J/ApJ/743/L23 48Ca heterogeneity in differentiated meteorites (Chen+, 2011)
48Ca heterogeneity in differentiated meteorites.
Chen H.-W., Lee T., Lee D.-C., Shen J.J.-S., Chen J.-C.
<Astrophys. J., 743, L23 (2011)>
=2011ApJ...743L..23C 2011ApJ...743L..23C
ADC_Keywords: Solar system ; Abundances
Keywords: meteorites, meteors, meteoroids - nuclear reactions, nucleosynthesis,
abundances
Abstract:
Isotopic heterogeneities of 48Ca have been found in numerous bulk
meteorites that are correlated with 50Ti and 54Cr anomalies among
differentiated planetary bodies, and the results suggest that a rare
subset of neutron-rich Type Ia supernova (nSN Ia) was responsible for
contributing these neutron-rich iron-group isotopes into the solar
system (SS). The heterogeneity of these isotopes found in
differentiated meteorites indicates that the isotopic compositions of
the bulk SS are not uniform, and there are significant amounts of nSNe
Ia dust incompletely mixed with the rest of SS materials during
planetary formation. Combined with the data of now-extinct short-lived
nuclide 60Fe, which can be produced more efficiently from an nSN Ia
than a Type II supernova ejecta, the observed planetary-scale isotopic
heterogeneity probably reflects a late input of stellar dust grains
with neutron-rich nuclear statistical equilibrium nuclides into the
early SS.
Description:
We separated approximately 1mg of Ca by conventional cation ion
exchange column chemistry (Tera et al. 1970GeCAS...1.1637T 1970GeCAS...1.1637T; Russell et
al. 1978GeCoA..42.1075R 1978GeCoA..42.1075R) from each dissolved 1-2g whole rock sample
residue left over from the W isotopic measurement (Lee et al.
2009E&PSL.288..611L 2009E&PSL.288..611L). Roughly ∼2ug of Ca was loaded onto an outgassed
Re filament for Ca isotope measurement using the Triton, a thermal
ionization mass spectrometry, at the Institute of Earth Sciences
(IES). A double filament technique was used to obtain a Ca+ ion
current around 0.2-0.5nA and >1.5nA for two separate static runs to
measure sequentially from mass 40Ca to 44Ca and 42Ca to 48Ca
for about 1000 and 2000s, respectively.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 87 90 Ca isotopic composition of bulk differentiated
meteorites, a terrestrial plagioclase, and a
man-made 48Ca enriched standard
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Type Meteor type (3)
13- 41 A29 --- Name Meteor name (1)
43- 47 F5.2 10-4 40Ca ? Abundance of 40Ca (2)
49- 52 F4.2 10-4 e_40Ca ? The 2σ uncertainty in 40Ca (2)
54- 58 F5.2 10-4 43Ca Abundance of 43Ca (2)
60- 63 F4.2 10-4 e_43Ca The 2σ uncertainty in 43Ca (2)
65- 70 F6.2 10-4 46Ca Abundance of 46Ca (2)
72- 76 F5.2 10-4 e_46Ca The 2σ uncertainty in 46Ca (2)
78- 82 F5.2 10-4 48Ca Abundance of 48Ca (2)
84- 87 F4.2 10-4 e_48Ca The 2σ uncertainty in 48Ca (2)
--------------------------------------------------------------------------------
Note (1): All meteoritic and terrestrial samples were run several times to
calculate their mean and uncertainty of repeated measurements. The
48Ca enriched standard is the gravimetric mixture of NIST SRM915a
standard with 48Ca spike to have a 1.3 epsilon units (in parts in
1e4) of enrichment and there were 3 individual measurements list here.
Note (2): Abundance deficits in part per 10,000 relative to NIST SRM915a
iCa=[(iCa/44Ca)S/(iCa/44Ca)N-1]x1e4 (indices are
S=sample, and N=NIST SRM915a). All measurements are normalized to
42Ca/44Ca=0.31221 (Russell et al. 1978GeCoA..42.1075R 1978GeCoA..42.1075R) to correct
the fractionation effects. Blanks values indicate the abundances was
not determined during analysis.
Note (3): one of Angrites, Diogenites, Eucrites, Man-made, Mars,
Terrestrial, or Ureilites
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 22-May-2013