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Giant Lava Tubes Possible On the Moon
schwit1 writes: New analysis of lunar geology combined with gravity data from GRAIL suggests the Moon could harbor lava tubes several miles wide. "David Blair, a graduate student in Purdue's Department of Earth, Atmospheric and Planetary Sciences, led the study that examined whether empty lava tubes more than 1 kilometer wide could remain structurally stable on the moon. 'We found that if lunar lava tubes existed with a strong arched shape like those on Earth, they would be stable at sizes up to 5,000 meters, or several miles wide, on the moon,' Blair said. 'This wouldn't be possible on Earth, but gravity is much lower on the moon and lunar rock doesn't have to withstand the same weathering and erosion. In theory, huge lava tubes – big enough to easily house a city – could be structurally sound on the moon.'" You can read their paper here (PDF). If this is so, then the possibility of huge colonies on the Moon increases significantly, as it will be much easier to build these colonies inside such lava tubes.
I don't think this is a new idea. If I recall correctly, it's come up in science fiction over the decades based on a variety of theories.
What he really means are giant lunar worms (ala Herbert). Just you wait, the first lunar colony will be smashed to bits by lunar death worms defending their ancestral homes from pesky, tiny intruders.
We could make a civilization within the series of tubes!
Yes it's an anecdote! Were you expecting original research in a Slashdot comment?
Don't we already know that these exist?
"TAMS shouldn't be destroyed. They should just tag us before releasing us into the wild." -- Maeglin
So the moon is made of Swiss cheese.
I didnt see ay mention of moonquakes. Considering these are a real and verified occurrence and considering the considerable amount of energy they release as has been recorded, any prediction of the structural integrity of lava tubes in the moon that doesnt take moonquakes into account is likely to be wrong.
"Stratigraphically the origin of agriculture and thermonuclear destruction will appear essentially simultaneous" -- Lee
Wonder if the lunar tubes would be diamond laden like on earth? Finance the building of lunar bases? Or just crash the "diamond economy"?
This reminds me of one of David Weber's book where the moon is really a giant spaceship with a thin layer of rock over the top to camouflage it. As I recall the original moon was dropped into the sun. Nobody noticed the switch since this happened long before humans were around.
One use would be for retirement communities — the thought occurred to me some 10 or 15 years ago, but then read about it somewhere in Heinlein's writings.
The low gravity of Moon would allow the elderly (and other infirm) to remain mobile for many years after they would've become wheelchair-bound on Earth... Considering the wealth of (relatively) many of the elderly in the Western world, they may be able to pay for such retirement even before some other industries take hold up there.
In Soviet Washington the swamp drains you.
There's unlikely to be much in terms of heavy metal deposits, apart from asteroid finds, which doesn't sound like a market big enough to justify the expensive of the trip. Helium 3 is a total red herring. And of course your labor and hardware costs will be through the roof due to the incredible expense of shipping consumables. Isotopic Enrichment of light elements in-situ seems quite unlikely as a consequence.
Still, I can envision a market. Just any old moon rock will always have an interest from collectors who have an interest in space, and mineral collectors in general. You could probably turn a good profit on an ongoing basis for regular shipments of small volumes of samples to be sold at very high prices.
Any gemstone finds on the moon would have an additional, and much broader market, they could probably command incredible market prices. Most precious gems are made of light elements like one finds on the moon, and in processes that could readily have occurred on the moon. There probably are new gem species that never naturally occur on earth in sizeable quantities as well. A funny one would be if moonstone was found on the moon. (Na,K)AlSi3O8 and formed in plutonic felsic rock, all of the ingredients appear to be there. :)
"TAMS shouldn't be destroyed. They should just tag us before releasing us into the wild." -- Maeglin
lunar gravity is your friend, also support structures.
TFA concludes that really large domes might be possible.
Not that are any.
Not that they could be sealed and made habitable.
Just that in the Moon's gravity they *theoretically* might not collapse.
There is no point in building large cities on the moon. Seriously, why? If you want to live underground, do it on Earth.
I want to be the founder of Moriah.
Why blow up the moon when there's so much stuff to blow up here on Earth?
I. for one, welcome our... no, wait... imagine a beowolf cluster of... um... in Soviet lava tubes, er, the tubes... the intertubes... no, no... these tubes are like a car, see, in that they... they... ok, then, Netcraft confirms that these tubes... well, but BSD is definitely... Aw, futz. I'm memeless, you insensitive clods!
I've fallen off your lawn, and I can't get up.
Blowing up the moon would be a highly efficient way to blow up stuff on earth. Assuming only random distribution of the resulting fragments.
I've fallen off your lawn, and I can't get up.
The Moon is like a series of Tubes - If Ted Stevens had been an astronaut.
Harrison's Postulate - "For every action there is an equal and opposite criticism"
There is no point in building large cities on the moon. Seriously, why? If you want to live underground, do it on Earth.
I see the Moon as the gateway to the rest of the Solar System. It's a ready source of raw materials outside of Earth's gravity well but has enough gravity to keep things from floating around much which makes living there easier than in zero-G. Lack of atmosphere and low gravity make launching anything to orbit or beyond pretty easy. Setting up an interconnected series of solar power collectors around the equator would take care of power needs. The Moon may even have enough gravity to ameliorate the worst effects of zero-G on human health.
I think a top priority should be setting up a starter base that can start bootstrapping the rest of the needed infrastructure.
Quite. It's a damned shame the way Buzz Aldrin and his crew died screaming on live TV, and on what was to be such a historic Moon-landing mission too.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
The entire point of using a lava tube is that it is its own support structure. The trouble is that lava tube ceilings, at least on Earth, do have a habit of shedding material. There's a lava tube in the Coconino National Forest in northern Arizona that has had its share of ceiling collapses and other cave-ins (which is actually how it was discovered in the first place) so there's a certain degree of greater risk when going in. For short visits the odds of being injured from a collapse is small, but I'm sure that living there would be quite risky.
I guess it'll come down to finding out if any lava tubes actually do exist on the Moon, and if so, does the surrounding geology mean they're truly stable. Given the moon's history of bombardment I wonder how many would have been destroyed in the intervening millenia.
Do not look into laser with remaining eye.
That's what GRAIL is, and yes, it's found signs of large lava tubes. So says the summary.
To fight terrorism of course.
That would have to be one hell of an explosion - not only would it have to shatter the moon, it would have to impart enough energy to the pieces to completely escape its gravitational well - less than that and the pieces would either re-coalesce or form a ring system in the Moon's orbit, depending on just how much less.
Even a truly massive explosion wouldn't be nearly as damaging to Earth as you might imagine - the Earth, as viewed from the moon, subtends only 1.2 milli-steradians, out of the total 4pi, so assuming a random distribution only about 0.00955% of the ejected material would be on a straight-line path to Earth, plus a little more whose path is sufficiently deflected by Earth's gravity to impact - everything else would either enter an elliptical Earth orbit or, if the explosion were large enough, escape the Earth's gravity as well and sail into interplanetary space (though of course many of their orbits around the sun would cross Earth's and eventually a collision would likely occur, so the next few millenia could be a little exciting). Though of course if it didn't escape the Earth we'd probably have to deal with some long-term bombardment as fragments collided and occasionally lost sufficient angular momentum to fall from orbit. Most though would probably eventually stabilize into a ring system.
Granted, the Moon is 7x10^22kg, so even 0.01% hitting Earth would amount to orbital bombardment by 7e18 kg, more than enough to do serious damage, even if it were so pulverized that it completely burnt up in the atmosphere. Still, you have to consider that the original explosion was enough to accelerate all 7x10^22 kg worth of fragments to at least 2.4 km/s (lunar escape velocity, or 2.88MJ/kg) so that they didn't fall back under mutual attraction, and all of that first 2.88MJ/kg of kinetic energy would be neutralized by the escape. Meanwhile, the specific orbital energy of the Moon relative to Earth's surface is only ~62MJ/k, so even if 100% of the Moon fragments hit the Earth you'd only get a 124x amplification factor, and if you factor in a more realistic .01% collision rate we're talking about only 1% of the initial explosion energy reaching Earth. And if the initial explosion imparted more than 2.88MJ/kg to the fragments, then you'd only get the 0.01% return on that excess energy.
All in all, you'd do far more damage to the Earth using the same amount of explosives here, rather than 400,000km away. And that's my dose of recreational physics for the day.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
These appear too many times in the article to take the idea seriously.
I am very small, utmostly microscopic.
Personally, I'd like to embark on one of these magma tubes in Dwarf Fortress. It can't be that much harder to ensure fun on than a haunted glacier, though I will have to remember to bring extra Oxygen at embark....
Tell me what we've found not what we might find.
I've decided to stop wasting my time responding to AC trolls/sockpuppets... so if you want a response from me... login.
Granted, Helium-3 would be a challenge to mine, and we don't actually have any use for the stuff yet - that would be a more long-term resource. But Lunar soil is roughly 40% oxygen, which would be an extremely valuable resource on its own (for breath-gas and LOX-using rockets). And assuming a ready source of hydrogen and/or carbon can be found there's great potential to synthesize water and rocket fuel there as well. If nothing else it would potentially be a hell of a lot cheaper shipping just hydrogen from Earth and combining it with lunar oxygen to create water and peroxide-based fuels.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
For starters, on Earth you have to deal with Earth governments, worry about Earth wars, and guard against Earth diseases. On the moon there would be potential for a fresh start - much the same motivation as moved most early Europeans to colonize the Americas. Granted it would take a far more rugged and visionary colonist to settle a dead rock than a lush continent, but so what? Perhaps the self-selection of visionaries and dreamers crazy enough to colonize the Moon would lend itself to forming a new kind of society. Worth a shot at least. It's not like the resources would be doing any more good on Earth - we've had the technology to turn the Earth into an Eden for everyone for a century at least, yet we insist on obsessing over the same damned selfish and short-sighted motives that have driven us since the dawn of civilization.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
I thought it was a collapsed lava tube. The lunar surface is pretty heavily pounded so hollow tubes are fairly unlikely, at least accessible ones.
http://michaelsmith.id.au
"This is no cave."
- Holy crap, I've got MOD points! Who thought that was a good idea.
I have hiked in that very tube (about a mile long). If you had to live in a lava tube, it would be both easy to reinforce with something like shotcrete, being close to and parallel with the surface, and easy to create new entrances. It would be ideal protection from radiation.
So, like I said. Blow up the moon, and it'll blow up a lot of stuff on earth.
I didn't say it would blow up the earth.
I didn't specify how big an explosion, other than "blow up the moon", quoting the GP, which is going to be in the darned large side just to begin with.
As for your gravity fall back idea, when the moon is fragmented, the chunks near the surface are furthest from the others, which are all further from each other, so total gravitational pull is much less, plus, any leading elements are probably moving with maximum velocity -- nothing was in their way to bang into -- and so doubly likely to escape the gravity of the remaining cloud of fragments -- the larger that cloud is, the less pull on the outer edges of the cloud will be, because the mass that CAUSED that pull/warp is moving away in all directions. It's not the same math as trying to get "a rock" off "the moon" by any means. While in the meantime, the earth's pull, sufficient to keep the whole thing as a whole in orbit at its current orbital velocity, has not diminished, and so any fragments that are coming towards the earth afterwards, hence being pulled harder, are quite likely to be pulled out of the original orbit into impact trajectories.
And just ONE fragment of the moon about the size of Long Island landing here, m. physics person, would pretty much put a period to everything you know in fairly short order. Or, on other words, what I said in the first place. Blow up stuff on earth
And that's my dose of anti-strawman for the day. :)
I've fallen off your lawn, and I can't get up.
Of course pieces of moon raining down on Earth would be devastating, my point is that it would be far *more* devastating if you simply unleashed the same amount of energy directly on the Earth instead.
As for the specific energy required to break up the moon - it would actually be even higher than that required to get a single rock off the surface. Everything on the surface has a certain gravitational potential energy which must be overcome to escape the gravity well, as you go deeper that energy requirement increases. The fact that you're moving other pieces away at the same time changes nothing - conservation of energy requires that that energy debt be paid in full to get the pieces to stay apart rather than falling back in on themselves, regardless of whether only a single rock is being launched, or the entire thing vaporized.
As for stuff being "pulled in to the Earth" - if it doesn't hit on the first pass, it's, for the most part, not going to hit. Neglecting the complicating factors of the rapidly dissipating gravitational well of the ex-moon, every frgment will, at the moment of ejection, be on an elliptical orbit around the center of the Earth. Some of those ellipses will intersect the Earth, in which case that fragment will collide on it's first pass, everything else will continue to orbit in that ellipse forever* - there's no resistance in space to slow things down so that the Earth can catch things on the next pass. And since the Earth is the primary, there's no "gravitational keyhole" games that can be played to fine-tune the orbit for future collisions, as can happen with asteroids orbitting the sun.
* of course that dissipating gravitational well *will* confound things - instead of one big well you have many small ones all in different, but intersecting orbits (every orbit will initially pass through the space previously occupied by the moon - conservation of momentum dictates that the center of mass of all the fragments remain unchanged after the explosion - just like a rocket ship: the center of mass of fuel+ship never moves). As those fragments gravitationally interact with each other they will tend to circularize and coalesce into a ring system, but in the process some fragments will lose too much angular momentum and fall to Earth, while others will get thrown out at velocities that will escape from the Earth altogether. But mostly anything that approaches the Earth will be on a near-miss trajectory, and will rapidly be deflected onto a safer trajectory after a few more orbits interacting with it's peers - just as comets and asteroids rarely hit the sun: as objects get closer their tangential velocity increases dramatically, making them far less responsive to the gravitational pull. The only way they can hit the Earth is if their orbit gets stretched into such a long, narrow ellipse that it intersects the Earth itself.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
This in the same week that The Clangers make a reappearance on English TV....
We must not allow a lunar lava-tube gap!
That one probably is easy to fix as it's small. The ones on the Moon that people are talking about are supposed to be stadium-sized though, which means reinforcing a void that large is significantly more complicated. We could truck rebar up to the mouth of the cave in Arizona and run hoses to pump in concrete there, but on the Moon there is no cement factory and attempting to send that much rebar up would be cost prohibitive, and that's before even looking at the actual construction labor aspect of reinforcing it.
Do not look into laser with remaining eye.
You wouldn't use Earthly gunite on the Moon, but something more like epoxied regolith over carbon fiber mesh. The principle is the same. The article cites the possibility of large lava tubes. If those exist, there will be smaller tubes that will be early candidates for reinforcement.
Applying the same explosive force required to blow up the Moon to blowing up a portion of the Earth instead would only be "more devastating" if you are purely measuring devastation potential in terms of forces of impact or explosive forces.
Don't forget that by and large, the opinion of the Moon in its relationship with life on Earth is more or less "vital". We have no idea what would happen to our weather and atmosphere, our oceans and water tables, or our life cycles if the Moon were obliterated.
"Stratigraphically the origin of agriculture and thermonuclear destruction will appear essentially simultaneous" -- Lee
You are grossly underestimating the energies involved. Oh goody, Google located someone else who's already done the math (https://answers.yahoo.com/question/index?qid=20090102113458AADvZ2j)
Their conclusion was that to destroy the moon (i.e. completely neutralize the gravitational potential energy lost to the accretion of mass) would require 1.2445 x 10^(29) Joules, or the equivalent of 592.6 billion Tsar Bomba fusion bombs (the largest nuclear bomb ever detonated, at ~54 megatons of TNT, with a total destruction radius of 35 kilometers = 3848 square km). Now the surface of the Earth (land and sea combined) is only 510 million square kilometers, so we're talking the energy equivalent of 1,162 Tsar Bombas being detonated on every square kilometer of the planet. Or for an even more personal feel - if you live in a moderate-density urban area with 1/5 acre lots, that's one bomb capable of totally destroying Paris and the entire surrounding urban area (or New York City, three times over), dropped on *every* *single* *house*.
Somehow I think life on Earth would have a much easier time adapting to a little orbital bombardment and not having a moon anymore.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Well then. Unless your figures are wrong (who knows?) then I guess I stand corrected.
"Stratigraphically the origin of agriculture and thermonuclear destruction will appear essentially simultaneous" -- Lee