[extropy-chat] Water Marks the Asthenosphere

Eugen Leitl eugen at leitl.org
Fri Jan 26 20:23:50 UTC 2007

On Fri, Jan 26, 2007 at 07:43:14AM -0500, Technotranscendence wrote:

> Yes.  I was wondering about the absolute amounts...  On another list, I
> wrote:  "Of course, this doesn't mean that, e.g., you might be able to
> easily use or release this water.  My first thought was, of course,

About the only use for lunar volatiles is fuel and closed-loop ecosystems.
Both are questionable. Plasma thrusters are much preferrable, once you're
orbiting, and linear motors (maglev) can throw things into orbit
using just electrons, which are recycled after each shot.

> imagine flushing it out [on a body like Mars].  But my quick follow-up
> was: how and what would that do to the mantle?"

You're talking geology, I'm talking industry and colonization. 
> Yes, that might be so, but what if it's not?  Is there enough data on

I would be very surprised, given that Moon was completely molten after 
formation, and it can't even hold volatiles in the current state. It's
surface is what we down here call UHV, and it takes baked-out stainless
apparatus, turbovacs and cryotraps to come close. (Of course, once you
start cranking seriously, you've got industrial pollution: HV instead of
UHV, at least regionally. Lunar flora/fauna wept & shriveled up).

> the lunar interior to know?  If large amounts of water can be
> incorporated into Earth's mantle and not baked out, might not something
> similar be true about Luna?  Of course, it could be that the water in

Why do you need that much water?

> Earth's mantle can't be baked out because the only place it has to go -- 
> up -- has been saturated with water -- and also because there are
> processes to add water to the mantle (so that if there's a loss, there's
> some balance that maintains a stable equilibrium or the loss is so low
> that huge amounts still remain).

I somehow sense that Amara will shortly have a word with you.
> I've read about something like this a few years ago in _American
> Scientist_.  However, it remains speculative and the process mentioned

Of course it's speculative, but at least we have detector data, which
might or might coincide with protons.

> could happen anywhere on the Moon -- not just in the polar regions.  If

You can only catch vapor in a permanently shadowed lunar crater, which
is a reasonable approximation of a cryptrap lined with chemisorbent.
During two weeks of lunar night the temperature drops (-181C, as compared
to -233C in polar crater shadow), but the regolith layer is thin, and daytime 
temperatures are brutal (+123C in UHV is baking-out brutal), so it
*will* achieve escape velocity soon after sunrise.

> the mixing were sufficient to put water lower enough or the mineral
> binding tight enough (olivine would capture lots of water, wouldn't it)
> so that the temperatures it's likely to experience later on wouldn't be
> able to get it out, it might be there in lots of places -- not just the
> poles.  I think the article set some limits on the degree to which this

I think we'd be lucky to find some at the poles, but of course we'll take
anything we'll find anywhere.

> would happen and set a depth of about a meter or so for such mixes.

Regolith layer on the surface is few cm thick at best, dunno about craters.

> Since you mention protons, wasn't there also talking about recovering
> solar wind hydrogen, though the amounts would be very small, from lunar
> regolith?

If you bake it hard enough, it will come out as water, regardless what
it is. (It might be dirty water, at least in polar deposits, but that's
actually a plus, since ammonia gives you fertilizer, and H2S is easy
enough to remove).
> Colonization or for industrial and other processes that need water.

I question the wisdom of colonisation. As to industrial, most industrial
processes which are aquatic can be restated in other terms that fit
high insolation and UHV conditions, and they will even work much better
typically. As for the rest of them, closed-loop processes are our friends.
> This is possible, though I would prefer to hedge my bets.  Some here

Absolutely -- but you will first need to send teleoperated machinery to
the Moon, whether you like it, or not. This is no longer time of
foolishness in multiple percent of large country GNP (I've seen the
budget allocation trend for the US today renderend in nice animated 
Java (by way of http://my.reddit.com ), and it's depressing).

> argued against sending a probe to Pluto because, by 2015, better, faster
> craft would beat it there.  Well, 2015 hasn't arrived yet, but what if

It takes some 15 years to plan a mission, and if you never start with it,
you will never launch one. Same thing with planning Beowulf clusters --
waiting is always the best option, unless you have a deadline. What is
Pluto worth us? If I look at the above mentioned budget allocation trend,
I could cry you a river.

> 2015 looks a lot like 2007 -- save for higher storage hard drives, a few
> more genomes being mapped, and nanotube TVs?

Some things get worse, actually, such as launch costs (prior to Shuttle),
how many tons a single-package to LEO costs, and whether it can include
a nuclear reactor. Propulsion options are really limited in deep space,
and chemical propulsion translates in huge payloads we nowadays are unwilling/
unable to launch.

Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
ICBM: 48.07100, 11.36820            http://www.ativel.com
8B29F6BE: 099D 78BA 2FD3 B014 B08A  7779 75B0 2443 8B29 F6BE
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