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Thread: Journey to the Centre of the Earth

  1. #1 Journey to the Centre of the Earth 
    Forum Freshman quasistatic's Avatar
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    This is one major issue I keep thinking about -

    We are focusing all our energy into exploring and extending the limits of the universe around us, visiting planets and using sophisticated instruments to look into deep space.

    At the same time we are studying the most basic form of matter - atoms and nuclei.

    But, why hasn't man actually attempted to dig up till the earth's solid core or send an unmanned machine or initiated any such exploratory missions delving into the earth's insides? Economic benefits are many for such a mission - The heaviest elements and minerals are present in the lower layers of the earth structure.

    I understand that the mantle itself restricts passage because of the molten rock, lava, heat and all these complications but surely science will have solutions?

    My question is,why isn't man seriously considering a journey to the centre of the earth? And what are the various physical constraints and difficulties that one would face when you attempt such a mission?


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    The deepest humans have been able to drill is about 7 and a half miles. That was in 1989.

    http://en.wikipedia.org/wiki/Kola_Superdeep_Borehole

    On average, continental crust is 25 miles thick, and up to 40 miles thick in some mountainous regions.

    I doubt that technology has advanced enough in the 23 years since 1989 for us to be able to drill all the way through the crust, much less all the way through the mantle to the outer core. The pressures become far too crushing even at just the base of the crust.

    Wild guess, maybe in 500 years or so, maybe more, technology will advance enough to make such an undertaking feasible.


    On a tangent, this seems like a major hurdle to climb if we want to send a probe some time in the near future to explore Europa's suspected subsurface oceans. Europa's outer ice layer could be 13 miles thick, maybe more maybe less depending on which model turns out to be correct. Given that the deepest we've ever drilled here on Earth is 7 miles, how are we supposed to drill twice that depth, remotely, on a world hundreds of millions of miles away? I think it will be do-able eventually, but not sure if it will be in my or my children's or my grandchildren's lifetimes. Would be a stunning accomplishment when it does happen.


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    My question is,why isn't man seriously considering a journey to the centre of the earth? And what are the various physical constraints and difficulties that one would face when you attempt such a mission?
    It is simply far beyond present day engineering capabilities. There is no conceivable design for a machine which could withstand the temperatures and pressures involved.

    how are we supposed to drill twice that depth, remotely, on a world hundreds of millions of miles away?
    You don't drill. You melt. The real challenge is to come up with a suitable power source for such an undertaking, considering that contamination of the sub-surface ocean is to be avoided at all costs.
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    Quote Originally Posted by Markus Hanke View Post
    You don't drill. You melt. The real challenge is to come up with a suitable power source for such an undertaking, considering that contamination of the sub-surface ocean is to be avoided at all costs.
    My first thought when you mentioned the contamination concern was that it rules out using a fissile power source.

    But then again, Curiosity runs on a plutonium power source. I assume they've implemented mechanisms to prevent nuclear contamination of Mars, haven't they?
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    But what if we start from the deepest point on earth, say the Mariana trench? And aren't any efforts being made in this direction at all? If not huge machines, maybe miniscule probes.
    On an off-hand note, is there any artificial or natural material that is capable of withstanding such temperature and pressure, that could perhaps form the outer protective layering for such a said probe?
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    They have tried but they all ran out of funding. That and they made Satan really angry for putting a hole in his ceiling.
    It is by will alone I set my mind in motion.
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    Forum Freshman quasistatic's Avatar
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    Well, God wasn't angry we ventured out of Earth into Heaven. Satan should be a bit more supportive too.
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  9. #8  
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    Quote Originally Posted by pikkiwoki View Post
    But then again, Curiosity runs on a plutonium power source. I assume they've implemented mechanisms to prevent nuclear contamination of Mars, haven't they?
    Not my area of expertise, but yes, I would imagine they have very strict protocols in place to prevent such an occurrence.

    But what if we start from the deepest point on earth, say the Mariana trench?
    It makes a minuscule difference when one considers the total distance to be drilled down to the core. Also, just getting down to the bottom of the Mariana Trench is a major undertaking with present day technology, let alone setting up a drilling operation there. It's just not feasible.

    And aren't any efforts being made in this direction at all?
    The only thing I am aware of is this :

    ^Ojovan M.I., Gibb F.G.F., Poluektov P.P., Emets E.P. 2005. Probing of the interior layers of the Earth with self-sinking capsules. Atomic Energy, 99, 556–562

    The idea being an unmanned probe made of an outer shell of tungsten, with an internal radioactive heat source, melting its way slowly through the mantle. This is purely a proof concept, currently.

    On an off-hand note, is there any artificial or natural material that is capable of withstanding such temperature and pressure, that could perhaps form the outer protective layering for such a said probe?
    The element with the highest melting point is tungsten at approx. 3700K ( carbon is another contender, but does not melt into a liquid phase except at very high pressures ). The compound with the highest melting point is tantalum hafnium carbide at roughly 4400K. Only tungsten could in theory be used for the construction of a probe, but wouldn't survive all the way to the core.
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    Forum Freshman quasistatic's Avatar
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    So basically, we either have to wait till a strong enough material is invented OR wait for the cores to cool down. Dark.
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  11. #10  
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    Quote Originally Posted by quasistatic View Post
    So basically, we either have to wait till a strong enough material is invented OR wait for the cores to cool down. Dark.
    Yes, that's pretty much it in a nutshell, and also the reason why no efforts are being made in that direction. It's simply not feasible.
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    Quote Originally Posted by quasistatic View Post
    So basically, we either have to wait till a strong enough material is invented OR wait for the cores to cool down. Dark.
    The core is not cooling down any time soon. It will take around 3 billion years for the outer core to completely solidify.
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    Quote Originally Posted by quasistatic View Post
    My question is,why isn't man seriously considering a journey to the centre of the earth? And what are the various physical constraints and difficulties that one would face when you attempt such a mission?
    The problem of drilling is one of engineering. Apparently the super deep borehole in Russia was a hole about as thin as a human hair at depth. You need to go thin to overcome the pressure. Thus you need a material strong enough not to break when it gets that thin. In short you need "unobtanitum". (Unobtainium is a fictional/joke material)

    That doesn't mean we can't study the deep Earth, we just have to find clever ways of doing it remotely. As for mining the deep Earth though, that's not something you'll see any time soon.
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    Why drill through crust when there are already natural openings? Admittedly the route down under - say Hawaii - is convoluted, but this answers the first problem doesn't it?

    A device that functions in the mantle must be exotic. This is a problem for creative thinking not brute force. Perhaps a probe composed of liquids. Can an "assembly" of molten metals maintain a structure?

    ***

    Kinda on topic, I propose disposal of US nuclear waste into open lava in the state of Hawaii. The Earth itself naturally drags heavy metals away from the crust.
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    Quote Originally Posted by quasistatic View Post
    but surely science will have solutions?
    Quasistatic - This attitude is very frustrating. It's the typical 'can't somebody else do it?' mentality. Assuming science has the answer and solution to all of life's problems is very narrow minded.

    Now in saying that, I'm not saying you're narrow minded, and I agree that it would be very beneficial to explore the interior of our planet. There is however, as far as I'm aware, no way of doing so as yet. And if there were, I would assume that it would be outrageously expensive.

    I'm not an expert in this field, but I'm sure there would be a wealth of information available in regards to the natural problems and technological shortcomings preventing us from attempting such a 'dig'.

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    you would first have to have material to eliminate heat, otherwise ur in an oven. you would also need to make sure that your vessel is sealed, manned or unmanned, or it will crush like a tin can. you would need a means of propulsion that work in rock and liquid. and you would have to do all this while making sure your testing equipment and other things also live up to this standard.
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    Watched a program on this recently. There are plans to do it. From what I remember the drills are 6 miles long, that have to be replaced every 60 hours.
    Couldn't find a link to the program online, but here's an article on the project:

    The $1 billion mission to reach the Earth's mantle - CNN.com

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    Pong--There are no "natural openings" through the crust. Volcanoes are really quite shallow reaching only 10 to 20 miles down but even then what you reach is a magma filled resivour under high pressure. There are no long winding caves as they show in the movies. Volcanoes are more like skin blemishes on the earth rather than penetrating wounds.

    The engineering problem is mostly one of refridgeration. How do you cool the business end of your probe when the rock itis cutting through is at 5000 degrees F? If you can keep the drill cool enough that might help to stabilize the walls of your bore hole but you will have to pressurize it as well. At some point the pressures involved exceed the strength of the rock that you have anchored your well head to and the well blows out.
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  19. #18  
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    Quote Originally Posted by pikkiwoki View Post
    Quote Originally Posted by Markus Hanke View Post
    You don't drill. You melt. The real challenge is to come up with a suitable power source for such an undertaking, considering that contamination of the sub-surface ocean is to be avoided at all costs.
    My first thought when you mentioned the contamination concern was that it rules out using a fissile power source.

    But then again, Curiosity runs on a plutonium power source. I assume they've implemented mechanisms to prevent nuclear contamination of Mars, haven't they?
    This forever fear of people and everything involving the word Nuclear. Things are not so bad. Take New York's central station. Because of all the granite it emits more radiation then would be considered allowed in a nuclear power plant. Yet millions of people cross their daily. Imagine that that same million people crawling daily through a nuclear power plant would receive LESS contamination?

    Come on, Where do you think our radiation sources come from? The earth itself.

    Most important relevant argument to the thread. Why would we want to go there? It is about as effective as a bunch of teens putting their hands in the fire and see who holds out the longest. Unless there is resources, there is no usefull gain to be made that deep. Diamonds perhaps.
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    Also in the center of the earth, if we were to make a bubble of it, is about a 2 cm wide black hole :P
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    Quote Originally Posted by Kerling View Post
    Also in the center of the earth, if we were to make a bubble of it, is about a 2 cm wide black hole :P
    can you support this assertion?
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    Quote Originally Posted by Sealeaf View Post
    Quote Originally Posted by Kerling View Post
    Also in the center of the earth, if we were to make a bubble of it, is about a 2 cm wide black hole :P
    can you support this assertion?
    Assertion Support can be found here.
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  23. #22  
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    Quote Originally Posted by Neverfly View Post
    Quote Originally Posted by Sealeaf View Post
    Quote Originally Posted by Kerling View Post
    Also in the center of the earth, if we were to make a bubble of it, is about a 2 cm wide black hole :P
    can you support this assertion?
    Assertion Support can be found here.
    Thank you I needed that!
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    Quote Originally Posted by Kerling View Post
    Quote Originally Posted by pikkiwoki View Post
    Quote Originally Posted by Markus Hanke View Post
    You don't drill. You melt. The real challenge is to come up with a suitable power source for such an undertaking, considering that contamination of the sub-surface ocean is to be avoided at all costs.
    My first thought when you mentioned the contamination concern was that it rules out using a fissile power source.

    But then again, Curiosity runs on a plutonium power source. I assume they've implemented mechanisms to prevent nuclear contamination of Mars, haven't they?
    This forever fear of people and everything involving the word Nuclear. Things are not so bad. Take New York's central station. Because of all the granite it emits more radiation then would be considered allowed in a nuclear power plant. Yet millions of people cross their daily. Imagine that that same million people crawling daily through a nuclear power plant would receive LESS contamination?

    Come on, Where do you think our radiation sources come from? The earth itself.

    Most important relevant argument to the thread. Why would we want to go there? It is about as effective as a bunch of teens putting their hands in the fire and see who holds out the longest. Unless there is resources, there is no usefull gain to be made that deep. Diamonds perhaps.
    Your post prompted me to do some searching and I found this article:

    http://www.slate.com/articles/health...et_nukes_.html

    The article gives good info (apparently), though the conclusion at the very end is garbage.

    At any rate, Plutonium-238 is being used on the Curiosity rover. Apparently, Pu-238 is relatively safe:

    The particular kind of fuel inside Curiosity is called plutonium-238. It’s the perfect stuff for the job: It’s extremely radioactive, so it gives off plenty of heat, but the type of radioactive particles (alpha particles) released by plutonium-238 can’t even penetrate a sheet of paper. As long as you don’t touch it or swallow it, plutonium-238 is safe, and with a half-life of 87.7 years, it decays slowly enough that a fairly small supply can power a spacecraft for a decade or more.
    The problems lie in producing Pu-238:

    But plutonium-238 isn't easy to come by. It doesn't exist in nature, and only two places in the world have made serious quantities of it. Both made something else: nuclear warheads. You see, plutonium-238 is really a byproduct of the process for making another kind of plutonium, known as isotope 239. Plutonium-239 is the real terror: It takes just a couple of pounds of the stuff to make a bomb as powerful as many kilotons of TNT. Almost all modern warheads in the U.S. arsenal use plutoniuim-239 as a trigger. When it explodes, it sets off an even larger thermonuclear device capable of flattening a midsized city (say, Boulder, Colo., or Ann Arbor, Mich.). Russian warheads have even higher yields.
    More info at the link provided. Just beware the sentence at the very end of the article, which, like I said, is rubbish.

    So yeah, let's use Pu-238 to melt our way through Europa's crust!
    Last edited by pikkiwoki; December 24th, 2012 at 08:33 AM.
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  25. #24  
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    Quote Originally Posted by pikkiwoki View Post
    At any rate, Plutonium-238 is being used on the Curiosity rover.
    What is being used, to be more precise, is Plutonium-238 dioxide ( PuO2 ). 4.8kg of it, neatly arranged in 32 cubes with a volume of roughly 20cm3 each. Several other space-craft use similar power sources as well.

    So yeah, let's use Pu-238 to melt our way through Europa's crust!
    Hmm, I'm not so sure whether this would work. So far as I know ( I might be wrong here ?? ) a chunk of this stuff is at best warm to the touch, but not hot enough to actually melt through a glacier.
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    ^ I hadn't thought about that.

    Now thinking about it, it seems like it would take an incredible amount of energy to melt through how ever many miles of glacier are on Europa, would it not? I'm imagining that the probe wouldn't have enough energy to actually bore a hole through the glacier like I first imagined (like an ice fishing hole). Maybe it would instead burrow through the glacier, with the liquid above it refreezing, so that the probe is encased in a sort of moving cavity, a bubble of melted water, all the way down. Just sounds like a monumental task, well beyond our technological capabilities right now.
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  27. #26  
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    Quote Originally Posted by pikkiwoki View Post
    Maybe it would instead burrow through the glacier, with the liquid above it refreezing, so that the probe is encased in a sort of moving cavity, a bubble of melted water, all the way down.
    That is likely exactly what would happen. The issue here is - how to maintain a communication link with through several kilometers of solid ice ?
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by pikkiwoki View Post
    Maybe it would instead burrow through the glacier, with the liquid above it refreezing, so that the probe is encased in a sort of moving cavity, a bubble of melted water, all the way down.
    That is likely exactly what would happen. The issue here is - how to maintain a communication link with through several kilometers of solid ice ?
    Maybe they can use some sort of umbilical system.

    The probe lands on the surface, plants a transceiver, then starts burrowing. The probe is connected to the transceiver via an umbilical that unwinds as the probe descends. The problem is the umbilical would have to be tens of miles long...
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    Quote Originally Posted by pikkiwoki View Post
    The probe is connected to the transceiver via an umbilical that unwinds as the probe descends. The problem is the umbilical would have to be tens of miles long...
    No, the problem is - how could the umbilical unwind if the hole is freezing shut again immediately behind the probe ??
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by pikkiwoki View Post
    The probe is connected to the transceiver via an umbilical that unwinds as the probe descends. The problem is the umbilical would have to be tens of miles long...
    No, the problem is - how could the umbilical unwind if the hole is freezing shut again immediately behind the probe ??

    My thought was that the spool containing the umbilical would be on the probe, not on the transceiver. The umbilical would have to be able to withstand being embedded in ice, as the refreezing ice would make the unwound parts of the umbilical become permanently embedded in the ice. But the problem like I mentioned is the length of the umbilical. The spool would have to be gigantic lol, likely bigger than the probe itself. Unless maybe we can somehow invent/design a nano-umbilical, which has microscopic diameter but of course phenomenal strength. Um yeah, like I said, way beyond our current technological abilities. We'll have to wait a few hundred years, if not more, for technology to advance.
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    Maybe not. The lander sits on top of the ice and releases the probe which just melts its way down to the point where it starts to lose radio contact with the lander. Then it stars releasing the umbilical which trails behind it freezing into the ice and serves as a very long antenna to increase the range of its radio connection to the lander. When the probe pops out of the bottom of the ice sheet the umbilical becomes an anchor to keep it from falling the rest of the way to the bottom. If you want to probe the bottom you have to make a two stage probe.
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