Author Topic: Impact of lunar free water on Exploration Architecture  (Read 28414 times)

Offline Warren Platts

The theory of a bone-dry Moon was a reasonable hypothesis after the Apollo missions. Arguably, it initially led to a confirmation bias that discounted early evidence of a wetter Moon--such as the discounting as contamination of trace amounts of phyllosilicates in certain Apollo samples (that should be reexamined IMHO).

The Giant Impact theory was proposed post-Apollo (Hartmann & Davis 1975) to explain the apparent depletion in volatiles (and siderophiles). The idea was that the Theia impactor plus a big chunk of the Earth's mantle vaporized, and as the cloud condensed to form the Moon, most of the volatiles were lost to space. Thus, one might expect that the volatiles that remained, would be enriched in heavy isotopes. Lunar hydrogen isotopes do show a slight enrichment in deuterium, but it is very slight, and they are much less enriched than comets. (Saal et al. 2013).

Given a common origin, composition, and concentration of H2O on both the Earth and the Moon, it could be that it would be a lot easier to obtain water sufficient to support an aggressive space exploration program by simply drilling for it a select Near Side, low latitude locations than it would be to mine water ice from the lunar poles. To draw an analogy with Earth's petroleum industry, getting water from the lunar poles would be as if our first petroleum had to be extracted from Alberta tar sands, rather than shallow Pennsylvania oil wells.
« Last Edit: 05/21/2016 07:18 PM by Warren Platts »
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Offline the_other_Doug

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Re: Impact of lunar free water on Exploration Architecture
« Reply #1 on: 05/21/2016 06:24 PM »
The myth of a bone-dry Moon was a reasonable hypothesis after the Apollo missions. Arguably, it initially led to a confirmation bias that discounted early evidence of a wetter Moon--such as the discounting as contamination of trace amounts of phyllosilicates in certain Apollo samples (that should be reexamined IMHO).

The Giant Impact theory was proposed post-Apollo (Hartmann & Davis 1975) to explain the apparent depletion in volatiles (and siderophiles). The idea was that the Theia impactor plus a big chunk of the Earth's mantle vaporized, and as the cloud condensed to form the Moon, most of the volatiles were lost to space. Thus, one might expect that the volatiles that remained, would be enriched in heavy isotopes. Lunar hydrogen isotopes do show a slight enrichment in deuterium, but it is very slight, and they are much less enriched than comets. (Saal et al. 2013).

Given a common origin, composition, and concentration of H2O on both the Earth and the Moon, it could be that it would be a lot easier to obtain water sufficient to support an aggressive space exploration program by simply drilling for it a select Near Side, low latitude locations than it would be to mine water ice from the lunar poles. To draw an analogy with Earth's petroleum industry, getting water from the lunar poles would be as if our first petroleum had to be extracted from Alberta tar sands, rather than shallow Pennsylvania oil wells.

You do realize that what you characterize as the "myth" of a bone-dry Moon is still the accepted model of the Moon amongst the planetary science community?

You may have a valid point -- but to start out by declaiming that the currently accepted models and theories are myths isn't exactly the best way to begin, IMHO.  It's sort of like going to the New Physics section and reading people's posts that start out with "the myth of Relativity has been accepted for far too long, you all need to discard it and accept my turtles-all-the-way-down theory in order to understand how we can get to other stars in days."

In other words, I'm not sure this forum is the best place to attack, or even insist that we re-think, the current models and theories of lunar creation and composition.  Which would strongly argue that you will never be able to find underground ice reservoirs as you describe on the Moon.

In summary, your post isn't about lunar exploration.  It's a "what-if everything we understand about the Moon is wrong?" post.  And I'm really not sure that's an appropriate topic for us to entertain.
-Doug  (With my shield, not yet upon it)

Offline Warren Platts

You do realize that what you characterize as the "myth" of a bone-dry Moon is still the accepted model of the Moon amongst the planetary science community?

All right, I changed it to "theory". That should satisfy you. However, you are wrong that the theory that the Moon is "bone-dry" is still the accepted model amongst the planetary science community. That tells me you are not an expert in the subject, and therefore, you may want to do a little research before making such pronoucements.

Quote
In summary, your post isn't about lunar exploration.

And this is a crock as well. What's got me motivated was a recent post by Dennis Wingo on his blog that reviews Paul Spudis's latest book, The Value of the Moon, where Dennis briefly summarized the infrastructural problems that mining water out of permanently shaded craters:

In order to mine water in hundred ton lots, you need a lot of infrastructure.  You need front end loaders, dump trucks, and a plethora of other surface vehicles, whether robotic or human operated.  You need lots of electrical power to provide the energy to these vehicles ... I would posit that these plans for massive water harvesting ... are to be set aside and removed from our thought toolbox, at least for a while.

Thus, rather than going directly for the water, Mr. Wingo would seem to suggest that we should build a manufacturing base first, in order to manufacture the dump trucks, etc. required to mine water in 100 tonne lots. I'm not sure how many hundred ton lots he thinks we should mine in a year, but to be game changing, it's going to have to more than one hundred mT per year:

1 tonne/yr ---> good demonstration project
10 tonne/yr ---> can launch a lander or two back into orbit
100 tonne/yr ---> will make a dent in the cost of a moon base
1000 tonne/yr ---> enough for a self-licking ice cream cone
10,000 tonne/yr ---> enough to support an aggressive, sustainable, abundant chemical Mars architecture

Dennis has a point: to ship all the mining infrastructure necessary for game-changing amounts of lunar fuel is going to be huge. You could probably send an Apollo-on-steroids crewed mission to Mars for the amount of upmass it would take to do 10,000 tonnes per year at a 30 K crater.

Thus, it is not surprising that the original VSE program never got any traction to get off the ground.

I say now that the old regime is about to give way, it's time to radically rethink our options. A lot has been learned since 2008. The evidence for a Moon's mantle/crust that is/was as "wet" as the Earth's can be partially summarized as follows:

1. The fire fountain volcanoes that produced Apollo 15 and 17 glasses contain up to 1 ppt of H2O in melt inclusions.
2. Trace amounts of apatite--a water containing mineral--are widespread and indicate similar concentrations.
3. GRAIL results that show the Moon is "fracked" down to 80 km, thus allowing a potentially huge source rock volume to provide water that could make it's way to the surface.
4. The Kola Superdeep Borehole on Earth found water described as "boiling" with H2 gas at a depth of 12 km down: that is roughly equivalent to 72 km down on the Moon.
4. LADEE results that show surprisingly high amounts of H2 gas in the lunar exosphere that is consistent with outgassing of juvenile volatiles.
5. The documented existence of geological structures that most closely resemble terrestrial maars that were formed as the result of phreatomagmatic eruptions.

The latter in particular show the way forward IMHO. In the early days of petroleum exploration, they didn't do massive seismographic and gravimetric surveys to find oil. They simply looked for natural oil seeps and drilled there.

The other thing is that I have been invited to discuss these ideas at the 7th annual joint Space Resources Roundtable/Space and Terrestrial Mining Sciences Symposium at the Colorado School of Mines in a few weeks, so I'd like the opportunity to bounce these ideas off the NSF community. I hope that's alright with you Doug!  :)
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline the_other_Doug

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Re: Impact of lunar free water on Exploration Architecture
« Reply #3 on: 05/21/2016 08:50 PM »
I've read the same results you have, and while they indicate that there was some water in the materials that formed the Moon, they don't (at least to the reviewers I've read, anyway) indicate that there are reserves of water ice waiting to be mined.  With the kind of "big splat" dynamics that I've seen discussed in detail, while a lot of the volatiles were lost to space, a lot of interactions happened on the initial clump of matter that served as the gravitational focus that built up the mass of the current Moon.  Some water was trapped inside, and is seen in the various areas you mentioned.  This supposedly accounts for the minute traces of water found in the examples you mention.

But, heck, the appearance of some arguably chondritic materials in the inclusions you mention in the Apollo 15 and 17 fire-fountain glasses have spurred Jack Schmitt to claim that the "big splat" theory is fundamentally flawed, to the extent he doesn't believe in it.  And he's the only planetary scientist who ever actually visited another planet.

And yet, his point of view is a decided minority opinion out there.

That said, it's certainly not a bad thing to follow up on all sorts of varying theories that have some basis in the observed data.  And if there are ways to establish the truth of whether or not there is ice to be mined on the Moon (except for the comet-impact-emplaced water at the poles), yeah, go for it.  But I think you need to identify the truth of that theory, and locate the buried water, before you go about setting up the infrastructure required to mine it.  We know there is water at the poles; the location and accessibility of subsurface water ice deposits are both debatable at present.

But again, that said, there is nothing but good to come from initial planning for mining such water, should it be found.  My only concern, as I mentioned, is that your new lunar composition paradigm, while interesting to discuss, is not the majority opinion out there, at least from what I've read in the journals.  The old paradigm has to do a little fast footwork to account for the current anomalies, totally granted -- I just didn't think that discussion of the various current theories of lunar origin and composition was appropriate for this particular site.  Though, as you can tell, I'd love to get into such a good discussion -- I'm just not sure what forum would be appropriate for it.

Good luck with your presentation, by the way.  Even if it's not considered to be something appropriate for this forum in particular (which I sort of hope won't happen), I'd love to see your presentation materials at some point.  Maybe after you've given your presentation, you can post something about it here?

Again, I wasn't trying to say you're not doing good work.  Just that debates on lunar origin and composition theories might not be appropriate here... but if found to be what you're predicting, your mining thinking most certainly is!  :)
-Doug  (With my shield, not yet upon it)

Offline Warren Platts

With the kind of "big splat" dynamics that I've seen discussed in detail, while a lot of the volatiles were lost to space, a lot of interactions happened on the initial clump of matter that served as the gravitational focus that built up the mass of the current Moon.

A point of nomenclature: the Moon-forming event should be called "giant impact" IMHO; the impact of a secondary moon that allegedly caused the formation of the lunar highlands (Jutzi & Asphaug 2011) should be called "big splat". Yes, some people call the giant impact "big splat", but really that's confusing, besides not being an apt description: the more recent simulations that have tried to explain the similar Earth/Moon mantle composition (e.g., Canup 2012) are not very splat-like: the two bodies completely fuse and become well mixed, with a halo of debris that becomes the Moon. Quite unlike carapace formed by Jutzi and Asphaug's big splat.

Quote from: Doug
I've read the same results you have, and while they indicate that there was some water in the materials that formed the Moon, they don't (at least to the reviewers I've read, anyway) indicate that there are reserves of water ice waiting to be mined.

That there are reserves of water ice "waiting to be mined" is not really debatable any more. Between the bistatic radar results (Spudis et al. 2013) and the LCROSS spectroscopy results (Colaprete et al. 2010), it's pretty clear that there's a lot of water up there. Indeed, the Spudis paper cited above underestimated the amount of ice in the anomalous craters by an order of magnitude (they report 600 million tonnes of ice: it should be 6 billion tonnes). In fact, there's so much ice, it's hard to explain all of it as coming from comets and meteors and solar wind: probably juvenile water provides a significant percentage of the polar ice deposits IMO.

But the purpose of this thread is not to discuss mining water ice, it's about drilling for economically valuable volatile resources at certain, rare, low-latitude, Near Side locations.

Quote from: Doug
But, heck, the appearance of some arguably chondritic materials in the inclusions you mention in the Apollo 15 and 17 fire-fountain glasses have spurred Jack Schmitt to claim that the "big splat" theory is fundamentally flawed, to the extent he doesn't believe in it.  And he's the only planetary scientist who ever actually visited another planet. And yet, his point of view is a decided minority opinion out there.

I never said the giant impact theory of the formation of the Moon is false. The beauty--and weakness--of that theory is that it can explain practically anything, and not just for the Earth-Moon system, but for the rest of the planets as well. Venus doesn't have a moon? No problem: the giant impactor merely got ejected. Uranus is tilted sideways? No problem: a giant impactor knocked it on its side. The Moon is bone-dry? No problem: the cloud caused by the giant impact caused it to lose all its volatiles. The Moon really has the same primordial concentration of water as the Earth? No problem: you can make a numerical simulation do anything you want.

So I have no problem with the giant impact hypothesis per se--it just has to be constrained by the empirical evidence of abundant juvenile water. And certainly, at least the upper layers of the Moon have been depleted in volatiles. But I believe this was a relatively gradual process that happened after the Moon formed.

The GRAIL results say the Moon is fracked to a high porosity on the order of 12% on average down to a depth of perhaps 70-80 km (Wieczorek et al. 2013). Beyond those depths, the mantle is too hot and plastic to maintain pores over geologically long periods. However, the pressure at 75 km down with a temperature of 200 C, it's hard (for me) to imagine that those pores could remain open if there was not a fluid within them pressurized to lithostatic pressures. That is what I want to talk about. I think the Kola Superdeep Borehole has much to say in this regard...

Quote from: Doug
I just didn't think that discussion of the various current theories of lunar origin and composition was appropriate for this particular site.  Though, as you can tell, I'd love to get into such a good discussion -- I'm just not sure what forum would be appropriate for it.

I've been posting on NSF since 2008; there must be a hundred threads here that get into the nitty gritty of lunar geology. Anyways, you can't discuss lunar resource exploration without discussing how those resources get formed. And you can't discuss how lunar resources get formed unless you discuss how the Moon itself was formed. Otherwise it would be like a petroleum or mining geologist on Earth who didn't believe in plate tectonics. I have heard of such characters, but they are rare birds.

Quote from: Doug
Good luck with your presentation ... I'd love to see your presentation materials at some point.  Maybe after you've given your presentation, you can post something about it here?

I'm planning on it, assuming I can raise the funds to get there!  ;D
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline savuporo

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Re: Impact of lunar free water on Exploration Architecture
« Reply #5 on: 05/22/2016 05:11 AM »
Given a common origin, composition, and concentration of H2O on both the Earth and the Moon...

This isnt established, by far. One recent example:
http://www.nature.com/ngeo/journal/v7/n6/full/ngeo2173.html

Quote
The conventional wisdom that the Moon is virtually anhydrous has been overturned. Even with the uncertainties in interpreting the H2O contents of apatite, it is unambiguously clear that the mantle source regions for the volcanic glasses contain as much water as the terrestrial mantle sources for MORBs. However, the striking similarity in the water contents of MORBs and lunar volcanic glasses should not lead one to conclude that the Moon has Earth-like water abundances. The MORB mantle represents the driest region of the terrestrial mantle. The terrestrial oceans alone represent about 230 ppmw of the bulk Earth's water, more than double what has been estimated for the volcanic glass source regions1. In addition, the KREEP-related rock source regions seem to contain considerably less water than the mantle sources for the volcanic glasses, possibly only a few ppmw. Even if the Moon did have a bulk water content like those of the volcanic glass source regions, it would not raise questions about the validity of the giant impact model for the Moon's origin, as some have proposed.
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Offline the_other_Doug

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Re: Impact of lunar free water on Exploration Architecture
« Reply #6 on: 05/22/2016 03:38 PM »
Given a common origin, composition, and concentration of H2O on both the Earth and the Moon...

This isnt established, by far. One recent example:
http://www.nature.com/ngeo/journal/v7/n6/full/ngeo2173.html

Quote
The conventional wisdom that the Moon is virtually anhydrous has been overturned. Even with the uncertainties in interpreting the H2O contents of apatite, it is unambiguously clear that the mantle source regions for the volcanic glasses contain as much water as the terrestrial mantle sources for MORBs. However, the striking similarity in the water contents of MORBs and lunar volcanic glasses should not lead one to conclude that the Moon has Earth-like water abundances. The MORB mantle represents the driest region of the terrestrial mantle. The terrestrial oceans alone represent about 230 ppmw of the bulk Earth's water, more than double what has been estimated for the volcanic glass source regions1. In addition, the KREEP-related rock source regions seem to contain considerably less water than the mantle sources for the volcanic glasses, possibly only a few ppmw. Even if the Moon did have a bulk water content like those of the volcanic glass source regions, it would not raise questions about the validity of the giant impact model for the Moon's origin, as some have proposed.

Thanks!  I had become aware of new work on the fire-fountain glasses a while back; for some reason, I seem to recall reading about a variety of new work on the glasses longer ago than the Nature article states, in fact.  ISTR becoming aware of it more like 10 to 15 years ago, while the linked article seems to indicate I couldn't have heard about it until far more recently.  I particularly recall the comments that the apatite found in lunar samples has a similar hydration level to the MORBs, and that this is indicative of heterogeneous distribution of what Warren calls juvenile water in the early accretion of the Moon.

Heck, there was a lot of discussion even back in the 1970s and 1980s that a number of different volatiles, including water, were of necessity involved in the fire fountains.  That was the first point at which I became aware that volatiles had, by definition, been incorporated into the lunar lava melts -- else, what had powered the fire fountains?

So, as I say, I know I had been aware that volatiles had been detected in some of the fire fountain glasses, and I was aware of the apatite that had been found in the samples.  I was not aware that there had been any new papers that supported speculations on relatively large underground deposits of water ice located close enough to the surface, in non-polar locations, for utilization.

My understanding was that there was a certain amount of hydrated minerals from water included in the mare melts, and that all of the melts have since basically frozen out and expressed themselves in all of the lava flows and fire fountains, etc., that occurred between four and one billion years ago.  Basically, that the Moon had already vented most all of its "free" volatiles, leaving only some hydrated minerals -- not actual water ice deposits.  In other words, that in terms of accessible water resources, the polar deposits were pretty much it.  Leaving the majority of Moon "bone-dry" for practical purposes.

I'll be doing some more literature searches in the next few weeks to see if there is anything that changes the landscape since the linked Nature articles published two years ago.  But, I gotta say, I was certain I had read about all of this longer ago -- the moral of the story is that life becomes an adventure when your memory filing system starts to lose its date headers...  ???
-Doug  (With my shield, not yet upon it)

Offline Bob Shaw

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Re: Impact of lunar free water on Exploration Architecture
« Reply #7 on: 05/22/2016 03:56 PM »
I wonder if Lunar surface 'swirls' are in any way associated with volatiles? So far as I can see, there are several competing theories for their origin, none of which cover all the bases.

If swirls are dependent on a dwindling source of volatiles (as well as the other mechanisms) then they might be more readily explained - in particular, the business of some swirls being associated with magnetic anomalies and some not. Might we posit a magnetic field associated with charged H and O2 from water, interacting with the Solar Wind and the Earth's magnetotail? And, as volatiles are depleted, such a field might depart.

Just a thought, but potentially useful for some target sites...

https://en.wikipedia.org/wiki/Lunar_swirls
« Last Edit: 06/04/2016 11:01 PM by Bob Shaw »

Offline Warren Platts

Given a common origin, composition, and concentration of H2O on both the Earth and the Moon...

This isnt established, by far. One recent example:
http://www.nature.com/ngeo/journal/v7/n6/full/ngeo2173.html

Quote
The conventional wisdom that the Moon is virtually anhydrous has been overturned. Even with the uncertainties in interpreting the H2O contents of apatite, it is unambiguously clear that the mantle source regions for the volcanic glasses contain as much water as the terrestrial mantle sources for MORBs. However, the striking similarity in the water contents of MORBs and lunar volcanic glasses should not lead one to conclude that the Moon has Earth-like water abundances. The MORB mantle represents the driest region of the terrestrial mantle. The terrestrial oceans alone represent about 230 ppmw of the bulk Earth's water, more than double what has been estimated for the volcanic glass source regions1. In addition, the KREEP-related rock source regions seem to contain considerably less water than the mantle sources for the volcanic glasses, possibly only a few ppmw. Even if the Moon did have a bulk water content like those of the volcanic glass source regions, it would not raise questions about the validity of the giant impact model for the Moon's origin, as some have proposed.

This reinforces what I've been saying. I don't deny a giant impact, as it's pretty much consistent with any conceivable suite of empirical evidence. The idea that a bunch of volatiles would be lost during such an impact was always an assumption rather an empirical fact. Alternatively, volatiles could have been lost during the giant impact, but must have then been restored through more impacts right after the Moon's formation.

As for heterogeneous distributions, that's also what I'm saying: you can't just drill anywhere and expect to hit water. The lunar glasses examined so far show water concentrations on the order of MORBs, that is around 0.2% (2,000 ppm). These may be the driest oceanic basalts; basalts associated with mantle plume hot spots tend to be significantly wetter. There is no evidence I'm aware of that the lunar samples so far examined have came from hotspot locations. Lunar hotspot plumes could have water contents on the order of 1% or more. These are the areas we should be looking at for exploration purposes IMO.

Thus it is probably not a coincidence that the canonical surface feature thought to be formed by an outgassing event(s) is the Ina D-caldera that happens to be perched atop a low shield volcano at the intersection of two major rille systems. Probably the water "source rocks" underlying Ina are much wetter than even the wettest glass samples measured so far. Since the Earth and Moon mantle are so similar, we are warranted in assuming a ~1% primordial water concentration for the rock underlying the Ina D-caldera.

I agree that a giant impact probably formed the Moon (although the fission hypothesis is still alive IMO), and that the water distribution is highly heterogeneous within the lunar interior.
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Online redliox

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Re: Impact of lunar free water on Exploration Architecture
« Reply #9 on: 05/22/2016 08:43 PM »
Short answer: lunar water is only going to affect lunar architectures.  If NASA decides to go to Mars, the simplest way to get there is a straight line that bypasses Luna.  It'll be useful for lunar colonies and ascending from Luna, but not much beyond Cislunar space; it's more fuel conservative otherwise to avoid the lunar gravity well for missions beyond Earth.
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Offline Warren Platts

One big difference between the Earth and the Moon is that water in the Earth's mantle is recycled: subduction zones send water back down into the mantle that compensates for the water lost at mid-oceanic ridges and other volcanos. On the Moon, once water makes it to the surface, it is basically lost to the interior forever. (OTOH, since there is more mantle circulation on the Earth, water is lost at a faster rate, so it's somewhat a wash.)

But might there be other mechanisms that could move water into lunar crust beyond its primordial concentration? I propose a mechanism that I call impact pumping that is analogous to the action of seismic pumping on Earth (Sibson et al. 1975).

The way seismic pumping works is that at a zone undergoing a lot of shear strain (as in a transform fault), the rock will want to stretch in the direction of least  compressive forces, causing fractures to propagate in the orthogonal direction. The fractures allow the rock to stretch without requiring plastic deformation. These fractures will then fill with fluids. Then, when the earthquake finally happens, the tensional strain is released, thus overpressuring the fluid-filled pore fractures. The fluid will then cause hydrofracturing in the direction of least compressive forces--straight up in this case. The main flow will go up the main fault line if it can, allowing large amounts of fluids to be moved large distances in short times.

Impact pumping would be rather similar. The Moon's mantle is technically a solid in that shear waves can propagate through it; thus it can be fractured. The depth of the fracture zone beneath an impact is very roughly equal to the crater's diameter. Since the permanently fracked zone extends down to about 80 km according to the GRAIL results, then impact craters wider than 80 km must have caused fractures below the permanently fracked zone. The resultant pore spaces could be expected to fill with fluids composed of volatiles dissolved in the rock. But since the rock will readily deform plastically, such fractures will be short lived: as the pores exceed lithostatic pressure, the relatively weak rock will readily give way, allowing the fluid to be squeezed upward into the lower permanently fracked zone. The pores will close up and heal as soon as the fluids are squeezed out.  In this manner, local zones could be radically enhanced in water above and beyond what's contained in their primordial bulk water content.

Empirical evidence, I think, may be found in the rather similar rimless hollows of Mercury. While they share an overall morphological similarity to the lunar hollows, there are some differences. Number one being that there are like 10 times as many of them on Mercury (400+) as there are on the Moon (40+). However, the vast majority (but not all) of the Mercury hollows are found within impact craters. It could be a similar impact pumping mechanism squeezed volatiles on Mercury upward, thus excavating the rimless pits.

However, even with impact pumping, it is hard to conceive a phreatic zone on the Moon that could extend all the way to near surface depths, because the lunar crust is so fracked, with an porosity of ~12%. As an example, consider a single cubic meter of primordial lunar rock. Assuming a 10% porosity, then are 100 L of pore space within the rock. If the rock has a density of 2800 kg/m3 and 1% water by weight, then if all water is taken out of the rock, then 25 L of water will be produced, thus filling up only 25% of the pore space.

Thus, if the fracked zone extends down to 80 km, then even if zero water was lost to space, the phreatic zone would only fill up the lower 20 km of the fracked zone. Impact pumping could increase this somewhat, and locally, intruding mantle plumes could bring in more, but still most of the fracked zone will not be filled with water. Furthermore, the vacuum of space will extend down into the fracked zone that is not filled with fluid, barring impermeable layers. If the entire fracked zone were connected by a system of cracks that led all the way to the surface, the entire fracked zone would be sucked dry, probably on the order of 107 years (cf. Stern 1999). This is all consistent with the fact that Apollo didn't find signs of hydrothermal veins, as well as the "quality factor" discussed in box 1 of the Robinson & Taylor paper that Savuporo linked to above, whereby seismic waves propagate more readily through rocks whose pore spaces are filled with vacuum.

On the other hand, the tiny channels that connect pore spaces in rocks tend to get clogged by minerals, and high pressures and temperatures cause cracks to heal, and there could be local places where intrusive sills form impermeable caps that trap water in the deepest layers of the fracked zone. So there very well could be hydrothermal deposits, it's just that they form very deep in the Moon, and the Moon lacks the uplift processes on Earth that lift up entire mountain chains only to have the tops eroded away, exposing deeply formed hydrothermal deposits. The place to look for these on the Moon would be in superdeep, giant craters floors where most or all of the crust has been excavated. But that's another story.

Then there are the rimless hollows themselves. The evidence is that they formed very recently in geological terms, so some volatiles must still be trapped in deeper layers. The hard part is coming up with a model that can allow such volatiles to migrate to near surface depths in large enough quantities to be involved in such violent excavations....
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline Phil Stooke

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Re: Impact of lunar free water on Exploration Architecture
« Reply #11 on: 05/22/2016 10:08 PM »
"The conventional wisdom that the Moon is virtually anhydrous has been overturned."

I would prefer to say it has been slightly adjusted.  A little bit of water, not a lot.

"the canonical surface feature thought to be formed by an outgassing event(s) is the Ina D-caldera that happens to be perched atop a low shield volcano at the intersection of two major rille systems."

It might be on a shield volcano, but that's only one interpretation of the topography.  It's not a caldera.  It certainly is not at the intersection of two major rille systems.  Also we now have lots of Ina-like objects, some which actually are associated with volcanic domes (near Cauchy) and an ancient caldera rim (west of Tobias Mayer) - so other Ina-like features make that case better than Ina does.  Lastly, the volatiles associated with Ina and its pals - if any - might be radiogenic argon rather than water. 

For more on Ina-like features, see:

Braden, S.E., Stopar, J.D., Robinson, M.S., Lawrence, S.J., Van Der Bogert, C.H. and Hiesinger, H., 2014. Evidence for basaltic volcanism on the Moon within the past 100 million years. Nature Geoscience, 7(11), pp.787-791.




Offline Warren Platts

Short answer: lunar water is only going to affect lunar architectures.  If NASA decides to go to Mars, the simplest way to get there is a straight line that bypasses Luna.  It'll be useful for lunar colonies and ascending from Luna, but not much beyond Cislunar space; it's more fuel conservative otherwise to avoid the lunar gravity well for missions beyond Earth.

It depends on how much and on how cheaply rocket fuel could be delivered to L2 Lagrange point. The L2 point is an ideal place to top off fuel tanks for a journey to Mars. No one is proposing to launch a Mars mission from the surface of the Moon. Check out this MTV:



This is from one of the older ULA papers. It would take 847 tonnes of rocket propellant. It could carry 16 people with a single stage delta v of like 11 km/s. This could cut the transit time by half over a Hohmann transfer, all fully propulsively--no need for a fancy aerocapture system. Alternatively, it could do a round-trip on a single fill-up using Hohmann transfers if there was no refueling capability at Mars. Liquid hydrogen is the best radiation shielding we know of. What's not to love about it?

Well, number one I guess, is that it's inconceivable that that much propellant could be moved from Earth's surface to the L2 point. It'd take over 50 Falcon Heavy launches to get that much propellant up there. But it wouldn't be that big of a deal for a small fleet of single-stage, lunar tanker-landers to get that much propellant up there.
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Offline savuporo

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Re: Impact of lunar free water on Exploration Architecture
« Reply #13 on: 05/22/2016 10:54 PM »
As for heterogeneous distributions, that's also what I'm saying: you can't just drill anywhere and expect to hit water. The lunar glasses examined so far show water concentrations on the order of MORBs, that is around 0.2% (2,000 ppm). These may be the driest oceanic basalts; basalts associated with mantle plume hot spots tend to be significantly wetter. There is no evidence I'm aware of that the lunar samples so far examined have came from hotspot locations. Lunar hotspot plumes could have water contents on the order of 1% or more. These are the areas we should be looking at for exploration purposes IMO.
Meanwhile, PSRs are theorized to contain 1-10% wt water in surface layer regolith - in areas that are identifiable from a combination of orbital observations. In a region where constantly solar powered operations could be possible, because of permanently sunlit peaks - and the feasibility of utilizing any of the lunar resources depends primarily on the available energy source required for processing, anyway.

Although certainly valuable and interesting, I don't see why should this shift the primary focus away from polar volatile research .
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Offline Lar

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Re: Impact of lunar free water on Exploration Architecture
« Reply #14 on: 05/22/2016 11:09 PM »
This possibility that water can be found 20-80 km down with luck is fascinating, but I'm with savopuro... if we are trying to decide how to bootstrap up, using polar volatiles first seems like it would be less effort than drilling a long ways into the crust, especially if poor understanding will lead to dry holes. That sounds like it would be hard to do in early days.

So why not exploit polar ice first? Use the water to in part power industrialization and exploration of the moon.  Over time the moon will be well enough mapped and understood and there will be enough facilities and materiel present that doing drilling will be less risk, since if it is a dry hole, we haven't lost nearly as much time and effort (and used up as much landed mass) proportionately....
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Offline savuporo

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Re: Impact of lunar free water on Exploration Architecture
« Reply #15 on: 05/22/2016 11:26 PM »
BTW, European Lunar Symposium just concluded couple days ago.

Plenty of interesting talks and papers:
http://els2016.arc.nasa.gov/downloads/ELS_2016_Program_1.9.pdf
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Offline the_other_Doug

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Re: Impact of lunar free water on Exploration Architecture
« Reply #16 on: 05/22/2016 11:39 PM »
Short answer: lunar water is only going to affect lunar architectures.  If NASA decides to go to Mars, the simplest way to get there is a straight line that bypasses Luna.  It'll be useful for lunar colonies and ascending from Luna, but not much beyond Cislunar space; it's more fuel conservative otherwise to avoid the lunar gravity well for missions beyond Earth.

It depends on how much and on how cheaply rocket fuel could be delivered to L2 Lagrange point. The L2 point is an ideal place to top off fuel tanks for a journey to Mars. No one is proposing to launch a Mars mission from the surface of the Moon...

Yeah -- the current NASA DRA (Design Reference Architecture) for landing humans on Mars involves setting up a cislunar infrastructure and basically putting the stack for Mars transit together at EML-1 or EML-2.

It doesn't specifically call for refueling options from lunar resources, but a lot of the side-talk around this relatively recent update to the DRA includes talk (and some studies) around "encouraging" third parties to develop lunar resource fuel generation (basically, processing lunar water into LH2 and LOX) and providing these fuels to the cislunar infrastructure.

I think it might be interesting, and would definitely be possible, to see, for example, Orbital/ATK or SpaceX bid on a contract to provide lunar-resource fuels, and the next humans on the Moon could be industrial workers, not explorers or scientists, there simply to set up a refining plant.  If it turns out that such a plant can more easily be located at Ina-D rather than Shackleton, well, more power to y'all... :)
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Offline savuporo

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Re: Impact of lunar free water on Exploration Architecture
« Reply #17 on: 05/22/2016 11:56 PM »
It doesn't specifically call for refueling options from lunar resources, but a lot of the side-talk around this relatively recent update to the DRA includes talk (and some studies) around "encouraging" third parties to develop lunar resource fuel generation (basically, processing lunar water into LH2 and LOX) and providing these fuels to the cislunar infrastructure.

There is a huge, enormous gap going from talking about 100-2000 ppm molecule concentrations in possible minerals to a refueling rockets from industrial scale refineries.

Notice how there is no design reference architecture for any kind of ISRU operation anywhere, apart from 1% scale model MOXIE that might fly four or six years from now.
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Offline Warren Platts

"The conventional wisdom that the Moon is virtually anhydrous has been overturned."

1. I would prefer to say it has been slightly adjusted.  A little bit of water, not a lot.

"the canonical surface feature thought to be formed by an outgassing event(s) is the Ina D-caldera that happens to be perched atop a low shield volcano at the intersection of two major rille systems."

2. It might be on a shield volcano, but that's only one interpretation of the topography. 

3. It's not a caldera. 

4. It certainly is not at the intersection of two major rille systems. 

5. Also we now have lots of Ina-like objects, some which actually are associated with volcanic domes (near Cauchy) and an ancient caldera rim (west of Tobias Mayer) - so other Ina-like features make that case better than Ina does. 

6. Lastly, the volatiles associated with Ina and its pals - if any - might be radiogenic argon rather than water. 

7. For more on Ina-like features, see:

Braden, S.E., Stopar, J.D., Robinson, M.S., Lawrence, S.J., Van Der Bogert, C.H. and Hiesinger, H., 2014. Evidence for basaltic volcanism on the Moon within the past 100 million years. Nature Geoscience, 7(11), pp.787-791.

Phil! Great to hear from you! Thank you for taking the time to post here! :D

Taking your points in order:

1. It's all relative. 6 billion tonnes of water could launch a space shuttle every day for 200,000 years. We're not looking for Waterworld--we just want to launch some spacecraft.

2. Serpentinization of olivine can also form a dome... But whatever it is, it's gotta be something special because we don't see these things everywhere.

3. I agree it's not a true caldera. That's just the name that's been handed to us by history. Sort of like the Sea of Tranquility is not a true sea. (Also, compare google searches of "Ina" vs. "D-caldera" ;) )

4. I was basing that statement on Schultz et al.'s (2006) paper. I'll quote the relevant paragraph in full:

Quote from: Schultz et al.
Ina is just one of at least four similar endogenic features, most related to a system of west-northwest–east-southeast (WNW–ESE)-trending rilles around the Imbrium impact basin. Ina is at the intersection of northeast–southwest-trending structural elements (radial to Imbrium) and subtle WNW–ESE-trending regional structural elements crossing the Imbrium ejecta. The Hyginus depression is similarly situated at the intersection of the two rilles (Rima Hyginus): a northwest–southeast graben extending to the northwest, and an eastnortheast–west-southwest (ENE–WSW) graben to the southwest, which parallels an adjacent en echelon system of rilles (Rima Ariadaeus). Another small irregular depression in Mare Tranquilitatis near the crater Arago also occurs along an extension of the ENE–WSW (Rima Ariadaeus) system where it intersects a different set of rilles. These occurrences in similar structural settings indicate that volatiles (for example, juvenileCO2 and evenH2O) trapped deep within the Moon episodically escape along crustal weaknesses, thereby continually freshening the regolith.

You know more about the lunar geography than I do, Phil, so I'll happily defer to your statement. So it's at the intersection of two "structural elements" that are not true rilles. Still, Schultz's (and my) larger point is that these objects seem to be associated with "crustal weaknesses" that provide an avenue for volatile movements to near surface depths.

5. OK, the paper you linked to has 70 such features listed in the supplementary information section (uploaded below). A a while back you gave a list of 41 such features (also attached below if that's OK with you). It seems that while there is some overlap, there are ones you have listed that Braden et al. do not have. Is that right? Also, I would like to plot all of these features on a map of the Moon, but the only thing I've got is Google Moon, and it's pretty low res. Is there some other relatively accesible lunar GIS system that you would recommend to use instead?

6. As for argon, that's really hard to believe. I know Arlin Crotts wrote a bit about that, but Ar forms super-gradually. It's hard to see how the pressure could build up enough to cause a maar-like explosion. Alternatively, I guess pressure could build up in pore spaces at deep levels to close to lithostatic pressures. Once it was released, I guess you could get a prolonged jet that could blow off the regolith. However, even if it is argon, rather than H2O that is responsible for their formation, that would still be a valuable resource perhaps, since Ar would make a good fuel for ion-propulsion engines.

7. Thanks for the link. I have a few issues with the paper. (1) They say the smooth deposits "superpose" the rough ones, and while they are certainly higher elevation, just by looking at the color photos, the rough terrain is younger (at least defined in terms of exposure to space) than the smooth deposits. (2) they think the smooth deposits are lava flows, but if that were the case, the (a) they'd be fresher than the rough terrain, (b) there should be cracks and vents visible, (c) the edges of the lobes are too steep to have formed from a flowing liquid. (3) They cite the Schultz paper (2006) that argues for the outgassing theory, but do not criticize it or otherwise discuss outgassing.

When I look at profiles of the smooth lobes, what they remind me of are picnic tables that have received a fresh snowfall. The picture I see is of jets blowing regolith up, and regolith falling back into areas of the pit where the jets are not going. I see an initial explosion, followed by gas jets, or geyser-like episodic gas releases that could form the smooth lobes. Thus the rough terrain (where the jets emit from) would have a very fresh appearance, but the smooth lobes would have an intermediate aged appearance because it would be a mixture of regolith, some of which had been exposed to space weathering for a long time, other parts not so much.

Then there's the issue of nomenclature again. I agree they shouldn't be called "calderas". You, Phil, coined the term "meniscus hollows" because the smooth lobes look sort of like mercury menisci. I called them "rimless pits" above in a post to show a purported link to the rimless pits of Mercury that they at least superficially resemble. I kind of want to call them  "lunar maars" because I think that's the best Earth analog that they resemble. So what do you recommend Phil?

For more on Ina-like features, see:

Braden, S.E., Stopar, J.D., Robinson, M.S., Lawrence, S.J., Van Der Bogert, C.H. and Hiesinger, H., 2014. Evidence for basaltic volcanism on the Moon within the past 100 million years. Nature Geoscience, 7(11), pp.787-791.
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Offline nadreck



1. It's all relative. 6 billion tonnes of water could launch a space shuttle every day for 200,000 years. We're not looking for Waterworld--we just want to launch some spacecraft.



NO the arithmetic critic in my brain just hates the sound of fingernails on chalkboard:

Rough count:  6,000,000,000t water = 750,000,000t H2 / 106t = ~7,000,000 launches or ~20,000 years at one a day


Polar volatiles are the way to go for early bootstrapping - note that on Earth drilling to a practical limit for exploitive purposes (oil/natural gas) is 10,000 meters and that requires the most massive 3 stand drill rigs, thousands of tons of steel drill pipe and 6 months of elapsed time with a motor rated at thousands of horsepower (meaning you need more than a mega watt of solar power on the moon. And all that for a single test hole maybe 40cm in diameter.

As for the economics of shipping propellant made from lunar volatiles to LEO, if you assume two different designs of tanker craft: LEO to EM-L2 (which if designed to use Aerobraking might need only 300m/s of ΔV at full load and 3.5km/s to return the craft) and Lunar surface to EM-L2 (Full ΔV 2.5km/s, and maybe 2.6km/s to return). Then every kilo of propellant transferred to LEO might represent as little as 3kg of propellant  launched from the surface and about 4.5kg of water processed into propellant.


EDIT oops mixed units in the last sentence, they should all be the same mass units so the ratio of mass of water extracted to propellant mass destined for LEO is 4.5 to 1 and the ratio for propellant launched from the moon to arrived at LEO leaving enough for the craft to return is 3 to 1
« Last Edit: 05/23/2016 01:33 AM by nadreck »
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

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