Author Topic: Intact lava tube found on Moon  (Read 6097 times)

Online TrevorMonty

Re: Intact lava tube found on Moon
« Reply #20 on: 10/23/2017 09:15 AM »
A MX1 lander and small rover eg 5kg could be used for initial survey. Have tethered rover lowered into skylight entrance and stay suspended while it scans cave. A mission of this scale could be achieved for under $50M. MX1 and LauncherOne would be less than $20M. NB RL Electron maybe to small for this mission.

The results should be enough to plan future more capable missions.
« Last Edit: 10/23/2017 09:16 AM by TrevorMonty »

Online TrevorMonty

Re: Intact lava tube found on Moon
« Reply #21 on: 10/23/2017 09:50 AM »
It could be possible to seal section of cave creating huge internal pressurized area. This would be massive under taking as walls and floors would need coating with sealant. Engineering for sealing bulkheads would be huge and require lots of materials. As some one point out a large volume would require lot of N, which is in short supply on moon.

Here are some figures to play with, 4000m3 of Nitrogen weighs 5t. 1m long x 100m dia (half circle) cave is 4000m3. 4t at 80% with O other 20%. Operating at lower pressure w eg 10psi (10,000ft altitude) would be   2.6t. 100m length would require 260t.
A lot to deliver to moon with current transport but not that big a deal if technology and infrastructure is in place to seal this length of cave.


Offline anonymous

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Re: Intact lava tube found on Moon
« Reply #22 on: 10/23/2017 03:19 PM »
Instead of a big huge lava tube, perhaps what's needed in the early period is a reasonable-sized cave. What would be the ideal volume for an early underground lunar station? Probably no more than several thousand cubic meters at most?

Besides the lava tubes, are there any other processes on the Moon that could have created caves - perhaps smaller ones?

Here's a good article by Paul Spudis:

https://www.airspacemag.com/daily-planet/cave-living-moon-180961494/

Quote
But lava tubes are found only in the maria, which are mostly concentrated near the equator and at low latitudes. One of the biggest drawbacks to cave living on the Moon is that we don’t have any near the poles. At the poles there is near-constant sunlight, along with deposits of water ice—valuable resources essential for human habitation. Yet enjoying the advantages of underground living doesn’t require caves. It is possible to place a habitat at the bottom of a deep crater, lay out an airlock, access tunnels, electrical cables and cooling lines, and then backfill (cover over) the crater with lunar regolith (soil) using a bulldozer. This simple construction technique provides all the thermal and protection advantages of cave dwelling, without restricting the outpost location to a less than optimum locality.

The advantages of cave life seem so attractive that every time a new lunar lava tube discovery is made, there is a call to use them to live on the Moon or other planets (most recently shown in the current “Mars” television mini-series). But people live where they can make their livelihoods and on the Moon, that “pay dirt” is at the poles, in the form of water and electrical power. The Willie Sutton principle still prevails.

I entirely see Spudis' argument for why the poles are better, and I rather agree with it, but I'm not seeing why roofing over the bottom of a crater would be better than putting domes on the surface near the poles and covering them with 6 m of regolith. The problem I see with the crater approach is the difficulty of expanding the base later. Putting another layer on top would crush the lower level unless you built it with a lot of margin. And what when you want to expand again? You could bore out instead, but that gets you into issues about how you could safely do that while the base is occupied. If you have domes connected with tubes and all covered with regolith, you just put up another dome, connect it to a tube and cover with regolith.

Offline oldAtlas_Eguy

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Re: Intact lava tube found on Moon
« Reply #23 on: 10/23/2017 05:52 PM »
There are several exciting items about lava tubes.

1) they may contain frozen volatile like water
2) less time to clear and setup for use. It takes a significant amount of time to bore a tunnel. The Lava tube comes complete with a probably pre-sealed and structurally significant material already on the walls of the tube. No mining or processing needed just heat and reform into a solid glass surface.
3) possible cache of high concentrations of other low % existing in total minerals on the Moon such as Carbon.

Problem is until something goes in and takes a look and samples, the answers about what could be there is only speculation.

As Spudis says initially Poles are easier to set up an initial Base. Later with significant high speed electrically powered ground transportation (such as a HyperLoop), having large cities anywhere on the surface no longer becomes tied to where there is constant sunlight and abundance of water. Cheap transport of bulk material (including water) around on the surface with L1 and L2 based SPS 24/7 power the initial limitations favoring the Poles disappear.
« Last Edit: 10/23/2017 05:53 PM by oldAtlas_Eguy »

Offline Phil Stooke

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Re: Intact lava tube found on Moon
« Reply #24 on: 10/23/2017 06:02 PM »
"If you have domes connected with tubes and all covered with regolith, you just put up another dome, connect it to a tube and cover with regolith."

Build domes outside the crater and connect with tubes to the crater base.  There would be very little difference.  Small craters are the target here so the depth change is not much of an issue.  There may be some advantage to using a crater initially, increasing the thermal insulation and maybe radiation protection compared with a free-standing dome. 

Online TrevorMonty

Re: Intact lava tube found on Moon
« Reply #25 on: 10/23/2017 06:44 PM »
There are several exciting items about lava tubes.

1) they may contain frozen volatile like water
2) less time to clear and setup for use. It takes a significant amount of time to bore a tunnel. The Lava tube comes complete with a probably pre-sealed and structurally significant material already on the walls of the tube. No mining or processing needed just heat and reform into a solid glass surface.
3) possible cache of high concentrations of other low % existing in total minerals on the Moon such as Carbon.

Problem is until something goes in and takes a look and samples, the answers about what could be there is only speculation.

As Spudis says initially Poles are easier to set up an initial Base. Later with significant high speed electrically powered ground transportation (such as a HyperLoop), having large cities anywhere on the surface no longer becomes tied to where there is constant sunlight and abundance of water. Cheap transport of bulk material (including water) around on the surface with L1 and L2 based SPS 24/7 power the initial limitations favoring the Poles disappear.
By time we are ready for large lunar colonies, running 2500km buried water pipe from poles to lava cave shouldn't be a big under taking. Pipe doesn't need to be huge only need a few 1000 cubic meters of water a year for launch and top recycled life support water. Power would be beamed from Space Solar Satellites, building these for earth may well be colonies main business.



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Offline TakeOff

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Re: Intact lava tube found on Moon
« Reply #26 on: 10/29/2017 04:13 PM »
It might be tricky to figure out if a lava tube is safe. Lunar geology is different with other materials, lower gravity, no air or liquids, day/night temperature shifts, tidal forces, radiation, impacts, no magnetic field. A lava tube doesn't seem like a good place to start on the Moon, I think it requires much more experience from Lunar geology and construction projects.
I believe the lava tubes, like at Marius Hills, definitely should be investigated.

How could a probe explore a skylight like one of these?
Google found this:
https://www.nasa.gov/pdf/637136main_Whittaker_Presentation.pdf

The rappel example is how I imagined it.

Random thought: I wonder if the ice at the poles could also create caves or at least overhangs. I think the lunar poles have moved over time so you could imagine a situation of different layers with different amounts of ice. Or perhaps an impact within or at the edge of a crater laying magma over icy ground that disappears out from under the much stronger roof.
I think they've concluded that the Moon was tidally locked to Earth as it is today, very early on. It was its early closeness to Earth that formed the mare on its Earth facing side, because of the heat from the early Earth. So the Lunar poles seem to always have been where they are.

Offline Phil Stooke

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Re: Intact lava tube found on Moon
« Reply #27 on: 10/29/2017 04:31 PM »
A few points to take issue with here.  Heat from Earth has nothing to do with the mare basalts - the retreat from Earth after formation would have been a lot faster than the current rate, so it was already at a sizeable distance from Earth before the period of Mare volcanism.  That scenario would also produce more symmetrical maria on the nearside and none on the limbs or farside.  More to the point it doesn't allow volcanism to continue until about a billion years ago as now believed (CE5 samples will be used to try to confirm this).  But also - crucially - mare basalts are not melted surface rocks (we can see that in impact crater melt flows), they have differentiated at depth. 

The Moon was tidally locked a long time ago, but the Lunar Prospector hydrogen data show unexpected concentrations about 5 degrees off each pole, suggesting a 5 degree reorientation in the past.

http://www.nature.com/nature/journal/v531/n7595/abs/nature17166.html




Offline redliox

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Re: Intact lava tube found on Moon
« Reply #28 on: 01/11/2018 11:57 PM »
A new site may have been found near the North Lunar Pole at Philolaus Crater.  It also has the advantage of being on the Near Side.
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Online TrevorMonty

Re: Intact lava tube found on Moon
« Reply #29 on: 01/12/2018 05:54 PM »
A new site may have been found near the North Lunar Pole at Philolaus Crater.  It also has the advantage of being on the Near Side.
Here is article, watch 2nd video it is podcast by Pascal.

http://spaceref.com/moon/possible-lava-tube-skylights-discovered-near-the-north-pole-of-the-moon.html

Offline Phil Stooke

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Re: Intact lava tube found on Moon
« Reply #30 on: 01/14/2018 05:37 PM »
This is an interesting story but there are a few things to add to it.  I watched Pascal's talk (and had read the abstract as soon as it was online), and I know him personally, to make that clear.

LRO images have revealed many 'skylights' or vertical-sided pits apparently produced by collapse into a void.  Some of them are over lava tubes in areas of basalt flows, the maria, but most are not.  The others are mainly in impact melt patches around young craters, with a small number in highlands. 

I am happy to accept the interpretation that these may be skylight openings into voids, but I am not keen on the interpretation that the void is a lava tube.  This is the floor of an impact crater, where impact melt would be expected, and there is no sign of basalt flows which might include lava tubes.  The network of fractures in the crater floor is similar to many found in other melt areas.  I would be happier if this story only talked about voids and fractures but did not mention lava tubes.  In fact I got the impression from Pascal's talk that he had probably had some criticism about the mention of lava tubes, and was trying to backpedal a bit on it. 

Does it matter?  Geologically yes, in terms of composition and formation mechanism, but also practically.  Voids under fractures could be any size including rather small - both width and length.  Lava tubes would probably be longer and more coherent voids.  Fractures might have less stable walls, lava tubes probably more solid walls that would be better for building in.   In short, these might be real features but I'm not convinced they are as useful as some of the better established lava tube skylights in the maria. 

Offline Lampyridae

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Re: Intact lava tube found on Moon
« Reply #31 on: 01/18/2018 09:51 AM »
I am happy to accept the interpretation that these may be skylight openings into voids, but I am not keen on the interpretation that the void is a lava tube.  This is the floor of an impact crater, where impact melt would be expected, and there is no sign of basalt flows which might include lava tubes.  The network of fractures in the crater floor is similar to many found in other melt areas.  I would be happier if this story only talked about voids and fractures but did not mention lava tubes.  In fact I got the impression from Pascal's talk that he had probably had some criticism about the mention of lava tubes, and was trying to backpedal a bit on it. 

We don't really have an understanding of how lunar lava behaves in lunar conditions. We do know that there are big lava tubes, big enough for the forseeable future.

The entire Sea of Tranquility is a gravity-low anomaly which appears to be the result of successive lava sheet flows. Indeed, the Tranquility pit seems to be a void into a really huge lava tube with little sign of an actual tube there due to successive flows. So, we could be looking at bubbles like an Aero chocolate, buried under lots more lava and regolith - if interconnectivity is low. Not sure what the maximum size of such a bubble would be, but on the order of a kilometre is a safe bet based on structural studies of lava tubes.

There are other possibilities for voids as well. Fractured floor craters as you mention also create huge displacements, fractures which fill with lava and maybe harden on top and then drain, creating a Moria-like chasm (for all we know).

Lava tubes however are the easiest to search for and extrapolate. We know there are radar and gravity anomalies over these areas so we can get some idea of extent, coupled with surface topography. Random voids are much harder to locate and delineate. Is it really a void or is it just a crater into a low density anomaly?
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Offline Bob Shaw

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Re: Intact lava tube found on Moon
« Reply #32 on: 01/18/2018 10:21 AM »
There are several exciting items about lava tubes.

1) they may contain frozen volatile like water
2) less time to clear and setup for use. It takes a significant amount of time to bore a tunnel. The Lava tube comes complete with a probably pre-sealed and structurally significant material already on the walls of the tube. No mining or processing needed just heat and reform into a solid glass surface.
3) possible cache of high concentrations of other low % existing in total minerals on the Moon such as Carbon.

Problem is until something goes in and takes a look and samples, the answers about what could be there is only speculation.

As Spudis says initially Poles are easier to set up an initial Base. Later with significant high speed electrically powered ground transportation (such as a HyperLoop), having large cities anywhere on the surface no longer becomes tied to where there is constant sunlight and abundance of water. Cheap transport of bulk material (including water) around on the surface with L1 and L2 based SPS 24/7 power the initial limitations favoring the Poles disappear.
By time we are ready for large lunar colonies, running 2500km buried water pipe from poles to lava cave shouldn't be a big under taking. Pipe doesn't need to be huge only need a few 1000 cubic meters of water a year for launch and top recycled life support water. Power would be beamed from Space Solar Satellites, building these for earth may well be colonies main business.



Just deliver the ice in shrink wrapped packages to a 'catcher' crater 50km short of your big settlement and harvest it there. Use a captive mag-lev sled to send the ice on a suborbital lob, and do it at night as soon as the target location gets really cold). No need for intervening and highly costly infrastructure at all.

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