Extinct nuclides in and chronology of the early solar system
• Can extinct nuclides be used for chronology?
• Were extinct nuclides distributed homogeneously in the solar system?
• How were extinct nuclides produced?– Solar or nucleo-synthetic?
• Al-Mg, Fe-Ni, Ca-K, Be-B and Mn-Cr
New developments of Al-Mg systematics
• Half life =0.73 Ma• Canonical value of the initial 26Al/27Al for CAIs (C
a-Al-rich Inclusion = refractory inclusion) was 5x10-5.
• SIMS (high spatial resolution)
– Internal isochron for chondrules• MC-ICPMS (high precision, low spatial resolution)
– Bulk CAIs– Internal isochron for CAIs– Bulk chondrules
Summary of Al-Mg
• CAIs formed with initial 26Al/27Al ratios as high as 6.5x10-5.
• The canonical value (5x10-5) is probably due to resetting of anorthite. (measured by SIMS)
• High temperatures in CAI forming region continued ~300,000 years.
• Chondrule precursors are as old as CAIs.
• Chondrule formation continued ~2 Ma.
Half life of 60Fe is 1.5 Ma.60Fe is not produced by solar cosmic ray.
60Fe has to be injected from a nearby supernova.
Fe-Ni systematicsauthors samples age from CAI initial 60Fe/ 56Fe solar system initial
T exp BBirck & Lugmair, 1988 CAI 0Ma 1.6+/ -0.5 x 10-6 1.6+/ -0.5 x 10 -6 nucleosynthetic?
Shukolyukov & Lugmair, 1993 eucrite(CK) Mn-Cr 4.4Ma 4-7.5 x 10-9 3.2-6.0 x 10 -8 disturbed?
Shukolyukov & Lugmair, 1993 eucrite(J uv) Mn-Cr 5.5Ma 4.3 x 10 -10 6 x 10 -9 disturbed?
Kita et al., 1998 ureilite U-Pb 5Ma <1.8 x 10 -7 <1.8 x 10 -6
Kita et al., 2000 chondrule Al-Mg 1.7Ma <1.4 x 10 -7 <3.4 x 10 -7
Tachibana & Huss, 2003 sulfide in chondrites ~2Ma 1.1-1.7 x 10 -7 2.8-4.5 x 10 -7 disturbed?
Moustefaoui et al., 2003 sulfide in chondrite ~2Ma7.5+/ -2.6 x 10 -71.9 +/ - 0.7 x 10 -6 disturbed?
Tachibana et al., 2005 pyroxene in chondrules ~2Ma 2-5 x 10 -7 5-12 x 10 -7
Quitte et al., 2005 eucrites(J uv and Bo) Hf-W 19.4Ma 5.6 x 10-10 4.4 x 10 -6 disturbed?
This study olivine in angrite Mn-Cr 5Ma <6.5 x 10-9 <6.5 x 10-8
60Fe in the early solar system
10-10
10-9
10-8
10-7
10-6
10-5
0 5 10 15 20
initial 6
0 Fe/
56Fe
Age from CAI (Ma)
CAI
eucrite
eucrite
eucrite
ureilite
sulfide
sulfide
chondrule
chondrule
60Fe in the early solar system
angrite
Decay curve
summary on 60Fe
• 60Fe is produced by supernova, but not produced by solar cosmic ray. Therefore, it is very important for understanding origins of short-lived nuclides.
• 60Fe seems to be present in the early solar system, but the distribution may have been heterogeneous.
41Ca
• Half life of 41Ca is 0.15 Ma.• Nearly constant initial ratios of 41Ca/40Ca ~1.4x10-8
are observed for CAIs with 26Al. • If 41Ca is absent, 26Al is also absent.
– FUN (fractionation & unknown nuclear component) inclusions
• This was explained by a late injection model. But now that CAI formation seems to have continued for 300,000 years, there seems to be a problem.
Late injection model:41Ca and 26Al
0
2
4
6
8
10
0 0.2 0.4 0.6 0.8 1 1.2
what you get from a late injection model
injection41Ca26Al
injection rate and radiogenic species
(arbitrary units)
Time (Ma)
FUN normal CAI
10Be (half life =1.5 Ma) produced by cosmic ray
• Abundant 10Be in CAIs was initially considered to be produced by solar cosmic ray.
• However, it was later shown that it may be GCR 10Be trapped in cores of molecular clouds.(Desch, 2003)
• FUN inclusions contain 10Be and do not contain 26Al.• Normal CAIs contain both 10Be and 26Al.
– Solar cosmic ray scenario• Fun inclusions are evaporation residues irradiated by solar cosmic ray?
• Normal CAIs are condensates getting the 10Be and 26Al from the irradiated nebula?
– Galactic cosmic ray scenario• Fun inclusions are evaporation residues or condensates formed before inject
ion of 26Al?
• Normal inclusions are condensates formed after injection of 26Al?
53Mn-53Cr, half-life = 3.7 Ma
• Suitable for studying planetary processes• Initial ratios of 53Mn/55Mn in CAIs are not w
ell established.• Recently, comparison with Al-Mg and Pb-P
b ages became possible for eucrites and angrites.– Previously such comparison was made for chon
drites but was not conclusive.
High initial Mn ratios for CAIs are inconsistent with Al-Mg system and could be due to heterogeneity of the nebula or due to distur
bed Mn-Cr system
Papanastassiou et al., 2005
Age comparisonAl-Mg, Mn-Cr and Pb-Pb ages
CAI, eucrite and angrites
CAI T Asuka881394 T LEW86010
26Al/ 27Al 5.00E-05 3.9Ma 1.26E-06 - -
53Mn/ 55Mn - - 4.30E-06 6.6Ma 1.25E-06
Pb/ Pb (Ma) 4567.2+/ -0.6 2.2Ma 4565+/ -0.9 7.2Ma 4557.8+/ -0.5
CAI T D'Orbigny & S99555 T LEW86010
26Al/ 27Al 5.00E-05 5.1Ma 4.00E-07 - -
53Mn/ 55Mn - - 3.00E-06 4.7Ma 1.25E-06
Pb/ Pb (Ma) 4567.2+/ -0.6 ? 4557.8+/ -0.5
Summary on Mn-Cr and comparison
• Al-Mg and Mn-Cr systems can be used as chronometers.
• Absolute ages of CAIs are probably ~4568Ma.
conclusions
• Can extinct nuclides be used for chronology?– Probably yes: 10Be, 26Al (excluding FUN), 53Mn (excl
uding CAIs)– Not sure: 41Ca, 60Fe
• How were extinct nuclides produced?– Because of 60Fe, nucleo-synthetic origin seems more l
ikely than SCR origin.– But, the late injection model need closer examination.
Al-Mg ages of CAIs (Bizzarro et al., 2004)
MC-ICP-MS of bulk CAIsThe initial 26Al/27Al ratio is 6.0x10-5 if equilibrium fractionation law is used.
Angrite (error bars are one sigma.)
6.9
7
7.1
7.2
7.3
7.4
7.5
0 1 105 2 105 3 105 4 105 5 105
S99555 isochron
60Ni/62 Ni
57Fe/62Ni
60Fe/56Fe <6.5x 10-9 (2)
More on 10Be
• So far, internal isochron for the first 1~3 Ma is made only with Al-Mg system.Thus, cannot be cross-calibrated.– e.g.dating of chondrules.– Mn-Cr cannot be used because the initial in CA
Is are strange.
• 10Be seems to be hopeful.