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Presolar Silicates
Presolar Silicates in meteorites
in Primitive Chondrites
K. Nagashima,
S. Kobayashi,
N. Sakamoto,
永島一秀,
小林幸雄,
坂本直哉, 殿谷梓,
圦本尚義
東工大・地球惑星科学
A. Tonotani,
and H. Yurimoto
Earth and Planetary Sciences,
Tokyo Institute of Technology
Mar. 02, 2005
Presolar grains
26Al
12C, 18O
Supernova ejecta
16 O
Solar System
Meteorite
28Si
Onion-type structure of
massive star before supernova
1µm
Stellar outflow
AGB star (source of s-process nuclides)
SiC from Murchison
(Amari et al., 1994)
Presolar grains
Diamond
SiC
Graphite
Spinel
Corundum
Silicate
0.001
0.01
0.1
1
10
100
1000
ppm
10000
are susceptible
to aqueous
It Silicates
was about
a year ago
that alteration,
which transformed silicates into hydrous silicates.
elusive This
presolar
first
discovered.
processsilicates
erases anywere
presolar
isotopic
signatures.
Nagashima et al., 2004; Nguyen and Zinner, 2004;
Difficulties to locate presolar
silicates
among
boundlessly abundant
Mostefaoui
and Hoppe,
2004
solar system silicates that are major constituents of meteorites.
Analytical methods
• Isotope microscope (Yurimoto et al., 2003)
Secondary Ion Mass Spectrometry: SIMS
+
2-D ion detector: SCAPS
Isotope
ims-1270
ESAMicroscopeMagnetic
Sector
SIMS
SCAPS
SCAPS
sample
10 mm
Spatial resolution of isotope image
Sample
name of chondrite
Acfer 094
pristine
class
C3-ungrouped
Yamato-81025
CO3.0
ALHA 77307
CO3.0
Adelaide
altered Murchison
C3-ungrouped
CM2
BSE
17O
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ǙDZÇÃÉsÉNÉ`ÉÉǾå©ÇÈÇ…ÇÕïKóvÇ­Ç•
ÅB
Adelaide (ungrouped)
16O
18O
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ǙDZÇÃÉsÉNÉ`ÉÉǾå©ÇÈÇ…ÇÕïKóvÇ­Ç•
ÅB
28Si /16O
BSE
d18O
d17O
(‰)
(‰)
Oxygen Isotopic Ratios
of Presolar Silicates
A total of 41 presolar
silicates were found.
BSE Images of Presolar Silicates
Olivine
Pyroxene
Olivine
from Acfer 094 (ungrouped)
1µm
from Adelaide (ungrouped)
1µm
BSE Images of Presolar Silicates
from Acfer 094 (ungrouped)
1µm
from Murchison (CM2)
GEMS?
(Glass with Embedded Metal and Sulfide)
1µm
Grain size distribution of presolar silicates
20
number
15
10
5
0
0
200
400
600
size / nm
800
1000
Note that unidentified silicates
are not included.
Nagashima et al., 2004; Nguyen and Zinner, 2004; Mostefaoui et al., 2004;
Messenger et al., 2003; 2004; Floss and Stadermann, 2004; this study
Origins
(after Nittler et al., 1997)
Group 1
O-rich RGB or AGB
Group 2
AGB with Cool Bottom
Processing
Group 3
low-metallicity RGB or AGB
Group 4
still uncertain origin
low-mass AGB?
supernovae?
altered
pristine
Abundances of presolar silicates in meteorites
number of
abundance
presolar silicates
(ppm)
meteorite
class
Acfer 094
C3-ungrouped
4
Yamato-81025
CO3
20
ALHA 77307
CO3
8
Adelaide
C3-ungrouped
5
10
50
30
40
Murchison
CM2
4
3
Abundances of presolar silicates
Interplanetary Dust Particles (IDPs)
450 ~5500 ppm
(Messenger et al., 2003; Floss and Stadermann, 2004)
Destruction of presolar silicates
by thermal processing in the solar nebula.
Most pristine chondrites
10~50 ppm
Destruction of presolar silicates
by aqueous alterations on chondrite parent body.
Aqueously altered chondrites
<3 ppm
Summary
In situ isotopic survey of matrix materials in primitive chondrites are
conducted.
A total of 41 presolar silicates are identified in 5 chondrites.
Most of presolar silicates are enriched in 17O, suggesting origins in
O-rich RGB/AGB stars.
Estimated abundances of presolar silicates in primitive chondrites
are 1~50 ppm.
The difference of abundances of presolar silicates between IDPs
and primitive chondrites could be explained by destruction of
presolar silicates by thermal processing in the solar nebula, and
aqueous alteration processes on their parent bodies.
Future work
Further studies conducted on different meteorite types will allow us
to understand more detailed origins and history of presolar grains,
conditions in solar system environments.
Search for new types of presolar silicate grains such as grains from
supernovae.