Abundances of the Elements – Solar, Meteoritic, and Outside the Solar System

Why are we interested in the abundances of the elements?

Constitution of (baryonic) matter, quantities of stable elements/isotopes

Formation of the solar systemComposition of the solar system, planetary compositions

Origin of the elementsAbundance distributions are critical tests for nucleosynthesis models

Katharina Lodders, Washington University Saint Louis, USA

Abundances of the Elements – Solar, Meteoritic, and Outside the Solar System

Solar abundances: present-day observable composition of Sun, mainly photosphere, but also sun spots, solar flares, solar wind

Solar system abundances: composition at time of solar system formationISM/ molecular cloud composition 4.6 Ga agoproto-solar abundancesLi, D, short-lived radioactive nuclides (26Al, 129I), long-lived (=still present) radioactive nuclides (87Rb, 235U, 238U, 232Th)

Cosmic abundances: this term should be avoidedmany stars similar in composition as Sun,amount of elements heavier than He (=metallicity) changes with time

there is no “generic” cosmic composition abundances vary across Milky Way Galaxy, other galaxies

Concentration and Abundance

Concentration: Quantifies amount of mass or number of particles per unit mass or unit volume

Concentration by mass (or weight): g of element per 100 g sample = percentg of element per ton (106 g) = ppm = parts per million

10,000 ppm = 1 mass% e.g., CI chondrite analysis gives 18.28 g Fe per 100 g sample

Fe concentration is 18.28% by mass

Concentration by number:number of particles per unit volume

e.g., number of O2 molecules in air20.95% of air molecules are molecular O2

at room T and P, there are ~2.5×1019 particles/cm3

so there are 2.5×1019×20.95/100 = 5.2×1018 (molecules O2)/cm3

Abundance is a relative quantityAbundance Scales and NotationsMost commonly used: Atoms by number, NNormalized to a reference element

Astronomical abundance scale: normalized to H, the most-abundant element in universeH = 1012 atoms converted to log scale: A(H) = log H = 12

abundances are measured relative to H, e.g.,N(Fe)/N(H)log Fe = log { N(Fe)/N(H) } + 12

used for H-rich systems: stars, ISM

Cosmochemical abundance scale:normalized to Si, the most abundant cation in rock, N(Si) = 106 atoms

used for planetary modeling, meteorites

Coupling the scales:

Derivation of elemental and isotopic abundances

Earth crustMeteorites

Other solar system objects, gas-giant planets, comets, meteors

Solar photospheric spectrum, SW, SEP

Spectra of other dwarf stars (B stars)Interstellar mediumH II regionsPlanetary Nebulae (PN)Galactic Cosmic Rays (GCR)

Also presolar grains

Start with Earth’s crust & meteorites

in 1847 (Elie de Beaumont)

~59 out of 83 elements known at the time spectral analysis invented later (1860s)Mendeleev’s periodic table later (1869)

There are 16 abundant elements common to different crustal rocks, mineral & ocean waters, organic matter, and meteorites:

H, Na, K, Mg, Ca, Al, C, Si, N, P, O, S, F, Cl, Mn, Fe

Light elements with atomic masses up to Fe are abundant, heavier elements than Fe are rare

Notable exceptions Li, B, Be

Gluconium =Be, Didymium=Nd+Pr, Columbium=Nb

Abundances in igneous rocks

(Table IX, col. II of Harkins 1917)

Atomic Numbers

6 8 10 12 14 16 18 20 22 24 26 28

Wei

gh

t Per

cen

t

0

10

20

30

40

50

C

O

F

Na

Mg

Al

Si

P S Cl

KCa

TiCr

Fe

Ni

What controls the abundances of the elements?Abundances of the elements as a function of atomic number

Earth crust, igneous rocks Clarke 1898, Harkins 1917

Quantitative analyses limited to abundant elements in rocks

no discernable trends of abundance with atomic number or atomic weight

Abundances are modified from solar during Earth’s formation and differentiation

Derivation of elemental abundances

Earth’s crust:- available material that can be analyzed in the lab- but not representative for composition of entire Earth

Earth is also not representative for solar system composition

Chemical and physical fractionations during(1) formation of planetesimals from molecular cloud material processed in the protoplanetary accretion disk (solar nebula)

(2) differentiation of Earth materials into core, silicate mantle and crustelements follow geochemical charactersiderophile elements: metallic elements into core

Fe, Ni, Co, Au, Ir, Pt-group elements, …lithophile elements: oxide and silicate rock-forming elements

go into silicate mantle and crustMg, Si, Al, Ca, Ti, REE…

Crust preferentially contains elements with large ionic radii that enter silicate melts during differentiation: Si, Al, Ca, K, Na, REE, …

(incompatible in silicate mantle minerals olivine, pyroxene)

redgiants super

novaedust

presolar molecular cloud

proto-Sun &solar nebula

gas giant protoplanetsbegin to form

evaporation & recondensation

of dust

primitive planetesimals chondrite parent bodies

recondensedsilicatemetalsulfide

agglomeration

accretion,planetesimalgrowth

preservedpresolar

dust

differentiatedplanetesimals

ironsachondrites

break-up

terrestrialplanets

crust formationbasaltic volcanism

largeimpactsmetallic core

formation duringheating

Molecular cloud composition 4.6 billion years ago = solar system composition

Earth crust today

H

Zi Be B C N O F

Na Mg Al Si P S Cl

K Ca Sc Ti V Cn Mn Fe Co Ni Cu

(Cu) Zn Ga As Se Br

Rb Sr Yt Zr Nb Mo Ru Rh Pt Ag

(Ag) Cd In Sn Sb Te I -

Cs Ba La Ce -

Er - Ta W - Os - Ir - Pt - Au -

(Au) - Hg Tl - Pb Bi

Th - U

?

?

? ? ?

?

- ?

Di

Elementsdetectedin celestialbodies

Elementsnot detectedin celestialbodies

Presence ofelements isvery uncertain

Presence ofelementsis uncertain

Sign Convention:

I.A. Kleiber's tableon the chemical

compositionof celestial bodies

1885

Extend search for chemical elements to other celestial objects(Kleiber 1885; 68 elements out of 83 are known)

Earth’s crustmeteoritesCometsMeteorsSunOther stars

Composition of celestial objects is not random

Helium found in 1868 but not plotted by Kleiber, no other noble gases known at the time

ABUNDANCE OF THE ELEMENTS

(stony meteorites; Harkins 1917)

Atomic Numbers

6 8 10 12 14 16 18 20 22 24 26 28

We

igh

t P

erc

en

t

0

10

20

30

40

C

O

Na

Mg

Al

Si

P

S

K

Ca

Ti Cr

Fe

Co

Ni

Abundances vs. atomic number 1917:

Harkins 1917

Use average abundances from meteorites, no photospheric abundances yet

Even-numbered elements are more abundant than their odd-numbered neighbors

Li, B, Be low in abundancesC low because of volatility, but still more abundant than odd numbered neighbors B or N

Fe peak

Abundances of elements heavier than Fe (Z > 26) are quite low

Harkins’ discovery graph of the odd-even effect in elemental abundances

Odd-Even distribution of the elements as a function of atomic number is also seen for heavy elements

Good example: rare earth elements (REE)Similar geochemical behavior

Odd-even abundance effect not (completely) erased during re-distribution of REE among minerals in rocks

Figure updated from Goldschmidt 1937Normalized to Y= 100 atoms (Y not shown)

Russell

Rare Earth Minerals Goldschmidt & Thomassen, 1924

10

20

30

Sun's Atmosphere Russell 1929

as of 2007

20

40

60

80

Shales (sedimentary rocks)

Minami, June 1935

20

40

60

80

Meteoritic Stones I. Noddack, Nov. 1935

CI-chondrites as of 2003

0

10

20

30

La Pr Pm Eu Tb Ho Tm LuCe Nd Sm Gd Dy Er Yb

MeteoritesChondrites: most common types of meteoritesMixtures of silicates, metal and sulfides that may have been processed subsequently on their parent asteroids

primitive planetesimals chondrite parent bodies

recondensedsilicatemetalsulfide

agglomeration

accretion,planetesimalgrowth

preservedpresolar

dust

differentiatedplanetesimals

ironsachondrites

break-up

terrestrialplanets

crust formationbasaltic volcanism

largeimpactsmetallic core

formation duringheating

Achondrites and iron meteorites: experienced melting and/or extensive re-crystallization on their parent asteroids

Kodaikanal meteoriteFound 1898, 15.9 kg, IIE iron, fine octahedrite with silicate inclusions

Pho

to C

hris

tian

Ang

er 2

006

Specimen shown from Natural History Museum Vienna

A 3.5 kg sample is at the Geological Survey India, Calcutta

Chondritic Meteorites

Chondrites: contain mineral phases that most closely resemble the original solids that were present in the solar nebula

Many types of chondrites contain round silicate spheres called chondrules

Chondrite groups: Ordinary chondrites: H, L, LL Enstatite chondrites: EH, EL Carbonaceous chondrites: CI, CM, CV, CO, CK, CR, CH

Bjurboele L/LL3 chondrite Chondrules in the Tieschitz ordinary chondrite

Ph

oto

: L

e M

usé

um

Na

tion

al d

'His

toire

Na

ture

lle,

Pa

ris

Abundances of CI chondrites give the best match to elemental abundances in the Sun(except for volatile elements H, C, N, O, noble gases)

“CI” for carbonaceous chondrite of Ivuna type

5 observed CI chondrite falls: Alais 1806 (6 kg), Ivuna 1938 (0.7 kg), Orgueil 1864 (14 kg), Revelstoke 1965 (1 g), Tonk 1911 (10 g)

Orgueil meteorite

CI chondrites - do not contain chondrules- their minerals are aqueously altered hydrous silicates, salts- metal and sulfide are oxidized

Secondary mineral alterations did not change overall elemental composition.CI chondrites contain the highest amount of volatile elements when compared to other chondrites

Ordinary chondrite:

CV chondrite:

50% condensation temperature, K, at 10-4 bar

40060080010001200140016001800

con

cen

trat

ion

ratio

CM

ch

on./

CI c

hon

.

0.0

0.5

1.0

1.5

2.0

Li

Be

B

Al

P

S

Cl

K

CaSc

Cr

Mn

Ni

Ge BrRb

Zr

Nb

Mo

Ru

Pd

Ag

Cd

Sn

Sb

Te ICs

Ba

CePr

EuTm

Yb

Hf

Ta

W

Os

Ir

PtAu

TlBi

U

volatility trend in CM chondrites

lithophilesiderophilechalcophilehalogen

In

F

Pb

FeMg Si

Re

Ti

Gd

Co

Sr Rh

VThY

SeZn

Ga

As

Cu

Na

Independent of geochemical character

50% condensation temperature, K, at 10-4 bar

40060080010001200140016001800

conc

entr

atio

n ra

tio C

V c

hon.

/CI c

hon.

0.0

0.5

1.0

1.5

2.0

Li

B

Na

Al

Si

P

SCl

K

Ca

Sc

Ti

V

Cr

Mn

Ni

Cu

Ga

Ge

As

Rb

Y

Zr

Nb

Mo Ru

Rh Pd

Ag CdSb

Cs

BaLa

PrEu

Gd

YbLuHf

W

Re

Os

Ir

Pt

Au

TlPbBi

Th

U

volatility trend in CV chondrites

lithophilesiderophilechalcophilehalogen In

BrTe Se

FSn

ZnI

Fe

Mg

Be

SrCe

Co

Independent of geochemical character

50% condensation temperature, K, at 10-4 bar

40060080010001200140016001800

conc

ent

ratio

n ra

tio H

cho

n./C

I cho

n.

0.01

0.1

1

BF

NaMg

Al P

S

Cl

KCa V CrMn

CuGa

Ge

As

Se

Br

Rb

Zr

Ag

Cd

In

Sn

Sb

TeI

Cs

Ba

EuYbHf

WReOs Pt Au

Tl

Pb

Bi

U

volatility trend in H chondrites

lithophilesiderophilechalcophilehalogen

Zn

F

FePd LiBe

Si

Ce

CoNiIr Ru

SrThMg

Rh

NbTa

MoScY

REE

Ti

Independent of geochemical character

H He Li Be B C N O F NeNaMgAl Si P S Cl Ar K CaSc Ti V CrMnFeCoNiCuZnGaGeAsSe

abun

danc

e (a

tom

s/10

0 F

e)

1e-7

1e-6

1e-5

1e-4

1e-3

1e-2

1e-1

1e+0

1e+1

1e+2

1e+3

1e+4

1e+5

1e+6

1e+7

Halley dust CI chon photosp. Taurid Geminid Perseid CometWild2 Wild2 resi

Abundances in the photosphere, CI chondrites, meteors, and cometary samples

Comet Halley data: Schultze et al, Jessberger et al; Comet Wild 2 data from Flynn et al. 2006

mass distribution in thesolar system

mas

s%

0.00000001

0.0000001

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

100

Su

n

Mer

cury M

ars

Ven

us

Ear

th Jup

iter

Ura

nu

s

Nep

tun

e

Sat

urn

Plu

to

Eri

s

Cer

es

Sun holds more than 99% ofthe solar system’s mass

Composition of Sun should be good approximation for solar system as a whole

Element determinations in the Sun~66 elements out of 83 naturally occurring elements identified in photosphere

all stable elements up to atomic number 83 (Bi) plus radioactive Th and U

~30 – 35 elements well determined in photosphere

Determined in photosphere with larger uncertainties: > 0.10 dex: (factor 1.3) Li, Be, B, N, Sc, Cr, Ni, Zn, Ga, Rh, Cd, In, Nd, Tb, Ho, Tm, Yb, Lu, Os, Pt > 0.05 dex: (factor 1.12) Mg, Al, Si, Ti, Fe, Co, Nb, Ru, Ba, Ce, Pr, Dy, Er, Hf, Pb

Difficult to determine (line blends, low abundance)Ag, In, Sn, Sb, W, Au, Th, U As, Se, Br, Te I, Cs, Ta, Re, Hg, Bi

Detected but difficult to quantify from spectra: He, Ne, Ar, Kr, Xe found in solar wind

Determined from Sun-spot spectra, relatively uncertain: F, Cl, Tl

Challenges for photospheric determinations:

Line list for neutral atoms, ions, excited state transitionsFe several thousand lines, other elements only 1 line accessible

Line blendingNi and Fe lines interfere; e.g., determinations of O, Th

Transition probabilities and lifetimes of atomic statesrecent re-analysis of transition metals and REE

Atmospheric modelscontinuum modeling (e.g., UV for Be)LTE vs. non LTE, is radiation in local equilibrium with matter2D, 3Dgranulation, convection

He abundanceDetermined from helioseismic models and solar evolution models that must match the current luminosity and radius of the Sun

One input to models is ratio of mass fraction of H ( = X) to mass fraction of heavy elements (= Z)Mass fraction of He ( = Y) follows from X + Y + Z = 1

Z is the sum of the mass fraction of all elements heavier than He (the “metals”) Z is dominated by C, N, O, Ne (CNO ~66%, CNONe ~75%)

Ratio of Z/X is uniquely defined, convert mass fraction of He to atomic abundance

Problem: New lower C, N, O photospheric abundances (Allende Prieto et al., Asplund)give a lower mass fraction of metals

Lower C, N, O abundances reduce opacity which is needed to obtain agreement of solar evolution models with observations

Possible solution: Increase the Ne abundanceto increase opacity in sun’s interior (Bahcall)

But solar Ne abundance is also derived indirectly, e.g., from Ne/O ratio in SWLower O also lower Ne

“Solar” Ne abundance needs to be worked out

Solar Ar abundance

CI-chondrites; Si = 106 atoms

10-5 10-4 10-3 10-2 10-1 100 101 102 103 104 105 106 107 108

sola

r ph

oto

sphe

re;

Si =

106

ato

ms

10-3

10-2

10-1

100

101

102

103

104

105

106

107

108

109

1010

1011

H

He.

LiBe

B

C

N

O

F

Ne

Na

Mg

Al

Si

P

S

Cl

Ar

K

Ca

Sc

Ti

V

CrMn

Fe

Co

Ni

CuZn

Ga

GeKr

RbSr

YZr

Nb

MoRu

Rh

PdCdSn

Sb

Xe Ba

La

Ce

Pr

Nd

Sm

Eu

Gd

Tb

Dy

HoErYb

Lu

Hf

OsIrTl

Pb

U

1:1

high in meteorites,destroyed in sun

abundant in sun,volatile compoundslost from meteorites

Comparison of solar and CI chondritic abundances (both scales normalized to Si=106):

Good correlation for many heavy elements (1:1 line)

Meteorites depleted in elements that form volatile compounds Noble gases, CO, CH4, N2, H2O

Photosphere depleted in Li

Abundances of “missing” rock-forming elements in photosphere can be derived from CI-chondrites

Photospheric abundances are not equal to protosolar abundances

He and heavy elements settled from the solar photosphere over Sun’s lifetime

Protosolar PhotosphericA(He) 10.984 10.899 drop by ~18%

Heavy elements relative to H drop by ~16%

A(El) protosolar = A(El) photospheric + 0.074

Add 0.074 dex to the photospheric abundance to get protosolar (solar system) abundances for heavy elements

On the cosmochemical scale relative to Si=106, only the H and He abundances change

atomic number, Z0 10 20 30 40 50 60 70 80 90

sola

r sy

stem

abu

ndan

ce b

y nu

mbe

r, S

i = 1

06 a

tom

s

10-2

10-1

100

101

102

103

104

105

106

107

108

109

1010

1011

H

He.

Li

Be

B

C

N

O

F

Ne

Na

Mg

Al

Si

P

S

Cl

Ar

K

Ca

Sc

Ti

V

CrMn

Fe

Co

Ni

CuZn

Ga

Ge

As

Se

Br

Kr

Rb

Sr

YZr

Nb

MoRu

Rh

Pd

Ag

Cd

In

Sn

Sb

Te

I

Xe

Cs

Ba

La

Ce

Pr

Nd

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

Hf

Ta

WRe

OsIrPt

AuHg

Tl

Pb

Bi

Th

U

mainly neutron capture on rapid and slow time scales

(R and S process)

nucle

ar s

tatis

tical

equ

ilibriu

m

oxyg

en b

urni

ng

heliu

m b

urni

ngsil

icon

burn

ing

H bur

ning

carb

on b

urni

ng

BB

BBX

Elemental abundances vs. atomic number

Solar abundances of the elements are controlled by nuclear properties, not chemical (electron shell) properties

odd-numbered

elements only

atomic number, Z0 10 20 30 40 50 60 70 80 90

sola

r sy

stem

abu

ndan

ce b

y n

umbe

r, S

i = 1

06 a

tom

s

10-210-110010110210310410510610710810910101011

H

LiB

N

F

NaAl

P Cl K

Sc

V

MnCo

Cu

GaAsBrRb Y

Nb RhAgInSb

ICsLa

Pr EuTbHoTmLuTa

Re

IrAuTl Bi

even-numbered

elements only

10-210-110010110210310410510610710810910101011

He.

Be

C ONeMgSi S

ArCa

TiCr

Fe

Ni

Zn

GeSeKrSr Zr

MoRuPdCdSnTeXeBa

LaNdSmGdDyErYbHf W

OsPtHg

Pb

ThU

Separate for even and odd-numbered elementsElemental abundances as function of atomic number (= proton number=Z) show “peaks” e.g., O (N), Fe (Ni), Ba (I), Os (Ir)

Do not follow electron shell stabilities(noble gases are not the most abundant heavy elements)

280 naturally occurring stable (266) and long-lived nuclides (14)

Nuclides belonging to the same element (same proton number Z) are isotopes“isos + topos” = in the same place in the periodic table

Fe

Sn-Ba

I-Cs

Os-Pt

Mn

Ir

Look at nuclide distributions to decipher what controls elemental abundances

mass number, A

0 20 40 60 80 100 120 140 160 180 200 220 240

abun

danc

e, S

i=10

6 a

tom

s

10-3

10-2

10-1

100

101

102

103

104

105

106

107

108

109

1010

1011

odd mass numbers

80 100 120 140 160 180 20010-2

10-1

100

101

1H

16O12C20Ne 56Fe

9B89Y

138Ba

40Ca

117,119Sn

164Dy

195Pt

208Pb

195Pt

89Y

117,119Sn

137Ba139La

169Tm

169Tm

Abundances peak at mass numbers for closed proton and neutron shells

“magic numbers”2, 8, 20, 28, 50, 82, 126

Doubly-magic nuclei; e.g.4He Z = N = 216O Z = N = 840Ca Z = N = 20

Abundances of the nuclides versus mass numbers

266 stable nucleiZ even, N even: 159 nuclidesZ even, N odd: 53 nuclidesZ odd, N even: 50 nuclidesZ odd, N odd: 4 nuclides (2H, 6Li, 10B, 14N)

Lower number of odd-Z numbered isotopes lower abundances of odd-Z numbered elements

S, R, P –process contributions to the elemental abundances

Example Zr:5 isotopes, relative contribution of each isotope to total element is known (usually a terrestrial std)

Abundance of each isotope rel. Si=106 atoms

For each isotope: amount from main S-process from low & intermediate AGB stars from nucleosynthetic network calculations; Arlandini et al. 1999, Winckler 2006

Amount from weak S-process (Raiteri et al. 1992, Travaglio et al. 2004)

R process contribution by difference to isotope abundance (“R residuals”), Or R process network calculations (Kaeppeler, Karlsruhe group)

Sum of R and S abundances of each isotope gives contributions of S and R process to elemental abundance of Zr: main S = 65%, weak S = 2%, R = 33%

Legend:

atomic number, Z40 50 60 70 80 90

fra

ctio

n o

f to

tal e

lem

en

t

0.0

0.2

0.4

0.6

0.8

1.0As SeBr Kr Rb Sr Y Zr NbMoTc RuRhPdAgCd In SnSb Te I XeCsBa La Ce Pr NdPmSmEuGdTb DyHo ErTmYb Lu Hf Ta W ReOs Ir Pt AuHg Tl Pb Bi Th U

weak S R processP processmain S

Main S process: evolved low & intermediate mass (AGB) stars

Weak S and P and R processes: massive stars

Contributions of different nucleosynthesis processes to the abundance of each elementPbBa

The solar system abundances of the elements are reasonably well known,but large uncertainties remain for several elements

Re-analyses for several elements are needed

Are differences between solar photosphere and CI-chondrite data real or the result of analytical difficulties?

Photosphere: e.g., Sc, Ti, Mn, Ca, Ga, Ge, Sn, Rb, Ag, In, Au, W, Tm, Lu, Th, U, Hg

Sun-spot data: F, Cl, Tl

But also in CI-chondrites: e.g., Be, Hg

Isotopic compositions of the elements are mainly taken from terrestrial rocks and meteorites – are these the same in the Sun?