Re: Interplanetary dust particles: reproducing GEMS-like structure in the laboratory (Forwarded)

Jonathan Silverlight wrote:
In message <1140700976.647088.34640@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, John
Curtis <john@xxxxxxxxx> writes
Andrew Yee wrote:

The varied
compositions of the GEMS make it difficult to arrive at a consensus
regarding their origin and formation process.

The glassy substance in GEMS is forsterite, Mg2SiO4. The SiO4
portion, as well as the entire salt, requires water for its formation.
Si* + 4 H2O ---> H4SiO4 (silicic acid) + 2 H2

A very small amount of web searching will show you that forsterite can
form via solid phase reactions.
"It is presumed that the formation of forsterite proceeds according to
the solid phase reaction: 2MgO+SiO2 -> Mg2 SiO4"
<http://www.freepatentsonline.com/6899768.html>
or gas phase
"Let us consider the formation of forsterite (Mg2SiO4) from the gas
phase in. a thermodynamic equilibrium state."
<http://www.ita.uni-heidelberg.de/~gail/prepr/dalg-rev.ps>

Formation of an oxyanion such as silicate (SiO4) without using
water is a challenge. Formation of Mg salt of said oxyanion without
usig water is a double challenge.
This extra effort is not really necessary because the atmospheres
of late-type stars are awash with water:
http://www.edpsciences.org/articles/aa/pdf/2001/34/aade292.pdf?access=ok
John Curtis

.

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