Tagilski meteorite turned out to be alkaline

Canadian geochemists analyzed the fragments
Tagilskogo
meteorite
method
atom probe tomography and
found that particles
magnetite in its structure was formed
in an alkaline environment.
These
results well
explain
the predominance of L-forms
for some amino acids previously
found in the meteorite
the transition between D – and
L-forms
in alkaline medium proceeds much faster than
in acidic or neutral. Results
research published
in the journal
Proceedings
of the National Academy of Sciences.

In the morning
18
January 2000
ice Tagilskogo lake on
Northern British Columbia
a meteorite fell. Drop
saw many local
residents
so
a large part of the debris collected during
several days. Thanks
this
efficiency (as well as extremely
a good
place
drop) fragments of the meteorite reached
scientists, not having to dirty the earth impurities
— on
today Tagilski
the meteorite is considered one of the most
clean
meteorites.

Tagilski
a meteor (or meteorite Tagilskogo lake) is
of carbonaceous chondrite silicate
material interspersed with small
particles of coal, graphite, and various
iron compounds (mainly
magnetite Fe3O4).
In addition
it had traces
various
amino acids
— composite
parts
proteins that
can
to serve as source material for
chemical
evolution. The study of the meteorite has shown that the formation of
these
complex molecules
occurred inside of a meteorite in
small splashes of water inside
silicate matrix.
Curious
what
one
of the four
discovered
amino acids — alanine, were
in the form of a racemate, equivalent to a mixture
two
optical isomers — D
and
L
form.
At the same time two
other
amino acids
glutamic
and aspartic
— was
discovered mainly in the form of
L-forms.
Scientists
suggested
this following explanation:
in
the solution of both forms of D
and
L
are
in equilibrium, and
can pass into one another.
Aspartic
and glutamic
aminokisloty
mainly
kristallizuetsya in the form
L-shape,
so
to a solution of L-shape
constantly
is the disadvantage, and balance
biased towards her education. In
a result, the crystals accumulate in
mostly
L-shape,
while in the liquid phase concentration
D – and
L-forms
about
equal. In
the case of alanine is a difference between
the formation of crystals there, so
the number of D – and L-forms
remain
equal and in the solid phase and in liquid.

It
explanation said
canadian geochemists
under the leadership of Richard
Nicklin (Richard I. Nicklin) and
Lee white (Lee F. White) from the Department of natural history Royal
Ontario Museum. They took a few
small
pellets
magnetite
sizes from 10 to 50 microns
and analyzed them by the method
atom probe tomography, which
allows to obtain a 3D image
material with atomic resolution. It turned out that
surface
grains of magnetite
there are
blotches of alkaline and
alkaline earth metals

basically it is sodium, also caught the calcium and
magnesium.
Metals
penetrated into the particles of magnetite to a depth of
approximately 30 nanometers, forming a small
agglomerates with a size of about 10 nanometers.
This
the surface could be formed in
slightly alkaline
environment
(modeling conducted by scientists, indicates the range of pH 7 to 10).

This
the result is well
clarifies
earlier
proposed
the mechanism of the transition of amino acids in L-form.
In this
and other
works modeling
the transition
different amino acid
enantiomers
each other, the authors
believed environment
neutral
or slightly acidic.
In alkaline
environment
the transition between different enantiomers
flows
fast, the
there is a solution for faster return
from a lack of L-shape
the racemate — equivalent ratio
of the two forms.
This
by the way, a new study shows
that environment
inside
the meteorite was
even more favorable for the accumulation
L-shape
amino acids than expected
the company informed.

In addition
from the obtained data it is possible to do
the conclusion about the concentrations of organic and
nitrogen-containing substances in
parent
celestial body, from which calved
meteorite.
Case
that alkaline
environment
overall a very
favorable
for the synthesis of amino acids. In
Tagilskom the same meteorite
the contents
amino acids low (less than 1
ppm, at the time, as, for example,
in similar composition of the Murchison field reservoir
meteorite
the contents
there were about 60 ppm).
If
even in such
favorable
conditions
amino acids turned out a little,
the reason is probably
was
the lack
other key components
for example, aldehydes or ammonia.

Chemical
composition
meteorites — a source of valuable information
not only about space,
but also about the history of the Earth.
For example,
after examining the surface of ancient micrometeorites,
scientists have found out,
at the time of their fall (2.7 billion
years ago) the atmosphere of our
planet
approximately 70 per cent consisted of
carbon dioxide

Natalia Samoylova

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