Slashdot Mirror
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.
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.
"The Moon Is a Harsh Mistress." Robert Heinlein, 1966.
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.
Very few volcanic pipes are diamond laden on Earth - primarily just kimberlites, which require a special type of volcano feed by very deep magma that's high in volatiles. They're almost all very old. The moon tends to be poor in volatiles and the depth requirements would be far greater to achieve the necessary pressures, at least 1/2 to 2/3rds of the way to the core.
Still, who bloody knows?
There's all sorts of gem possibilities on the moon, way too many to list here. They're probably the most valuable export-to-earth lunar resource we could mine at this point in time, as you can imagine what sort of premium the market would put on them even if they're pretty much the same as earth gems (let alone if they're mineral species not found on earth)
"TAMS shouldn't be destroyed. They should just tag us before releasing us into the wild." -- Maeglin
Same author -- The Menace from Earth (1957).
Not sure if it were "lava tubes" (it's probably been over 30 years since I read that), but the idea of giant caverns being possible due to low gravity + high atm pressure was sure there.
Wow. This internets thing is cool.
From Menace:
"Most of the stuff written about Bats' Cave gives a wrong impression. It's the air storage tank for the city, just like all the colonies have - the place where the scavenger pumps, deep down, deliver the air until it's needed. We just happen to be lucky enough to have one big enough to fly in. But it never was built, or anything like that; it's just a big volcanic bubble, two miles across, and if it had broken through, way back when, it would have been a crater."
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.
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 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.
Not that they could be sealed and made habitable.
Sealing them is pretty straightforward actually, you just use a sprayable plastic to coat to the interior. Combine that with a series of air pressure sensors throughout and a small maintenance crew and you're all set. Settling the moon isn't really a problem from an engineering perspective, the issue is economics. It's expensive to get there, it's expensive to live there and so far there isn't much we want there. The only real things that would make any sense at the moment are A) A military installation with a mass driver so that we could bombard terrestrial targets with kinetic impactors instead of nukes or B) He3 mining, which won't be useful until we develop Fusion (and only certain kinds). Given significant other space activity it might also be a useful source of raw materials available from a lower gravity well than Earth. Oh, the dark side would make an excellent astronomical observatory but that's a pretty expensive project for what you'd get out of it.
Sure, and sci fi has had anti-gravity for many decades, but I'm pretty sure that information suggesting it was actually possible would still be news.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.