[meteorite-list] Water in space

From: MexicoDoug_at_aol.com <MexicoDoug_at_meteoritecentral.com>
Date: Wed Jun 1 06:30:56 2005
Message-ID: <213.1e8877b.2fcee854_at_aol.com>

Tracy L. wrote:
>Exactly! Consider the case of copper carbonate. In its hydrated form,
>it is a pretty blue crystal; we used to use it in our swimming hole in
>low amounts to kill off algae and weeds. In its anhydrous form, it's
>a greenish powder. Don't eat either one; bad. I'm not akamai enough
>to guess what hydrates might be present in meteorites, but I'm pretty
>sure this is what is meant by water being present in meteorites,
>chemically bound into various minerals, which may be released by
>heating or chemical reaction.

A-Hola Tracy, Hmmmm. The idea that a hydrate is a great way to stabilize
water I totally agree with you and the physics of it, so I follow there. But:
 
I think you are confusing copper sulfate (pretty hue, light royal blue
crystals) with copper carbonate and/or copper carbonate hydroxide minerals.
Copper carbonate does not form a hydrated complex in a chemical sense, though
copper carbonate hydroxide might be loosely called "hydrated" instead of a
hydroxide, by some fast talking pool chemical salesman (or mystic jewelry peddler?)
at local pool store if it is really sold there (?). Anyway, a hydroxide is
a different chemical animal than a hydrated complex containing water which is
bound by weaker structural or van der waals types of attraction: that to
which I think Chris eluded and of main interest here for water are
chemical/structural "hydrates".

That chemical hydrated compound on your mind would likely be Copper Sulfate,
wouldn't it? It forms a pentahydrate = complex with 5 water molecules per
Copper/Sulfur. The Copper carbonate might be an undesirable precipitate in
the swimming hole produced from interaction of copper sulfate with lime or
disolved carbon dioxide I bet, and it might be a yucky green?

Copper Sulfate (a.k.a., synthetic chalcanthite) is a beautiful lab example
of a stable hydrated complex to at least +150 C. It is quite possible it
could appear in trace quantities in meteorites, so you are not far off at all if
we deal with CuSo4*5H20 !!

However, the more common hydrated (i.e., bound water) reservoirs found in
some meteorites I found in the literature based on your contemplation of not
even guessing, would be a suite of clay minerals, which can result from the
aqueous modification ("weathering") products of feldspars and pyroxenes, common
meteoritic stock. That is the same kinds of clay that expands when you mix
it with water and can be formed into shapes...i.e., hydrated clay - well not
all Clays hydrate, but plenty do.

Clay minerals are very complicated beasts that still cause all kinds of
trouble even regarding nomenclature to say what is what, since their structures
vary so much, simply being a woven backbone pattern of silicates and
hydroxides and a variety of candidate cations/metals, and ambiguous formulae something
like (Ca,Na,H)(Al,Mg,Fe,Zn)2(Si,Al)4O10(OH)2*n(H2O) in the case of
smectites, which can form widely variable laminar sheets which suck up water between
them better than silica gel! Unlike copper sulfate, slight changes in
temperature and humidity can reverberate by changing their structures, formula, and
most importantly, amount of bound water - even getting a density is hard, let
alone a positive compositional ID. So that is why you can't do too much
better than "clay minerals". The two best tests are a taste test and messy
Separation-Xray analysis. And that would seem to be the variable/flexible nature
of much of the bound water in not-too-shocked-and-baked meteoroids for s/he
who wants to really do some bonding with them...

For chondrites, here are some of those hydrated beasts that serve as space
oasises (that has a nice ring to it):

Type 3: phyllosilicates, principally smectites and micas, serpentine
associated with ferrihydrite.
Type 2: Smectites (rare in the CM2s, abundant in the CR2s), Abundant
serpentines (with extremely variable compositions and structures), Mg-Fe sulfates,
tochilinite-serpentine intergrowths and carbonates.
Type 1: Saponite + (Serpentine)

Taken from an impressive face-off of Zolensky and Bischoff in Maui at:
WORKSHOP ON PARENT-BODY AND NEBULAR MODIFICATION OF CHONDRITIC MATERIALS
(preliminary program)
June 17, 1997, Maui, Hawai'i
http://www.lpi.usra.edu/meetings/chondrite/pdf/program.pdf

I chose the Zolensky writeup not because I don't believe the other competing
 theories (I am a Bischoff fan), but rather because of the enumeration of
minerals he did including some clay and other hydrate-ables. The documentation
is:
AQUEOUS ALTERATION OF CARBONACEOUS CHONDRITES: EVIDENCE FOR ASTEROIDAL
ALTERATION. M. E. Zolensky, Mail Code SN2, NASA Johnson Space Center,
Houston TX 77058, USA.

Wish to have been a fly for three days on the hotel wall in Maui then,
Aloha, Doug
 
Received on Wed 01 Jun 2005 06:30:44 AM PDT