Introduction into cosmochemistry - what the meteorites can tell us

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Introduction into cosmochemistry - what the meteorites can tell us www.kosmochemie.

1 Introduction into cosmochemistry - what the meteorites can tell us Wir erstaunen metallische und erdige Massen, welche der Außenwelt, den himmlischen Räumen angehören: betasten, wiegen, chemisch zersetzen zu können ; Alexander von Humboldt () Kosmos (vol. III, p., edition from, Verlag der J. G. Cotta schen Buchhandlung, Stuttgart)

0 Origin of meteorites most meteorites source from the asteroid belt meteorites are thought to come from Mars and from the Moon a single possibly came from Mercury (NWA 0)* Falls (~00): Observed

2 0 Origin of meteorites most meteorites source from the asteroid belt meteorites are thought to come from Mars and from the Moon a single possibly came from Mercury (NWA 0)* Falls (~00): Observed meteorite falls, quickly recovered, little terresitial alteration Finds (~00): Finds of ancient meteorites, those from the cold and hot deserts show only little terrestial alteration *Palme, H. (00) Science,, - 0 meteorite find in the Lybian desert

3 0 albedos of individual asteroids can related to certain types of meteorites 0 Meteorite classification

0 Differentiated meteorites from large parent

differentieated meteorites ( HED -group*) are

4 0 Differentiated meteorites from large parent bodies (with core formation) iron meteorites stone/iron meteorites stone meteorites (achondrites) pallasites iron meteorites mantle rocks? eucrites (basaltic crustal rocks) 0 differentieated meteorites ( HED -group*) are thought to come from the asteroid Vesta ( eucrite like albedo) *howardites, eucrites and diogonites

5 0 Undifferentiated meteorites (chondrites) no separation of metal and silicates (no core formation) source from small asteroids (T max < ~0 C) chondrites are primitive meteorites increasing aqueous increasing anhydrous alteration thermal metamorphism ~00-00 C ~0 C ~00 C CI CM/CR/... CV/CO/... CK ordinary chondrites are dry rocks LL L H LL L H LL L H LL L H Type- (CI or C): Chemically most primitive (e. g. Orgueil) LL L H T ~0 C 0 Orgueil CI carbonaceous chondrite fell May,, total mass ~ kg black color is due to ~- wt.% C (graphite, amorphous) contains wt.% H O (bond in minerals) one of five known CI chondrites (n = 000 meteorites)

6 0 What does chemically most primitive mean? volatile elements 0 Sun and CI meteorites have within ±-0% the same composition highly volatile elements are depleted in CIs

0 Sun contains >% of the mass of the solar system Sun s

have a composition representative for the bulk solar system = = =

Fe,Ni metal (~% Ni) cosmochmical classification of the elements

7 0 Sun contains >% of the mass of the solar system Sun s composition representative for the solar system CI chondrites have a composition representative for the bulk solar system = = = CI 0 decreasing T C Ca,Al-rich phases (CAIs) forsterite Mg SiO Fe,Ni metal (~% Ni) cosmochmical classification of the elements according to their condensation temperature see also Ebel and Grossman, GCA (000)

8 0 first major condensate is olivine (Mg SiO ) was identified in circumstellas dust disks ISO spectra, v. d. Ancker et al. (000) A&A, - 0 Element fractionation in CV chondrites depletion CV chondrites are systematically depleted in moderately volatile elements (fractional condensation)

$chondrites and planets (Earth, Mars, Mercury) established by fractional condensation inner solar system was heated to temperatures exceeding ~00 K first solids formed by condensation from the$

9 0 Composition of other carbonceous chondrites (major groups: CI, CM, CO, CK, CV) silicate T c (0%) 0 K K K K K K K K 0 Chemistry of terestial planets and asteroids composition of carbonaceous chondrites and planets (Earth, Mars, Mercury) established by fractional condensation inner solar system was heated to temperatures exceeding ~00 K first solids formed by condensation from the nebular gas

10 0 Composition of other carbonceous chondrites (major groups: CI, CM, CO, CK, CV) silicate T c (0%) 0 K K K K Cr in core K K K K 0 Formation & evolution of planetesimals planetesimals formed by accretion of material that formed by fractional condensation Earth accreted from material resembling that of carbonaceous chondrites bulk Earth is strongly depleted in the moderatly volatile elements (incl. H O, more than CV) result of position at AU element pattern of the silicate Earth indicates fractionation of Cr into the core no indication for Si in the core

0 Classification of chondrites type- chondrites do not contain water no or only little aqueous alteration of the type- parent body increasing aqueous alteration increasing anhydrous thermal

11 0 Classification of chondrites type- chondrites do not contain water no or only little aqueous alteration of the type- parent body increasing aqueous alteration increasing anhydrous thermal metamorphism ~00-00 C ~0 C ~00 C CI CM/CR/... CV/CO/... CK LL L H LL L H LL L H LL L H LL L H type-: Chemically most primitive (e. g. Orgueil) type-: Texturally most primitive (e. g. Vigarano, Semarkona) T ~0 C 0 Texturally primitive: agglomerates of material that is chemically and texturally in dis-equilibrium isolated olivine grain in Murchison (CM), from Pack et al., GCA, submitted FeO-poor olivine crystal (<% FeO) FeO-rich fine grained matrix material (~% FeO)

0 Components of chondrites ~ vol.% ~ vol.

material (chondrules) low-t (~00-00 K) material (sulphides, phyllosilicates,

12 0 Components of chondrites ~ vol.% ~ vol.% ~ vol.% pre-solar grains (extremely rare: diamonds, SiC, truely exotic) high-t (~00-0 K) condensates (CAIs, forsterites, metal grains) main components (ol, px, metal) material (chondrules) low-t (~00-00 K) material (sulphides, phyllosilicates, organics) * accretion * 0 chondrules Ordinary chondrit Chainpur (LL) ~0% chondrules ~% matrix reflected light micrography image map, width ~ cm

13 0 Carbonaceous chondrite Vigarano (CV) ~ vol.% chondrules, ~vol. % matrix, ~ vol.% CAIs CAI chondrules back scattered electron image map (Z contrast), width ~ cm 0 False color image of CR chondrite PCA

14 0 Pre-solar grains exotic grains of highly refractory phases (< µm) have extreme isotope anomalies result of stellar processes chondritic material is isotopically homogenuous even on smalles scale (only exception: oxygen) pre-solar SiC grain (from Ernst Zinner s webpage, Univ. of St. Louis) 0 Nd-isotope anomaly in presolar grain (SiC) from Palme and Jones (00)

$rare(<<%) highly refractory (diamond, SiC, corundum) pre-solar grains have inherited extreme isotope heterogeneity of the ISM material isotopic anomalies can be related to$

15 0 Extreme N and C-isotope anomalies in presolar grains (from Ernst Zinner s webpage, Univ. of St. Louis) 0 Pre-solar grains are truely exotic! rare(<<%) highly refractory (diamond, SiC, corundum) pre-solar grains have inherited extreme isotope heterogeneity of the ISM material isotopic anomalies can be related to stellar nucleosynthesis processes

$0 Æ Chondrite major components (I) Ca,Al-rich inclusions (CAIs) chondrules fine grained matrix material CAIs CAIs are rich in refractory elements (Ca, Al, Ti,.$

16 0 Æ Chondrite major components (I) Ca,Al-rich inclusions (CAIs) chondrules fine grained matrix material CAIs CAIs are rich in refractory elements (Ca, Al, Ti,...) formed by high-t fractional condensation (~0 K) from the nebula CAIs are the oldest material from the solar system. a old therefore: contain traces of extinct nuclides (e. g. Al, Mn) CAI from Vigarano (CV) enriched in Elements that condense at very high temperatures (~00 K) oldest s. s. material (. a)

17 0 Extinct nuclides in CAIs ( Al) Al Mg, t / = 000 a 0 Extinct nuclides in CAIs ( Al) initial Al/ Al ratio at the beginnig of the solar system (. a) was - - Number Al: Heat source of planetesimales

18 0 Chondrite major components (II) Ca,Al-rich inclusions (CAIs) chondrules fine grained matrix material Chondrules ( fiery rain, H. L. Sorby, ) chondrules are once molten droplets of silicate melt formed by a very short heating event (T max ~00 K) in a cool environment chondrules are ~- Ma younger than CAIs Chondrule (barred olivine + FeS) from Vigarano (CV) once molten droplets

19 Porphyric olivine chondrule (Renazzo, CR) 0 Chondrule formation by flash heating of dust balls precursor material (dust) chondrule

20 0 Chondrules are apparently ~- a younger than CAIs Assumption: Al was uniform in early solar system 0 Al data consistent with Pb-Pb absolute age data inner solar system had uniform Al distribution Al did not form close to the Sun ( X-point ) by irradiation 0

$most susceptible to aqueous alteration on the parent body represents the low-t fraction of chondrites Layered, accretionary rim of matrix material (Murchison,$

21 0 Chondrite major components (III) Ca,Al-rich inclusions (CAIs) chondrules fine grained matrix material Chondrite matrix very fine grained material (<- µm) most susceptible to aqueous alteration on the parent body represents the low-t fraction of chondrites Layered, accretionary rim of matrix material (Murchison, CM)

22 0 Age dating of matrix material Mn Cr, t / =. a, Mn/ Mn initial =. - matrix material (Kaba, CV) is ~ a younger than± CAIs dates the alteration on the meteorite parent body Mn/ Mn ratio was uniform in the early solar system Hua et al. (00) LPSC XXXIII 0 Are there unprocessed mineral condensates? Fe,Ni-Metall (Fe Ni ) forsteritic olivine (Mg SiO ) What were the conditions in the early solar system? metal/silicate equilibria can be used to quantify condensation temperature pressure (density) of the nebular gas oxygen fugacity (O/H-ratio)

23 0 Yes, there are! condensed Fe,Ni-metal grains zoning in Ni, Co, Cr, P and Si indicative for formation by gas/solid condensation false color image of a zoned metal grain (width ~ 00 µm, Schönbeck, 00) Refractory forsterite (Mg SiO ) condensate from Allende (CV)

24 0 Condensation signatures in single mineral grains from type- chondrites refractory forsterite extremely high contents of Ca, Al, Ti * temperature time (~days to years) *from Pack et al., MAPS, submitted 0 Ongoing project on forsterite condensates* quantification of temperatures, pressures and O/Hratios in the early solar system forsterite condensates (unlike metal condensates) present in all types of chondrites (carbonaceous, ordinary, R-chondrites) T, p, O f map of the early solar system (FU-Orionis/T- Tauri phase) distribution of O in the solar system *collaboration with H. Palme (Köln), H. St. C. O Neill (Canberra), H. Yurimoto (Tokyo) and E. Deloule (Nancy)

25 END iron meteorite with shiny fusion crust (width ca. cm)

Meteorites free samples from the solar system

Meteorites free samples from the solar system It is easier to believe that Yankee professors would lie, than that stones would fall from heaven [Thomas Jefferson, 3rd president of the USA] 2.1 Collection