirely in oceans to a giant rock ball with little to no atmosphere. We can find out the mass by using the radial velocity method and I’m sure that’s the next step that NASA is taking in attempting to figure out just what kind of planet Kepler-22b is.
This might be the first exoplanet to be confirmed as being within the habitable zone but what’s more exciting is the prospect that we have another 48 candidates just waiting for their confirmations to come through. What we can infer from this is that our solar system’s composition isn’t unique and that the formation of terrestrial planets like our own is quite common. That means the conditions that brought about life on our planet are also common in other solar systems which leads to the tantalizing prospect that there’s other life out there just waiting for us to discover it. Of course it will be a long time before we manage to get there and see it for ourselves but it’s still incredibly exciting and I can’t wait to see what other kinds of planets we dredge up from the next 48 potentials.
Our Moon has been a constant source of amazement and wonder for the human species. For as long as we’ve been able to observe it from our earthly bounds it has only ever shown us one side and wobbling ever so slightly as if to tease us as to what we couldn’t see. For the longest time we speculated about what could be on the other side of our closest celestial partner with theories ranging from the mundane to the outright fantastical. Of course since 1959 when Luna 3 first photographed the far side of the moon most of that mystery and wonder has since evaporated, but even today it still manages to throw a couple curve balls our way.
One of the most puzzling aspects is the distinct difference in terrain between the near and far sides of the moon. Comparatively the near side of the moon is quite smooth with many “maria” or land seas covering its surface. The far side on the other hand is deeply cratered with a considerably more rough appearance than the side we’re all familiar with. There are many explanations for this with the most accepted being that the near side contained a higher concentration of radioactive elements when it was first formed, and this has been confirmed from data from orbiting craft. There is however a new theory that’s come out and it depicts a story of an Earth that once had two moons:
The moon is thought to have formed when a Mars-sized body slammed into the infant Earth. This threw a cloud of vaporised and molten rock into orbit, which coalesced into the moon.
Simulations have previously shown that additional moons could have formed from the debris cloud, sharing an orbit with the one large moon that survives today. Eventually, gravitational tugs from the sun would destabilise the moonlets, making them crash into the bigger one.
Building off the most accepted theory of the Moon’s formation (the Giant Impact) this new theory about the far side of the moon’s appearance postulates that the impact also created another, smaller Earth bound satellite. Now usually smaller bodies are quickly engulfed by their bigger neighbours but this smaller moon stabilized into an orbit long enough for it to fully form. However millions of years later it impacted with the current moon at a relatively slow pace of about 8,000KM/H (for reference, the International Space Station orbits at around 25,000KM/H). So instead of smashing each other to bits they instead squished together forming a turbulent far side of the moon. Such a hypothesis also explains some discrepancies between mineral concentrations on either side of the moon as such an impact would have pushed the moon’s magma to the other side.
Now whilst this theory would explain some of the phenomena we’re seeing with our celestial sister there’s not a whole bunch of direct evidence to support it. The heavily crated far side of the moon could easily be explained by the tidal locking with Earth, which means any incoming asteroids are far more likely to hit the side facing outwards. This is made all the more difficult by the fact that there has been no landed exploration of the far side of the moon and definitely no sample return missions. Getting some rock samples from the far side of the moon would provide the answers we need to rule out or pursue this theory further.
I always find it amazing how we can think we’ve explored something so thoroughly yet it can still surprise us. The moon is something we’re all so familiar with yet it’s still so foreign when you get up close and it’s origins are as mysterious and intriguing as our own. I love that these ideas could lead to us sending a sample return mission to the far side of the moon and what’s even more exciting is that such a mission would probably lead to many more questions than answers. That’s the beauty of science, it’s a never ending journey of discovery into the origins and mechanics of the universe that surrounds us.
The Internet as it stands today is the greatest revolution in the world of communications. It’s a technical marvel, enabling us to do many things that even up to a couple decades ago were firmly in the realms of science fiction. Indeed the incredible acceleration of technical innovation that we’ve experienced in recent history can be attributed to the wide reaching web that enables anyone to transmit information across the globe . So with the human race on the verge of a space revolution that could see a human presence reaching far out into our solar system a question burns away in the minds of those who’d venture forth.
How would we take the Internet with us?
As it stands currently the Internet is extremely unsuitable for inter-planetary communications, at least with our current level of technology. Primarily this is because the Internet is based off the back of the TCP/IP protocols which abstract away a lot of the messy parts of sending data across the globe. Unfortunately however due to the way these protocols are designed the transmission of data is somewhat unreliable as neither of the TCP/IP protocols make guarantees about when or how data will arrive at its destination. Here on Earth that’s not much of a problem since if there are any issues we can just simply request the data be sent again which can be done in fractions of a second. In space however the trade-offs that are made by the foundations of the Internet could cause immense problems, even at short distances like say from here to Mars.
Transmissions from Mars take approximately 3 minutes and 20 seconds to reach Earth since they travel at the speed of light. Such a delay is quite workable for scientific craft but for large data transfers it represents some very unique problems. For starters requesting that data be resent means that whatever system was relying on that data must wait a total of almost 7 minutes to continue what it was doing. This means unreliable protocols like the TCP/IP stack simply can not be used over distances like these when re-transmission of data is so costly and thus the Internet as it exists now can’t really reach any further than it already does. There is the possibility for something more radical, however.
For most space missions now the communication method of choice is usually a combination of proprietary protocols coupled with directed microwave communication. For most missions this works quite well, especially when you consider examples like Voyager which are 16 light hours from earth, however these systems don’t generalize very well since they’re usually designed with a specific mission in mind. Whilst an intrasolar internet would have to rely microwaves for its primary transmission method I believe that a network of satellites set up as anAldrin Cycler between the planets of our solar system could provide the needed infrastructure to make such a communications network possible.
In essence such satellites would be akin to the routers that power the Internet currently, with the main differences being that each satellite would verify the data in its entirety before forwarding it onto the next hop. Their primary function would also change depending on which part of the cycle they were in, with satellites close to a planet functioning as a downlink with the others functioning as relays. You could increase reliability by adding more satellites and they could easily be upgraded in orbit as part of missions that were heading to their destination planet, especially if they also housed a small space station. Such a network would also only have to operate between a planet and its two closest neighbors making it easy to expand to the outer reaches of the solar system.
The base stations on other planets and heavenly bodies would have to have massive caches that held a sizable portion of the Earth Internet to make it more usable. Whilst you couldn’t have real time updates like we’re used to here you could still get most of the utility of the Internet with nightly data uploads of the most updated content. You could even do bulk data uploads and downloads to the satellites when they were close to the other planets using higher bandwidth, shorter range communications that were then trickle fed over the link as the satellite made its way back to the other part of its cycle. This would be akin to bundling a whole bunch of tapes in a station wagon and sending it down the highway which could provide extremely high bandwidth, albeit at a huge latency.
Such a network would not do away with the transmission delay problems but it would provide a reliable, Internet like link between Earth and other planets. I’m not the first to toy with this kind of idea either, NASA tested their Disruption Tolerant Networking back in 2008 which was a protocol that was designed with the troubles of space in mind. Their focus was primarily on augmenting future, potentially data intensive missions but it could be easily be extended to cover more generalized forms of communication. The simple fact that agencies like NASA are already well on their way to testing this idea means we’re already on our way to extending the Internet beyond its earthly confines, and it’s only a matter of time before it becomes a reality.