Neutrons for Cosmochemistry Identification of Impacting ... · Neutrons for Cosmochemistry Identification of Impacting Asteroids Gerhard Schmidt Institute of Earth Sciences Heidelberg

Neutrons for Cosmochemistry

Identification of Impacting Asteroids

Gerhard Schmidt

Institute of Earth Sciences

Heidelberg University

Modified from Matthäus Merian

Comet over Heidelberg

Copperplate

Beginning of the 17th century

16th Rußbach School on Nuclear Astrophysics, March 2019

Heidelberg at the beginning of the 22th century?

Introduction - Neutron Activation Analysis

https://www.youtube.com/watch?v=KiOzQ-K0gEQ

Movie by Lea Canella from FRM II, Technical University Munich (TUM)


Characteristic blue glow of an under water nuclear reactor due to Cherenkov radiation

Thermal Neutron Activation Analysis (NAA)

with low power research reactors

• TRIGA (Training Research Isotopes General Atomics) reactors were constructed in San Diego (California) in the 1950s • TRIGA reactors are inherently safe - meltdown impossible ! • NAA most important tool for chemical analyses of small samples • samples are exposed to thermal neutrons and neutron-rich nuclei are produced by neutron capture • some nuclei are radioactive and decay with various half lives whereby they release γ-rays with characteristic energies • radioactivity of an element is proportional to the number of nuclei of a specific isotope present in the sample

• large volume semi-conducting detectors (Li-drifted Ge crystals) for γ counting high energy resolution and high efficiency


Different procedures

a. INAA: Instrumental NAA, powder samples irradiated directly, without chemical treatment

b. RNAA: Radiochemical NAA, samples chemically treated after irradiation

Advantage: many elements can be 2-3 orders of magnitude more sensitive detected, considerably more elements can be analysed Disadvantage: time-consuming procedure, special laboratory equipment for handling of radioactive materials required

c. DNAA: Delayed Neutron Activation Analysis is based on the fission of nuclei induced by neutron

capture, and subsequent detection of fission products according to decay of emitted neutrons, number of neutrons emitted is proportional to content of fissile nuclides in sample e.g. for 235U, 232Th, 233Pu, 239Pu, 240Pu (used as relative method) - neutron counter required

d. Extraction and enrichment: Groups of elements extracted and enriched before NAA

Advantage: elements are extracted from larger quantities (homogeneity), thus 2-3 orders of magnitude better detection limits, more elements can be analyzed, low activity, as only small amounts of nuclides with high activity (24Na, 60Co, 59Fe, 46Sc, 51Cr) are produced Disadvantage: very clean work in laboratory, ng quantities must be extracted and enriched, yield determination required

e. PGAA (promt gamma neutron activation analysis) → H, Li, Be, B, C, N, P, S, V, Mn, Cd, Sm, Nd, Gd, Tl, Pb…


Principle of NAA

Ax = cx = concentration sample

cSt = concentration standard

induced radioactivity of the element to be analyzed in the sample

At = activity generated after irradiation time (s-1) m = mass of target material (g) λ = decay constant of produced nuclide σ = cross section in (cm2) φ = particle flux density (cm2 x s1 x n) M = atom mass of nuclide NL = Loschmidt number H = isotope abundance of target nuclide t = irradiation time t‘ = decay time

production decay

Crocket J. H. & Cabri L. J. (1981)


Overview of transformations of nuclides by nuclear reactions

protons

number of nucleons

neutrons


58Ni (n,p) 58Co

13C (α,n) 16O

Slow neutron captures are

responsible for the production

of about 50% of elements

heavier than iron, where the

main neutron source is the 13C (α,n)16O reaction.

(e.g. Trippella et al. 2016)

Trippella, M. Busso, S. Palmerini, E. Maiorca & M. C. Nucci (2016) s-processing in AGB stars revisited.

II. Enhanced 13C production through MHD-induced mixing. The Astrophysical Journal, 818:125 (9pp)

Part of the Chart of Nuclides showing the nuclides measured


99Tc (n,γ) (T1/2 = 211000 a) 100Tc (T1/2 = 15.8 s) β-

100Ru (stable)

Sensitivity of some elements for neutron activation analysis

Commas in table represent points

PF = production factor λ = decay constant σ = cross section in (cm2) a = isotope abundance of target nuclide t1 = irradiation time t2 = decay time W = isotopic mass

PFt1 = 12 hrs PFt2 = 19 hrs

Crocket J. H. & Cabri L. J. (1981) Analytical methods for the platinum-group-elements. In: Platinum-Group-Elements: Mineralogy, Geology and Recovery. Cabri L.J. (ed ) Canadian Inst Mining Metall Pet Spec Vol 23, p 71-79 Crocket J. H., Keays R. R. & Hsieh S. (1968) Determination of some precious metals by neutron activation analysis. J. Radioanal. Chem. Vol. 1, 487-507


(1) number of target nuclei of an element – proportional to the concentration (2) neutron capture cross section of the target nucleus (3) half life and decay scheme of the radioactive, neutron-rich nuclei produced by neutron irradiation

Examples: rare element Ir is very sensitive to NAA, abundant element Si cannot be determined by NAA Analysis of Rh, Mg and Al, with short-lived radionuclides requires neutron irradiation of a short duration

Example of a Gamma-Spectrum from a Particle Returned from

Asteroid Itokawa

Gamma-ray spectrum for the irradiated sample (49-1) with 40 days for cooling interval. The inset in (B) was expanded for the energy region of 310 to 330 keV

from same spectra. Figure from Ebihara et al. (2011) Supporting Online Material, Science 333.

Figure from M. Ebihara, S. Sekimoto, N. Shirai, Y. Hamajima, M. Yamamoto, K. Kumagai, Y. Oura, T. R. Ireland, F. Kitajima, K. Nagao, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, A. Tsuchiyama, M. Uesugi, H. Yurimoto, M. E. Zolensky, M. Abe, A. Fujimura, T. Mukai & Y. Yada (2011) Neutron Activation Analysis of a Particle Returned from Asteroid Itokawa, Science 333, 1119-1120


Extraction and enrichment of PGE, Re and Au

(1) elements extracted and enriched before NAA from homogenized sample powders! Advantage: elements are extracted from larger quantities (homogeneity, nugget effect)... Disadvantage: very clean work in laboratory! (2) nickel sulfide fire assay collection two irradiations: (3) irradiation time 5 min at a thermal neutron flux of 1.7 × 1012 neutrons cm-2 sec-1

in a hydraulic rabbit facility 2 min decay time, 8 min counting time 104mRh (T1/2 = 4.41 min) γ-peak at 51 keV (4) irradiation time 12 hrs at a flux of 4 × 1012 neutrons cm-2 sec-1

16 hrs decay time 109Pd, 188Re, 199Au (for Pt), 198Au, 192Ir, 191Os, 103Ru Advantage: high photopeak to Compton background ratio (5) samples and standards measured several times (special counting strategies!)


Locations of impact craters

https://www.lpi.usra.edu

Steinheim (3.8 km) and Ries

impact crater (25.5 km)

• impact craters situated on the Upper Jurassic limestone plateau of the Suebian and Franconian Alb

(SW Germany)

• unbalanced distribution of Suevite and its frequency in the south is a consequence of the erosion

of the soft ejekta in the northern part of the crater

Nördlinger Ries and Steinheim impact craters

both structures - middle Miocene age, 14.8 Ma Ackerman et al. 2017

No detectable meteoritic contaminations of Iridium in the bore-hole Nördlingen 1973 Schmidt and Pernicka 1994, Ackerman et al. 2017

Nördlingen

• Nördlinger Ries → impact crater (Shoemaker & Chao 1961)

• 14.8 Ma

• 24 - 26 km diameter crater

• excavated from carbonate-bearing sedimentary sequences and underlying

crystalline silicate basement materials

bore-hole

FBN73

Clearwater East impact structure (Canada)

Comparing the elemental ratios in the impactites of the Clearwater East structure with those calculated from the database of Tagle

and Berlin (2008) for chondrite groups. Error values of 5% of the ratios are indicated for chondrites. Figure modified after

McDonald (2002) Meteoritics and Planetary Science 37. Clearwater East data from Schmidt (1997) Meteoritics and Planetary

Science 32. 10 g aliquot of sample powder used for PGE analysis of Clearwater melts.

PGE ratios and Cr isotopes → ordinary chondrite McDonald 2002; Schmidt 1997; Shukolyukov and Lugmair 2000

→ bolide typ L chondrite (~ 7% of a nominal CI component)

Ordovician East Clearwater, ~ 26 km diameter, ~460 – 470 Ma (Schmieder et al. 2015)

• impact of small asteroid from the breakup of the 100 – 150 km diameter L-chondrite parent body in

the asteroid belt (Schmitz et al. 2003, 2018)

Permian West Clearwater impact (⩾36 km)

286.2 ± 2.2 Ma (Schmieder et al. 2015)

16th Rußbach School on Nuclear Astrophysics, March 2019 Commas in axis labels represent points.

Case studies for the identification of iron projectiles (Sääksjärvi) and chondrites

(Clearwater East) from terrestrial impact craters

bolide types

Sääksjärvi → iron meteorite Schmidt, Palme, K.-L. Kratz (1997)

~ 0.4% of a nominal magmatic iron meteorite component

Geochimica et Cosmochimica Acta

Clearwater East → chondrite Schmidt (1997)

~ 4 to 7% of a nominal CI meteorite component

Meteoritics and Planetary Science

Comparing the elemental ratios in the impactites of the Sääksjärvi and Clearwater East structures with those calculated from the database of Tagle and Berlin (2008) for

chondrite groups. Error values of 5% of the ratios are indicated for chondrites. Sääksjärvi melt data from Schmidt, Palme, K.-L. Kratz (1997) Geochimica Cosmochimica

Acta 61. Clearwater East data from Schmidt (1997) Meteoritics and Planetary Science 32. Mantle data from Becker, Horan, Walker, Gao, Lorand & Rudnick (2006)

Geochimica et Cosmochimica Acta 70 and Fischer-Gödde, Becker & Wombacher (2011) Chemical Geology 280.

10 g aliquot of sample powder used for PGE analysis of melt samples.


Commas in axis labels represent points.

Ru/Rh vs Ir/Rh mass ratios from Clearwater East melt samples

and acapulcoite meteorites

Comparing the elemental ratios in the impactites of the Clearwater East structure with those calculated from the database of Tagle and Berlin (2008) for different types of chondrites. Error values of 5% of the ratios are indicated for chondrites. Acapulcoite and Lodranite data from Dhaliwal et al. (2017) Early metal-silicate differentiation during planetesimal formation revealed by acapulcoite and lodranite meteorites. Geochimica et Cosmochimica Acta 216, 115-140. Indicated mantle ratios of Ir/Rh = 2.94 ± 0.47 (n=65) and Ru/Rh = 6.0 ± 0.7 (n=61) from Fischer-Gödde, Becker & Wombacher (2011) Chemical Geology 280. Ru, Ir and Rh data for Clearwater East melt samples from Schmidt (1997) Meteoritics and Planetary Science 32. 10 g aliquot of sample powder used for PGE analysis of Clearwater melts. Ratios for mantle rocks (n=13) from Schmidt (2004); Ir/Rh = 2.41 ± 0.49; Ru/Rh = 4.84 ± 0.98 (not indicated).

Ru/Rh vs Ir/Rh → ordinary chondrite McDonald 2002; Schmidt 1997; Shukolyukov and Lugmair 2000

Ru/Rh and Ir/Rh element ratios in FeNi grains from acapulcoite meteorites match those from Clearwater East melt samples



Ru/Rh vs Ir/Rh mass ratios from Clearwater East, Sääksjärvi, Boltysh, Mien,

Dellen impact melt samples, acapulcoites, chondrites and the Earth's mantle

Comparing the elemental ratios in melts from impact craters with those calculated from the database of Tagle and Berlin (2008) for different groups of chondrites. Error values of 5% of the ratios are indicated for chondrites. Acapulcoite and Lodranite data from Dhaliwal et al. (2017) Geochimica et Cosmochimica Acta 216, 115-140. Mantle ratios; Ir/Rh = 2.94 ± 0.47 (n = 65); Ru/Rh = 6.0 ± 0.7 (n = 61) from Fischer-Gödde, Becker & Wombacher (2011) Chemical Geology 280. Ru, Ir and Rh data for Clearwater East and Boltysh melt samples from Schmidt (1997) Meteoritics and Planetary Science 32. Data for Sääksjärvi, Mien and Dellen melt samples from Schmidt, Palme & Kratz (1997) Geochimica et Cosmochimica Acta 61, 2977 - 2987. 10 g aliquot of sample powder used for PGE analysis of melt samples. Ratios for mantle rocks (n=13) from Schmidt (2004); Ir/Rh = 2.41 ± 0.49; Ru/Rh = 4.84 ± 0.98 (not indicated).

Ru/Rh vs Ir/Rh → ordinary chondrite McDonald 2002; Schmidt 1997; Shukolyukov and Lugmair 2000

Ru/Rh and Ir/Rh element ratios in FeNi grains from acapulcoite meteorites match those from Clearwater East melt samples



Ru/Rh vs Ir/Rh mass ratios from impact melt samples and chondrite groups

Comparing the elemental ratios in the impact melts with different groups of chondrites, calculated from the database of Tagle and Berlin (2008, Meteoritics & Planetary Science 43, 541–559). Error values of 5% of the ratios are indicated for chondrites. Mean CI ratios from Palme, Lodders & Jones (2014) Treatise on Geochemistry. Impact melts Schmidt (1997) Meteoritics and Planetary Science 32, 761-767 Schmidt, Palme & Kratz (1997) Geochimica et Cosmochimica Acta 61, 2977 - 2987 Tagle and Claeys (2005) Geochimica et Cosmochimica Acta 69, 2877-2889 McDonald, Andreoli, Hart & Tredoux (2001) Geochimica et Cosmochimica Acta 65, 299–309 Tagle, Schmitt & Erzinger (2009) Geochimica et Cosmochimica Acta 73 , 4891-4906 Goderis, Kalleson, Tagle, Dypvik, Schmitt, Erzinger & Claeys (2009) Chemical Geology 258, 145-156



Ru/Rh vs Ir/Rh from impact craters, tektites, iron meteorites, chondrite groups

and the Cretaceous-Paleogene boundary


Data for magmatic irons from Cook et al. (2004), Petaev and Jacobsen (2004) and Walker et al. (2008) compiled by Day et al. (2016).

Formation of the Earth ~4.57 billion years ago

Figure from D. L. Anderson (1990) in „The New Solar System“ Cambridge University Press

1. in a first step the dust in the solar nebula

was transformed into the proto-planet

Earth

2. impacts dominate earliest history of

Earth formation

3. in a next step nickel-iron separated from

silicates and stripped the proto-Earth’s

mantle of all the highly siderophile

elements (Os, Ir, Ru, Rh, Pt, Pd, Re, Au)

→ core formation was finished

~ 30 Ma after Earth formation

(e.g., Kleine T. et al. 2002 Rapid accretion and early

core formation on asteroids and terrestrial planets

from Hf‐W chronometry. Nature 418, 952–955)


Late Veneer Hypothesis

Figure from P. D. Spudis (1990) in „The New Solar System“ Cambridge University Press

4. Collision with a Mars-sized object - late-accreted mass ≤ 1 % of Earth’s mass - HSE clock limits the timing of the Moon-forming event to significantly later than 40 Myr after condensation (Jacobsen et al. 2014, Nature 508)

→ Re, Os, Ir, Ru, Pt, Rh, Pd and Au added to accreting Earth after core formation

3.9 Ga signature EH or LL chondrite Ru/Ir = 1.8 Norman et al. 2002

Apollo 17 Ru/Ir = <1.7

Earth Ru/Ir = 2


Figure from Schmidt (2009) Workshop on Planet

Formation and Evolution: The Solar System and

Extra Solar Planets, Tübingen

Correlation of solar system normalized abundances of PGE in the Earth's mantle

with condensation temperature in a gas of solar composition


Mantle abundances from Schmidt (2004). Meteoritics and Planetary

Science 39, 1995-2007. Mean CI abundances from Palme, Lodders &

Jones (2014) In: Holland H.D., Turekian K.K. (Eds.) Treatise on

Geochemistry, Volume 2. Second edition. Elsevier, Oxford,15–36.

Condensation temperature from Lodders (2003)

The Astrophysical Journal 591: 1220–1247.

Error bars are population standard deviations (σ).Commas in axis label represent points.

Abundances of elements in mantle samples from

aliquots of ~ 10 to 20 g homogenized sample

powder < 50 µm measured by neutron activation

and normalized to mean CI chondrites are plotted

against their 50% condensation temperature.

There is a continuous decrease of abundances

with decreasing volatility as measured by the

condensation temperature.

Excesses in Pd, Ru, and Rh in the terrestrial pattern


Mean chondrite abundance data compiled from Tagle & Berlin (2008) Meteoritics & Planetary Science 43.

Mean CI abundances from Palme, Lodders & Jones (2014) Treatise on Geochemistry. Os, Ir, Ru, Pt, Pd

from Becker, Horan, Walker, Gao, Lorand & Rudnick (2006) Geochimica et Cosmochimica Acta 70 and

Rh from Fischer-Gödde, Becker & Wombacher (2011) Chemical Geology 280 assuming primitive mantle

Al2O3 of 4.25 ± 0.25 wt.%.

Commas in axis label represent points.

Ir, Ru and Rh (condensation temper-

atures above 1324 K) are the most

important elements to get hints on their

origin

mass spectrometry and neutron

activation data are similar for Rh

contents, Ru/Ir and Pd/Ir ratios

Earth mantle; 1.2 ± 0.2 ng/g Rh; Ru/Ir

and Pd/Ir of about 2

distribution pattern of the Earth’s mantle

(red line) is close to enstatite chondrites

“The HSE in the mantle of Earth have been

delivered by a late meteoritic component.

Excesses in Pd, Ru, and Rh in the

terrestrial pattern make it impossible to

identify this component among known types

of meteorites.” Palme & O’Neill (2014)

Treatise on Geochemistry

Ru/Rh = 6.0 ± 0.7 for Earth mantle (n = 61)

Fischer-Gödde, Becker & Wombacher (2011) -

ratio is higher than for carbonaceous chondrites

(Ru/Rh = 5.4 ± 0.2, Tagle and Berlin 2008)

Ru/Rh for mantle rocks from Schmidt (2004) is

4.84 ± 0.98, in the range for non-carbonaceous

chondrites

Ru/RhEH = 4.85 (Tagle and Berlin, 2008)

Characteristic element ratios in the Earth mantle and various groups

of chondritic (undifferentiated) meteorites


Mean chondrite ratios from Tagle & Berlin (2008) Meteoritics & Planetary Science 43, 541–559. Mean CI ratio from Palme, Lodders

& Jones (2014) Treatise on Geochemistry. Earth’s mantle ratios; Schmidt (2004) Meteoritics and Planetary Science 39, 1995-

2007; Fischer-Gödde, Becker & Wombacher (2011) Chemical Geology 280, 365 - 383.

Earth’s mantle element mass ratios are similar to EH chondrites

Commas in table

represent points

Earth's mantle Pt/Rh Pd/Rh Ru/Rh Ir/Rh Ru/Ir Pt/Ir Pt/Os

(1) 5,65 4,42 6,00 2,94 2,29 1,90 1,69

(2) 6,58 4,79 4,84 2,41 2,01 2,74 2,91

Non carbonaceous

chondrites

H 6,78 3,59 4,93 3,26 1,52 2,08 1,94

L 6,19 3,69 4,49 3,01 1,49 2,06 1,91

LL 6,15 4,35 4,54 2,92 1,55 2,10 1,94

EH 6,19 4,86 4,85 3,00 1,62 2,06 1,83

EL 6,16 4,01 4,49 3,06 1,53 2,01 1,81

mean 6,29 4,10 4,66 3,05 1,54 2,06 1,89

1σ 0,27 0,52 0,22 0,13 0,05 0,03 0,06

Carbonaceous chondrites

CI 7,01 4,24 5,23 3,55 1,47 1,97 1,87

CM 6,99 4,08 5,72 3,81 1,50 1,84 1,65

CV 6,90 3,38 5,50 3,63 1,52 1,90 1,79

CK 7,32 3,52 5,26 3,62 1,45 2,02 1,89

mean 7,06 3,81 5,43 3,65 1,49 1,93 1,80

1σ 0,18 0,42 0,23 0,11 0,03 0,08 0,11

(1) Fischer-Gödde et al. (2011), mass spectrometry (n = 65, except Ru; 61 samples, except Pt; 64

samples ), 2 g aliquots

(2) Schmidt (2004), neutron activation analysis (n = 13, except Pt; 9 samples), 10 to 20 g aliquots

of homogenized sample powders, ground in agate mill to grain size < 50 μm

Ruthenium isotopic evidence for an inner Solar System origin of the late veneer


(a) ε100Ru data for chondrites, iron meteorites and terrestrial

chromitites. Shown are individual data points for all analysed samples

and the average neutron-capture-corrected ε100Ru for IAB iron

meteorites. The shaded areas represent the mean values for ordinary

and enstatite chondrites.

Figures from Fischer-Gödde & Kleine (2017) Nature 541

(b) The magnitude of ε100Ru anomalies increases with increasing distance

(in astronomical units, AU) from the Sun. More reduced materials like

enstatite and ordinary chondrites have less negative ε100Ru compared to

more oxidized and volatile-rich materials such as carbonaceous

chondrites that formed at greater heliocentric distance.

(a)

(b)

No ε100Ru data for LL chondrites availiable

Є100Ru = [(100Ru/101Ru)sample/(100Ru/101Ru)standard -1] ×10,000

Ir/Rh mass ratio of chondrites as an indicator for the

heliocentric distance of the formation region


Є100Ru data from Fischer-Gödde & Kleine (2017) Nature 541. Earth’s mantle Ir/Rh (2.92 ± 0.26, 1σ population

standard deviation, n=57), Fischer-Gödde, Becker & Wombacher (2011) Chemical Geology 280, 365 - 383.

CI abundances from Palme, Lodders & Jones (2014) In Holland & Turekian (Eds.) Treatise on

Geochemistry, Elsevier, Oxford,15–36. Mean chondrite abundance data from Tagle & Berlin (2008)

Meteoritics & Planetary Science 43, 541–559. Ir/Rh data for R, EH, EL chondrites (orange colour) from

Fischer-Gödde, Becker & Wombacher (2010) Geochimica et Cosmochimica Acta 74, 356–379.

The Ir/Rh mass ratios as an indicator for the

heliocentric distance increases with increasing

ε100Ru anomalies.

More reduced materials like enstatite and ordinary

chondrites have less values compared to more

oxidized and volatile-rich materials such as

carbonaceous chondrites that formed at greater

heliocentric distance.

Red and blue symbols are data from individual

meteorite samples (Fischer-Gödde & Kleine 2017).

Other symbols represent Ir/Rh mass ratios from mean

chondrite groups (Tagle & Berlin 2008) combined with

mean Є100Ru data (Fischer-Gödde & Kleine 2017).

Commas in figure represent points. No ε100Ru data for LL chondrites availiable. Correlation R2 = 0.85 (n=9) calculated for individual meteorite samples (no chondrite groups) and mantle values.

ε100Ru = the parts per 10,000 deviation

of the 100Ru/101Ru ratio from the

terrestrial standard value

Є100Ru = [(100Ru/101Ru)sample/(100Ru/101Ru)standard -1] ×10,000

Formation region of chondrites and the Earth’s “late veneer”

Re, Os, Ir, Ru, Rh, Pt, Pd, Au

The young sun is surrounded by a rotating disk of gas and dust (solar nebula) Through condensation and fractionation of the chemical elements in the solar nebula, the meteorite parent bodies of today's meteorites were formed Fractionation of metal condensates in meteorites

Modified after John A. Wood (1990)

„The New Solar System“ Cambridge University Press


Earth „late

veneer“

EH, EL Enstatite chondrites

H, L, LL Ordinary chondrites

CV, CO, CM, CI Carbonaceous chondrites

increasing Ir/Rh and ε100Ru with increasing heliocentric distance

Fractionated refractory elements in the Earth’s late accreted component by

gas-solid fractionation during condensation from a solar gas


Excess of refractory elements Rh and Ru and depletions in ultra-refractory elements Ir and Os

in mantle samples are consistent with a high-temperature gas condensation fractionation

process

Some portion of refractory siderophile elements (refractory metal alloys) removed from the

formation region by gravitational settling - as particles - to the nebular median plane as

proposed for chondrites, e.g., Ehman, Baedecker & McKown (1970), Larimer & Anders (1970),

Baedecker & Wasson (1975)

Depletion and fractionation of refractory elements in Earth’s late accreted component is likely

due to continuous loss of ultra-refractory nebular condensates from the formation region during

condensation as proposed in Schmidt (2004) and later confirmed by Fischer-Gödde, Becker &

Wombacher (2010) and Fischer-Gödde & Kleine (2017)

Condensation along with isolation of metal grains element abundances of Earth mantle

Gas-solid fractionation during condensation from a solar gas is one of the most important

process leading to fractionations in primitive objects of our solar system

(Wasson & Chou 1974, Baedecker & Wasson 1975, Wai & Wasson 1977)

Summary


(1) Ir/Rh element ratios correlate with Є100Ru values in chondrites

(2) Ir/Rh mass ratio as indicator for the heliocentric distance of the

formation region

(3) Earth's mantle has lowest Ir/Rh mass ratio compared with chondrites,

an indication that the formation of the "late veneer" has its origin more

close to the sun than enstatite chondrites

(4) Earth’s mantle - platinum group elements show continuous decrease

of abundances with decreasing volatility, a fingerprint for Nebular

processes, primarily fractionation during condensation

(5) The projectile from Clearwater East impact crater has their origin in the

innermost solar system

Future studies

• More high quality data of Rh (monoisotopic), Ir, Ru, etc. from various

planetary materials using different analytical methods

• meteorites, mars, moon, impact melts, asteroid sample return missions,

environmental samples should be obtained by neutron activation analysis

(i) TRIGA Mainz, Wien and FRM-II München (high neutron flux)

short irradiation facility for Rh, Ir, ...

(ii) CAMECA ims 1280-HR Heidelberg ion microprobe

high quality data of Rh, Ru and Ir might answer fundamental questions of

cosmochemistry and contribute to our understanding of the origin of the solar

system and the processes involved in the formation and unique composition

of planetary bodies

19 chemical elements have only a single stable isotope. Beryllium-9, Fluorine-19, Sodium-23, Aluminium-27, Phosphorus-31, Scandium-45, Manganese-55, Cobalt-59, Arsenic-75, Yttrium-89, Niobium-93, Rhodium-103, Iodine-127, Caesium-133, Praseodymium-141, Terbium-159, Holmium-165, Thulium-169, Gold-197


The Heidelberg ion probe (HIP) - Secondary Ionization Mass Spectrometry

(SIMS)

Figures from https://www.geow.uni-heidelberg.de/HIP/index_en.html

• CAMECA ims 1280-HR ion microprobe and peripheral instrumentation for pre- and post-analysis investigation of samples

• isotopic analysis of geochemically and cosmochemically solids at high spatial resolution and sensitivity

• isotope dating and measurement of trace elements in extraterrestrial and terrestrial rocks with high precision and spatial

resolution in the micrometer range

• Example of an application: „The total amount of C and H dissolved in the experimental glasses was determined using a Cameca IMS 1280 ion microprobe ...

A spot size of 10 µm in diameter was focused on by a beam of 133Cs+ ions with a 1- to 1.5-nA current and 12-kV energy and rastered

over a 30 µm by 30 µm area. Negatively charged ions were accelerated at 10 kV into a double-focusing mass spectrometer.”

Grewal D.S., Dasgupta R., Sun C., Tsuno K., Costin G. (2019) Delivery of carbon, nitrogen, and sulfur to the silicate Earth by a giant impact.

Science Advances 5, 1-12.

16th Rußbach School on Nucle ar Astrophysics, March 2019

Thank you for your attention

b. c.

e.

d.

f. g.

h.

January 21, 2019

January 21, 2017 January 5, 2017 January 6, 2017

January 21, 2017

i.

a. November 8, 2015

Mars

Venus Jupiter Galilean moons


Acknowledgements

Mars ?


I thank

Hans-Peter Gail

Katharina Lodders

Herbert Palme

&

Karl-Ludwig Kratz

for useful suggestions

Heidelberg at the beginning of the 22th century or at the end of the 21th century?

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Neutrons for Cosmochemistry Identification of Impacting ... · Neutrons for Cosmochemistry Identification of Impacting Asteroids Gerhard Schmidt Institute of Earth Sciences Heidelberg