Radial Mixing in the Early Solar System: Meteoritic and Cometary Evidence

Radial Mixing in the Early Solar System: Meteoritic and Cometary Evidence

Planet Formation and Evolution: The Solar System and Extrasolar Planets Tübingen 1.-6.3.2009

M. Trieloff University of Heidelberg, Institute of Geosciences, Heidelberg, Germany


Astrophysical evidence: Observations of protoplanetary discs (extrasolar)

Cometary evidence (early solar system):Hale Bopp (IR observations)Wild-2 dust returned by STARDUST (laboratory analyses)

Meteoritic evidence (early solar system asteroids):Flash heated objects in chondrites: Chondrules and calcium,aluminum rich inclusions (CAIs)

IR spectroscopy of protoplanetary disks: Mg silicates olivine+pyroxene –crystalline fraction higher in inner disks (van Boekel et al. 2004)

40 +- 20% 15 +- 10%

55 +- 25% 10 +- 5%

95 +- 10% 40 +- 15%

Crystalline fractions in some outer disks considerable, similar to solar system cometscomets(Wooden et al., 2000)

Dust processing in disks and radial mixing into outer disks

IR spectroscopy of protoplanetary disks: Mg silicates olivine+pyroxene –crystalline fraction higher in inner disks (van Boekel et al. 2004)

10 +- 5%

40 +- 20%

55 +- 25%

95 +- 10%

Refractory forsterite grain from STARDUST collector

Silicates (Olv, Px, Fs), glass, Fe-Ni sulfide, refractory minerals (An,Di,Sp), CAI: Inti

No phyllosilicates and carbonates in Wild-2 particles

CAI „Inti“

Cometary grains from comet Wild-2 returned by the STARDUST mission





Indicator:High temperatureprocessing (crystallinity,refractory rich)

Meteorites: Fragments of small bodies in the solar system, the asteroids between Mars and Jupiter

Inferred number of parent bodies is >100 (accretion to full-sized planet inhibited by early Jupiter?!)

Innisfree

Carbonaceous chondrites (CI, CM, CV, CO, …): (mild thermal/aqueous metamorphism)

• Ca,Al-rich inclusions

• Chondrules

AllendeAllende

• Fine grained matrix (volatile rich)

undifferentiated, e.g. preaccretional structures preserved

undifferentiated, e.g. ‘cosmic’ Fe,Ni abundance

<900 K

1800-2000 K

1400-1600 K

Metal abundance of chondrites: Origin from primitive, undifferentiated parent bodiesVariation of oxidation state and metal abundance: Origin from compositionally different parent asteroids

0,0 0,2 0,4 0,6 0,8 1,00,0

0,2

0,4

0,6

0,8

1,0

Solar total iron

EL

(Fe silicate +sulfide

/Si)CI

CI/CM

EH

EL

Ordinary chondrites: H: high FeL: Low FeLL: Low total, low metallic Fe

Enstatite chondrites

Carbonaceous chondrites: named after main memberCI (Ivuna)CM (Mighei)CV (Vigarano)CO (Ornans)






High temperature processing of chondrules and CAIs: indicative of radial mixing?

Nuth (2001)

… some models assume the answer is YES

… what about (abundant) chondrules?… fast cooling (100-2000 K / hour; e.g. former melt glass)… local flash heating (shock, lightning, planetary

collisions) in the asteroid belt region?… do chronology and chemical complementarity

allow large scale movements?

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30

Si [wt%]

Mg [wt%]

CV3 Efremovka

matrix

chondrules

enstatite(intermediate Mg)

forsterite(high Mg)

solarMg/Si-ratio

solarMg-, Si-composition

Chemical complementarity of chondrules and matrix in CV chondrites:Exemplified by Mg and Si (J. Wood, P. Bland, H. Palme)

Chemical complementarity of chondrules and matrix in CR chondrites:Exemplified by Mg and Si (J. Wood, P. Bland, H. Palme)

Matrix and chondrules of specific chondrites formed from Mg/Si= solar precursor material, and were not separated (e.g. by radial drift) before chondrite accretion growth timescales short when compared to radial drift timescales

0,04 0,06 0,08 0,10 0,120,6

0,7

0,8

0,9

1,0

1,1

Solar

EH

ELRLLL

H

CRCI

COCM

CK CV

Mg/Si

Al/Si

Earth´s mantle

[% chondrules]

0

401520

3755

CV chondrules

CV matrix

CR matrix

CR chondrules

What about isotope chronology of chondrule formation?

• Ca,Al-rich inclusions

• Chondrules

4567.2± 0.6 Ma (U-Pb-Pb, CV Efremovka; Amelin et al., 2002)

AllendeAllende

4564.7± 0.6 Ma (CR Acfer059; Amelin et al., 2002)

2-3 Ma age difference supported by 26Al-26Mg chronometry

Short-lived nuclides in the early solar system and their half-lives:

26Al 26Mg (0.72 Ma)129I 129Xe (16 Ma)182Hf 182W (9 Ma)53Mn 53Cr (3.7 Ma)244Pu fission (80 Ma) 10Be 10B (1.5 Ma) 41Ca 41K (0.1 Ma) 60Fe 60Ni (1.5 Ma)

… nucleosynthesis in mass-rich stars

… or nuclear reactions due to solar irradiation (10Be)

Trapezium (Orion nebula)

... injected into protoplanetary disks (solar mass)

Radiometric dating Planetesimal heating

5

4

3

2

1

0

L type

CR type

CO type (Kurahashi et al. 2007)

CO type (Kunihiro et al. 2004)

LL type

Chondrule

26

Al-26

Mg ages (Ma after CAIs)

26Al as tool for radiometric dating:26Al-26Mg ages of individual chondrules of different chondritic parent bodies (Kita, Nagahara, Russell, Mostefaoui etc.)

26Al as planetesimal heat source: Extent of heating as a function of 26Al content and accretion time after CAIs

0 1 2 3 40

1

2

3

4

Melting and partial meltingof planetesimals formed within 1,9 Ma

CO (Tmax

=870 K )(Kurahashi et al. 2007)

CR (Tmax

=670 K )

CO (Tmax

=870 K )(Kunihiro et al. 2004)

L (Tmax

=1220 K )

Mean chondrule

26

Al-26

Mg ages (Ma after CAIs)

Parent body formation age predicted by 26Al heating (Ma after CAIs)

LL (Tmax

=1220 K)

Mean 26Al-26Mg ages of chondrules of different chondritic parent bodies correlate with heating degree of parent bodies: stronger heated planetesimals have earlier formed chondrule populations






High temperature processing of chondrules: indicative of radial mixing?

High temperature processing of CAIs: indicative of radial mixing?

NO (only possible if fast movement with micron dust)

Fassait (Ti-rich diopside)

Anorthite

Zoned type B1 CAI from Leoville (CV)

Melilite

from: Davis & Richter 2005

Fe-Ni-metal

Enstatite – MgSiO3

Forsterite – Mg2SiO4

Gehlenite Ca2Al2SiO7

Hibonite CaAl12O19

AnorthiteFra

ctio

n C

I ch

ond

riti

c co

mp

osit

ion

con

den

sed

Cpx

Albite

Spl

Condensation sequence of minerals in a cooling solar nebula: Ca,Al minerals important high temperature condensates

CAIs and refractory inclusions:

Rare (0.1% - 13%)Carrier of 16O enrichment in carbonaceous chondritesSlower cooling than chondrules (10 K / hour)Resided 2-4 Ma in solar nebulaIndependent chemical component









Good candidates

Conclusions:

High degree of crystallinity or high temperature processing is not a compelling proof of radial mixing

High temperature processing of CAIs suggests radial outward transport in solar nebula, but reasoning requires broad body of evidence

Future modeling needs to evaluate different mechanisms (meridional flows, etc.) and must check for element fractionations






Good candidates

Radial Mixing in the Early Solar System: Meteoritic and Cometary Evidence

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