Transcript Slide 1

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 system
Composition of the solar system, planetary compositions
Origin of the elements
Abundance 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 formation
ISM/ molecular cloud composition 4.6 Ga ago
proto-solar abundances
Li, D, short-lived radioactive nuclides (26Al, 129I),
long-lived (=still present) radioactive nuclides (87Rb, 235U, 238U, 232Th)
Cosmic abundances: this term should be avoided
many 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 = percent
g 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 air
20.95% 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 quantity
Abundance Scales and Notations
Most commonly used: Atoms by number, N
Normalized to a reference element
Astronomical abundance scale:
normalized to H, the most-abundant element in universe
eH = 1012 atoms
converted to log scale: A(H) = log eH = 12
abundances are measured relative to H, e.g.,
N(Fe)/N(H)
log eFe = 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 crust
Meteorites
Other solar system objects, gas-giant planets, comets, meteors
Solar photospheric spectrum, SW, SEP
Spectra of other dwarf stars (B stars)
Interstellar medium
H II regions
Planetary 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
What controls the abundances of the elements?
Abundances of the elements
50
as a function of atomic number
Earth crust, igneous rocks
Clarke 1898, Harkins 1917
no discernable trends of
abundance with atomic
number or atomic weight
 Abundances are modified
from solar during Earth’s
formation and differentiation
Abundances in igneous rocks
40
Weight Percent
Quantitative analyses limited
to abundant elements in rocks
O
(Table IX, col. II of Harkins 1917)
30
Si
20
10
Al
Na
0
C
6
F
K
Mg
P S Cl
Fe
Ca
Ti
Cr
Ni
8 10 12 14 16 18 20 22 24 26 28
Atomic Numbers
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 crust
elements follow geochemical character
siderophile 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 crust
Mg, 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)
red
giants
super
novae
dust
Molecular cloud composition
4.6 billion years ago
= solar system composition
presolar molecular cloud
evaporation &
recondensation
of dust
proto-Sun &
solar nebula
gas giant protoplanets
begin to form
recondensed
silicate
metal
sulfide
preserved
presolar
dust
agglomeration
accretion,
planetesimal
growth
primitive planetesimals
chondrite parent bodies
differentiated
planetesimals
break-up
terrestrial
planets
large
impacts
metallic core
formation during
heating
irons
achondrites
crust formation
basaltic volcanism
Earth crust today
Sign Convention:
Elements
detected
in celestial
bodies
Extend search for chemical
elements to other celestial objects
(Kleiber 1885; 68 elements out of 83
are known)
Earth’s crust
meteorites
Comets
Meteors
Sun
Other stars
Composition of celestial objects is
not random
Elements
not detected
in celestial
bodies
-
Zi
Be
B
C
N
O
F
Na
Mg
Al
Si
P
S
Cl
K
Ca
Sc ?
Ti
V
Cn
Mn
(Cu)
Zn
Ga ?
As
Se
Br
Rb
Sr
Yt
Zr
Nb ? Mo
(Ag)
Cd
In
Sn
Sb
Cs
Ba
La
Ce
Di -
(Au) - Hg
Tl -
Ta ?
Pb
Th -
Te
W-
Bi
U
Presence of
elements
is uncertain
I.A. Kleiber's table
on the chemical
composition
of celestial bodies
1885
H
Er -
Helium found in 1868 but not plotted by
Kleiber, no other noble gases known at
the time
Presence of
elements is
very uncertain
?
Fe
Co
Ru ? Rh ?
Ni
Cu
Pt
Ag
I-
Os -
Ir -
Pt -
Au -
40
Abundances vs. atomic number 1917:
O
Harkins 1917
ABUNDANCE OF THE ELEMENTS
(stony meteorites; Harkins 1917)
30
Use average abundances from
meteorites,
no photospheric abundances yet
Weight Percent
Even-numbered elements are more
abundant than their odd-numbered
neighbors
Fe
20
Si
Mg
Li, B, Be low in abundances
C low because of volatility, but still
more abundant than odd numbered
neighbors B or N
10
Fe peak
Abundances of elements heavier than
Fe (Z > 26) are quite low
S
0
C
6
Na
Al P
Ca
K
Ni
Ti
Cr
Co
8 10 12 14 16 18 20 22 24 26 28
Atomic Numbers
Harkins’ discovery graph of the odd-even
effect in elemental abundances
Rare Earth Minerals
Goldschmidt & Thomassen, 1924
Odd-Even distribution of the elements
as a function of atomic number is also
seen for heavy elements
30
20
10
80
Sun's Atmosphere Russell 1929
as of 2007
60
Good example: rare earth elements
(REE)
Similar geochemical behavior
40
20
80
Shales (sedimentary rocks)
Minami, June 1935
Odd-even abundance effect not
(completely) erased during redistribution of REE among minerals in
rocks
60
40
20
30
Meteoritic Stones I. Noddack, Nov. 1935
CI-chondrites as of 2003
20
10
Figure updated from Goldschmidt 1937
Normalized to Y= 100 atoms (Y not shown)
0
Ce
La
Russell
Nd
Pr
Sm
Pm
Gd
Eu
Dy
Tb
Er
Ho
Yb
Tm
Lu
Meteorites
Chondrites: most common types of meteorites
Mixtures of silicates, metal and sulfides that may have been
processed subsequently on their parent asteroids
recondensed
silicate
metal
sulfide
agglomeration
preserved
presolar
dust
accretion,
planetesimal
growth
primitive planetesimals
chondrite parent bodies
Achondrites and iron meteorites: experienced melting and/or
extensive re-crystallization on their parent asteroids
differentiated
planetesimals
break-up
terrestrial
planets
large
impacts
metallic core
formation during
heating
irons
achondrites
crust formation
basaltic volcanism
Photo Christian Anger 2006
Kodaikanal meteorite
Found 1898, 15.9 kg, IIE iron, fine octahedrite with silicate inclusions
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
Photo: Le Muséum National d'Histoire Naturelle, Paris
Orgueil meteorite
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)
CV chondrite:
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:
concentration ratio CM chon./CI chon.
2.0
W
volatility trend in
CM chondrites
Zr
Hf
1.5
Nb
Pr
Os
Re
Be
Ce
Gd Tm U
Eu
Ca
Sc
Mo
Th
Ba
V
Al
Ta
Yb
Mg Si
Y
Ir Ru Sr
Rh Fe
Ni Cr
Ti
Pt
Co
1.0
Pd
As
P
Li
Mn
0.5
Au
Cu
Sb
Ag
Na
K
lithophile
siderophile
chalcophile
halogen
Ga Cl
Se
Zn
F
Ge
Rb
B
Cs
Bi
Pb
Br
Tl
I
Cd
Te
Sn
S
In
0.0
1800
1600
1400
1200
1000
800
600
50% condensation temperature, K, at 10-4 bar
Independent of geochemical character
400
concentration ratio CV chon./CI chon.
Zr
Be
Gd
La Ca
Hf Al U Ti
Ba
Lu
Yb
Th
PrNb
Sr
2.0
W
volatility trend in
CV chondrites
Eu
Ce
Sc
Y
Mo
Ru
V
Os
1.5
Mg
Ir
Re
Si
CoFe Cr
Pt Ni
Pd
Rh
P
Li
Au
1.0
Mn
0.5
As
Cu
K Na
Ga
Sb
Ag
lithophile
siderophile
chalcophile
halogen
Te Se
Ge
B
Rb
Cs Bi
Pb
Br
Cd
S
Tl
Cl
F
Sn
In
Zn
I
0.0
1800
1600
1400
1200
1000
800
600
50% condensation temperature, K, at 10-4 bar
Independent of geochemical character
400
concentration ratio H chon./CI chon.
1
Re
OsW
Zr
Sc Ir Mo
Ru
Y
U
Hf Al
Ti Ca
Yb
Co
Ni
Rh
Ba
Pt
V
REE Nb Ce Be
Sr
Ta
Th
Si
EuMg Cr
P
Au
As
Mn
K
Na
Rb
Mg Fe
Pd
Li
Cu
Ga
B
Sb
F Se
Ge
Cs
S
Sn
0.1
Ag
volatility trend in
H chondrites
Br
Te
Zn
Cl
I
Bi
Pb
F
Cd
Tl
0.01
lithophile
siderophile
chalcophile
halogen
1800
1600
In
1400
1200
1000
800
600
50% condensation temperature, K, at 10-4 bar
Independent of geochemical character
400
Abundances in the photosphere, CI chondrites, meteors, and cometary samples
Halley dust
CI chon
photosp.
Taurid
Geminid
Perseid
CometWild2
Wild2 resi
1e+7
1e+6
1e+5
abundance (atoms/100 Fe)
1e+4
1e+3
1e+2
1e+1
1e+0
1e-1
1e-2
1e-3
1e-4
1e-5
1e-6
1e-7
H He Li Be B C N O F NeNaMgAl Si P S Cl Ar K CaSc Ti V CrMnFeCoNiCuZnGaGeAsSe
Comet Halley data: Schultze et al, Jessberger et al; Comet Wild 2 data from Flynn et al. 2006
Sun holds more than 99% of
the solar system’s mass
100
10
Composition of Sun should
be good approximation for
solar system as a whole
mass distribution in the
solar system
1
0.1
0.001
Sun
mass%
0.01
Eris
Pluto
Neptune
Saturn
Earth
Mars
Ceres
0.00000001
Venus
0.0000001
Mercury
0.000001
Jupiter
0.00001
Uranus
0.0001
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 transitions
Fe several thousand lines, other elements only 1 line accessible
Line blending
Ni and Fe lines interfere; e.g., determinations of O, Th
Transition probabilities and lifetimes of atomic states
recent re-analysis of transition metals and REE
Atmospheric models
continuum modeling (e.g., UV for Be)
LTE vs. non LTE, is radiation in local equilibrium with matter
2D, 3D
granulation, convection
He abundance
Determined 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 abundance
to increase opacity in sun’s interior (Bahcall)
But solar Ne abundance is also derived
indirectly, e.g., from Ne/O ratio in SW
Lower O  also lower Ne
“Solar” Ne abundance needs to be worked out
Solar Ar abundance
Comparison of solar and CI chondritic abundances
(both scales normalized to Si=106):
1011
H
Good correlation for many
heavy elements (1:1 line)
Photosphere depleted in Li
Abundances of “missing”
rock-forming elements in
photosphere can be derived
from CI-chondrites
He.
109
108
abundant in sun,
volatile compounds
lost from meteorites
107
6
solar photosphere; Si = 10 atoms
Meteorites depleted in
elements that form
volatile compounds
Noble gases, CO,
CH4, N2, H2O
1010
Ne
106
N
S
105
Ar
Cr
ClMn
P
TiK
Co
FZn
Cu
V
103
101
Ge
Kr
Sc
Sr
Ga
RbZrB
Y
Ba
Pb
Sn
Mo
Ru
Cd
Pd
Ce
Os
Nd
Nb
Be
Ir
Dy
La
Rh
Gd
Li
Yb
Sm
Sb
Tl
Er
Hf
Pr
Eu
Ho
Tb
Lu
Xe
100
10-1
10-2
Mg
Si
Fe
Al
Ca
Na
Ni
104
102
O
C
1
1:
high in meteorites,
destroyed in sun
U
10-3
10-5 10-4 10-3 10-2 10-1 100 101 102 103 104 105 106 107 108
CI-chondrites; Si = 106 atoms
Photospheric abundances are not equal to protosolar abundances
He and heavy elements settled from the solar photosphere over Sun’s
lifetime
Protosolar
A(He) 10.984
Photospheric
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
rn
O
Ne
Mg Si
Fe
Na
104
Ar
Al
P
103
Cl
Ca
K
Ti
Sc
Ga
Se Kr
Sr
As
Br
Rb
Zr
Y
Mo Ru
Nb
Be
Sn Te
Pd Cd
Rh Ag
In
BB
X
10-1
m
Zn
Cu
B
100
riu
Co
Ge
101
ilib
Cr
Mn
V
Li
mainly neutron capture
on rapid and slow time scales
(R and S process)
Ni
F
102
qu
nu
S
105
ar
N
106
st
C
cle
107
le
108
ica
H
He.
109
at
ist
bu
H
1010
in
BB
he
ca lium
ox rbo bu
yg n b rn
en ur ing
sil
bu nin
ico
rn g
n
in
bu
g
rn
in
g
6
solar system abundance by number, Si = 10 atoms
1011
g
Elemental abundances vs. atomic number
10-2
Xe Ba
I
Sb
Pb
Pt
Ce Nd
OsIr
Hg
Dy
Cs La
SmGd
Er Yb
Au Tl Bi
Pr
Hf W
Eu
Ho
Tb
Re
Tm Lu
Ta
Th
U
0
10
20
30
40
50
atomic number, Z
60
70
80
90
Solar abundances of the elements are controlled by nuclear properties, not
chemical (electron shell) properties
Do not follow electron
shell stabilities
(noble gases are not the most
abundant heavy elements)
280 naturally occurring
stable (266) and longlived nuclides (14)
Nuclides belonging to the
same element (same
proton number Z) are
isotopes
“isos + topos” = in the same
place in the periodic table
Separate for even and odd-numbered elements
solar system abundance by number, Si = 106 atoms
Elemental abundances
as function of atomic
number (= proton
number=Z) show “peaks”
e.g., O (N), Fe (Ni), Ba
(I), Os (Ir)
1011
1010
109
108
107
106
105
104
103
102
101
100
10-1
10-2
1011
1010
109
108
107
106
105
104
103
102
101
100
10-1
10-2
He.
Fe
C O
NeMgSi
Fe
S
ArCa
Cr
Ti
even-numbered
Ni
elements only
Sn-Ba
Zn
GeSe
Kr
Be
Sr
Os-Pt
Zr
Pb
MoRuPdCdSnTeXeBa
LaNd
Os Pt Hg
Dy
Gd
Sm
ErYb Hf W
Th
H
Mn
N
odd-numbered
elements only
Na Al
Mn
Co
Cu
V
P Cl
K
F
Li
Sc
B
I-Cs
Ga
As BrRb Y
Nb
0
10
20
30
I
RhAg In Sb CsLa
40
50
atomic number, Z
Pr
Ir
Ir
EuTbHo
TmLu
60
Look at nuclide distributions to decipher
what controls elemental abundances
70
Re
Ta
Au Tl Bi
80
90
U
Abundances of the nuclides versus mass numbers
1011
Abundances peak at mass
numbers for closed proton
and neutron shells
Doubly-magic nuclei; e.g.
4He
Z=N=2
Z=N=8
40Ca Z = N = 20
16O
H
1010
101
89
odd mass numbers
Y
109
108
abundance, Si=106 atoms
“magic numbers”
2, 8, 20, 28, 50, 82, 126
1
16
12
C
O
20
107
106
Ne
56
40
105
Fe
Ba
139
La
10-1
117,119
169
10-2
80
100
Pt
Sn
Ca
104
195
137
100
120
140
Tm
160
180
200
103
102
138
101
208
195
100
164
9
10-1
Ba
B
89
Y
Pb
Pt
Dy
117,119
Sn
10-2
266 stable nuclei
Tm
-3
Z even, N even: 159 nuclides
10
0
20 40 60 80 100 120 140 160 180
Z even, N odd: 53 nuclides
mass number, A
Z odd, N even: 50 nuclides
Z odd, N odd: 4 nuclides (2H, 6Li, 10B, 14N)
Lower number of odd-Z numbered isotopes
lower abundances of odd-Z numbered elements
169
200 220 240
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%
Contributions of different nucleosynthesis processes to the abundance of each element
Pb
Ba
1.0
As SeBr Kr Rb Sr Y Zr NbMoTc RuRhPd AgCd In Sn Sb Te I Xe Cs Ba La Ce Pr NdPmSmEuGdTb DyHo Er TmYb Lu Hf Ta W ReOs Ir Pt AuHg Tl Pb Bi
Th
fraction of total element
0.8
0.6
0.4
0.2
0.0
40
Legend:
50
main S
Main S process: evolved low & intermediate
mass (AGB) stars
60
70
atomic number, Z
weak S
80
P process R process
Weak S and P and R processes: massive stars
90
U
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?