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(meteorobs) Excerpts from "CCNet 12/2002 - 21 January 2002"
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From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet: THE SKY IS FALLING? NO SWEAT
Date: Mon, 21 Jan 2002 11:27:01 -0000
CCNet 12/2002 - 21 January 2002
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[...]
(5) SUGAR-SWEET METEORITES
G. Cooper et al.
(6) ORIGINS OF INTERPLANETARY DUST
M. Aleon et al.
[...]
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(5) SUGAR-SWEET METEORITES
Cooper G, Kimmich N, Belisle W, Sarinana J, Brabham K, Garrel L:
Carbonaceous meteorites as a source of sugar-related organic compounds for
the early Earth
NATURE 414 (6866): 879-883 DEC 20 2001
The much-studied Murchison meteorite is generally used as the standard
reference for organic compounds in extraterrestrial material. Amino acids
and other organic compounds(1) important in contemporary biochemistry are
thought to have been delivered to the early Earth by asteroids and comets,
where they may have played a role in the origin of life(2-4).
Polyhydroxylated compounds (polyols) such as sugars, sugar alcohols and
sugar acids are vital to all known lifeforms-they are components of nucleic
acids (RNA, DNA), cell membranes and also act as energy sources. But there
has hitherto been no conclusive evidence for the existence of polyols in
meteorites, leaving a gap in our understanding of the origins of
biologically important organic compounds on Earth. Here we report that a
variety of polyols are present in, and indigenous to, the Murchison and
Murray meteorites in amounts comparable to amino acids. Analyses of water
extracts indicate that extraterrestrial processes including photolysis and
formaldehyde chemistry could account for the observed compounds. We conclude
from this that polyols were present on the early Earth and therefore at
least available for incorporation into the first forms of life.
KeyWords Plus:
MURCHISON METEORITE, MASS SPECTROMETRY, DERIVATIVES, EVOLUTION, ACIDS
Addresses:
Cooper G, NASA, Ames Res Ctr, Moffett Field, CA 94035 USA
NASA, Ames Res Ctr, Moffett Field, CA 94035 USA
Univ G DAnnunzio, IRSPS, I-65127 Pescara, Italy
Copyright ) 2002 Institute for Scientific Information
===========
(6) ORIGINS OF INTERPLANETARY DUST
Aleon M, Engrand C, Robert F, Chaussidon M: Clues to the origin of
interplanetary dust particles from the isotopic study of their
hydrogen-bearing phases
GEOCHIMICA ET COSMOCHIMICA ACTA 65 (23): 4399-4412 DEC 2001
Ion microprobe quantitative imaging was performed for H, D, C-12.13,
O-16.18, Al-27 Si-28,Si-29,Si-30 and in five stratospheric particles with a
1.5 X 1.5 mum spatial resolution to determine the carriers of high D/H
ratios and to give new clues about the parent bodies of interplanetary dust
particles (IDPs). Among these particles, four appear to be of
extraterrestrial origin. Using imaging, the large variations of D/H ratios
can be correlated at the micrometer scale with chemical composition so that
endmembers can be identified. From the systematics of variation of C/H and
D/H ratios, water present as hydroxyls in phyllosilicates (at C/H = 0) and
three different types of organic matter (OM1, 2, and 3) were identified.
Water exhibits D/H ratios lying in the chondritic domain (D/H similar to 150
X 10(-6)), whereas OMs are enriched in deuterium. OM1 is similar to the
macromolecular organic matter of carbonaceous chondrites (D/H = 250 X 10(-6)
and C/H = 1.5). OM2 (D/H = 1500 X 10(-6) and C/H = 1.0) is close to cometary
HCN.OM3 (D/H = 2000 X 10(-6) and C/H = 3.0) is a highly condensed
carbonaceous phase with no counterpart in known extraterrestrial objects.
The C, O, and Si isotopic compositions are solar within +/- 10%.
The identification of these phases allows a better understanding of the
origin of D/H variations inferred for the protosolar nebula. The only
mechanism that can explain such high D/H ratios is interstellar chemistry.
However, D/H ratios in interplanetary dust organic matter remain lower than
those measured in molecules from cold molecular clouds. This difference can
be accounted for by an isotopic exchange with liquid water in IDP parent
bodies. In addition, the close association of the chondritic component OM1
with the likely cometary component OM2 is evidence for a link between
carbonaceous chondrites and comets. Although IDPs contain cometary organic
matter, the water-D/H ratio is lower than that measured in comets (310 X
10(-6)). IDPs seem thus constituted of various materials formed over a large
range of heliocentric distances. Copyright (C) 2001 Elsevier Science Ltd.
Addresses:
Aleon M, Univ Calif Los Angeles, Dept Earth & Space Sci, 595 Charles Young
Dr, Los Angeles, CA 90095 USA
CNRS, Ctr Rech Petrog & Geochim, F-54501 Vandoeuvre Les Nancy, France
Ctr Spectrometrie Nucl & Spectrometrie Masse, F-91405 Orsay, France
Museum Natl Hist Nat, CNRS, URA736, Lab Mineral, F-75005 Paris, France
Copyright ) 2002 Institute for Scientific Information
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