constraints on conditions in the solar nebula from the laboratory study of presolar grains
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Constraints on Conditions in the Solar Nebula from the Laboratory Study of Presolar Grains. Gary R. Huss Hawai’i Institute of Geophysics and Planetology University of Hawai’i at Manoa. Silicon Carbide. Hibonite (CaAl 12 O 19 ). Young stellar systems in Orion. - PowerPoint PPT PresentationTRANSCRIPT
Constraints on Conditions in the Solar Nebula from the Laboratory Study of Presolar Grains
Gary R. HussHawai’i Institute of Geophysics and Planetology
University of Hawai’i at Manoa
Silicon Carbide Hibonite (CaAl12O19)
Young stellar systems in Orion
Chondritic Meteorites preserve material from the Solar Nebula
Types of Presolar GrainsName Composition Size AbundanceDiamond C 1-2 nm 1500 ppmSilicon Carbide SiC 0.1-10 m 10-15 ppmGraphite C 0.1-20 m 5-10 ppmTiC, MoC, ZrC, RuC, FeC, Fe-Ni
Inside other materials
1-25 nm n.d.
Si3N4 Si3N4 1-5 m 1-20 ppbForsterite Mg2SiO4 0.2-0.5 m 10-1800 ppmEnstatite MgSiO3 0.2-0.5 mAmorphous Silicate variable 0.2-0.5 m 20-3600 ppmSpinel MgAl2O4 0.1-20 m 1.2 ppmCorundum Al2O3 0.2-3 m 100 ppbHibonite CaAl12O19 1-5 m 20 ppbTiO2 TiO2 n.d. <10 ppbD-rich organics HCNO n.d. n.d.
CI Chondrites: Representative Samples of Molecular Cloud?
• Chemical composition matches Sun
• High abundances of presolar grains
• Severely altered on parent body
CI
(ppm) Diamond SiC Graphite Spinel Al2O3 Silicate (%) Presolar
C 34500 1400 4.2 10 4*
Mg 98900 0.21 2000 2
Al 8680 0.46 0.059 6e-3
Si 106400 9.8 1295 1.2
Ca 9280 1e-4 1e-6
Fe 190400 543 0.3
Fraction of Primitive Chondritic MaterialDirectly Traceable to Molecular Cloud
*Plus unknown amount of interstellar organic compounds.
Constraints on Presolar Carbon in CI from Diamond Abundance
• Hard lower limit: ISM carbon is 20% diamond (Allamandola et al., 1993)
• Reasonable LL: ISM carbon is 4-5% diamond
• Upper limit: major fraction of MC organic material destroyed; other elements unfractionated
5432100
20
40
60
80
100
Percentage of Diamond in CI Carbon
How much of CI chondrites came directly from molecular cloud material?
• Bulk composition implies little chemical fraction-ation and little addition of fractionated material– Evidence for small addition of high-T material (≤5%)
• High abundances of most presolar grains• High percentage of carbon may be presolar
– Large fraction may have been destroyed• High percentage of other elements also presolar
– Complete evaporation and recondensation destroys presolar grains
~90% of CI material from molecular cloud.
Presolar Materials as Tracers of Nebular and Parent Body Processing
Component Thermal Stability Chemical Resistance
Diamond P3 Low High
Diamond HL High High
Diamond P6 Very High High
Silicon Carbide Moderate High
Graphite Low Moderate
Al2O3, Spinel Very High High
Silicates Low to High Low to Moderate
Effects of Metamorphism on Abundances of Presolar Materials
• Abundances of all types decrease with increasing metamorphic grade
• Rate of decrease related to chemical and thermal resistance of materials
All started with the same mixture
LL Chondrites
• Lithophile elements more refractory than Na are unfractionated
• Volatile elements depleted• Refractory presolar components unfractionated• Thermally sensitive presolar components depleted
LL3 Chondrites
1
3
0.1
1
10
Ave LL3 Semarkona (LL3.0)
Decreasing Volatility
ZnSe
BrSb
NaGa
KAs
MnAu
CrFe
MgCo
NiV
CaLa
SmEu
YbLu
RuIr
AlOs
CO Chondrites
• Elements more refractory than Au unfractionated (except for addition of CAIs)
• Volatile elements depleted• Presolar components fractionated• Resistant components enriched relative to CI
0.1 0.01
0.1
1
CO3 Chondrites
1
ALHA 77307 (CO3.0)
ZnSe
BrSb
NaGa
KAs
MnAu
CrFe
MgCo
NiV
CaLa
SmEu
YbLu
RuIr
AlOs
Decreasing Volatility
CR Chondrites
• Elements more refractory than Cr unfractionated• Volatile elements depleted• Presolar components more steeply fractionated• Resistant components enriched relative to CI
0.1 0.01
1
0.1
1
CR2 Chondrites
Ave CR2Renazzo
Decreasing Volatility
ZnSe
BrSb
NaGa
KAs
MnAu
CrFe
MgCo
NiV
CaLa
SmEu
YbLu
RuIr
AlOs
LL3 Chondrites
1
3
0.1
1
10
Ave LL3 Semarkona (LL3.0)
Decreasing Volatility
ZnSe
BrSb
NaGa
KAs
MnAu
CrFe
MgCo
NiV
CaLa
SmEu
YbLu
RuIr
AlOs0.1 0.01
0.1
1
CO3 Chondrites
1
ALHA 77307 (CO3.0)
ZnSe
BrSb
NaGa
KAs
MnAu
CrFe
MgCo
NiV
CaLa
SmEu
YbLu
RuIr
AlOs
Decreasing Volatility0.1 0.01
1
0.1
1
CR2 Chondrites
Ave CR2Renazzo
Decreasing Volatility
ZnSe
BrSb
NaGa
KAs
MnAu
CrFe
MgCo
NiV
CaLa
SmEu
YbLu
RuIr
AlOs
Crystalline Silicates: Astronomical Observations
• Crystalline silicates are rare in the interstellar medium.
• Crystalline silicates are more abundant in protostellar disks.
• Abundance of crystalline silicates higher near protostar.
Crystalline silicates form in protostellar disks.
Matrix of ALHA 77307
From Brearley 1993, GCA 57, 1521
• Molecular cloud material survives in chondrites
• Its survival depends on structure and composition
• Presolar grains are keys to understanding early solar system processes