Recent Advances in Meteoritics and Cosmochemistry · McSween et al.: Recent Advances in Meteoritics...

McSween et al.: Recent Advances in Meteoritics and Cosmochemistry 53

53

Recent Advances in Meteoritics and Cosmochemistry

Harry Y. McSween Jr.University of Tennessee

Dante S. LaurettaUniversity of Arizona

Laurie A. LeshinArizona State University

Major advances in research on extraterrestrial materials (meteorites, micrometeorites, inter-planetary dust particles, and presolar grains) since the first edition of Meteorites and the EarlySolar System are highlighted. Topics include the importance of newly recognized meteoritegroups; new discoveries about the presolar and nebular components of chondrites and inter-planetary dust particles; improvements in early solar system chronology using short-lived radio-nuclides; new insights into cosmochemical abundances, fractionations, and nebular reservoirs;and advances in reading nebular and prenebular records through a haze of secondary parent bodyprocesses. Some significant new insights based on these data are that the early solar systemexperienced a bewildering variety of nucleosynthetic inputs, the nebula was a dynamic entitywith transient heating events, and the system of planetesimals and planets evolved more rapidlythan previously appreciated.

1. INTRODUCTION

The goal of the first edition of Meteorites and the EarlySolar System (Kerridge and Matthews, 1988) was to inter-pret the meteoritic record in terms of constraints on theo-ries of the origin and early evolution of the solar system.That is also the intent of this volume. Here we briefly high-light significant new discoveries in meteoritics and cosmo-chemistry since the publication of the first edition. Thefollowing chapters will explain in more detail how thesebreakthroughs have constrained our understanding of pro-cesses and events prior to and within the early solar sys-tem. The breakthroughs introduced here are assigned to ep-ochs, following the general organization of the book.

We acknowledge that our choices of critical advances inmeteoritics and cosmochemistry are subjective but, we be-lieve, defensible. In citing literature, we have focused onoriginal discovery papers or, in some cases, comprehensivereviews. To make this task tractable, we consider researchon meteoritic samples per se and do not review the consid-erable progress made in providing geologic context throughthe identification and study of their asteroid or cometaryparent bodies. A comprehensive treatment of advances inasteroid spectroscopy, spacecraft encounters with asteroids,and mechanisms for the delivery of meteorites from aster-oids to Earth can be found in a recently published compan-ion volume, Asteroids III (Bottke et al., 2002). Likewise, thecontext and insights provided by new astrophysical theoryand astronomical observations are not catalogued here, butwill be considered in other chapters. Given that the presentvolume is not concerned with later planetary evolution, we

omit martian and lunar meteorites from consideration, ex-cept where they bear on the timing of planet accretion andearly differentiation.

2. EXTRATERRESTRIAL MATERIALSAVAILABLE FOR STUDY

2.1. Newly Recognized Chondrite Groups

Meteorite classification attempts to document differencesand linkages among meteorites — a critical first step be-cause variations and trends among members of a group canreveal the processes that produced them. In the first edition,9 groups of chondrites, 4 groups of achondrites, 2 stony-iron groups, and 13 iron meteorite groups were recognized.Other anomalous meteorites (distinct individual specimensor groups having less than five members) were also known.Since that time, new meteorites found in Antarctica and hotdeserts have considerably expanded our collections, and arecent compilation of meteorites (including ungrouped sam-ples, clasts in breccias, and micrometeorites) suggested thatperhaps ~135 asteroidal parent bodies may be represented(Meibom and Clark, 1999).

Several new classes of chondrites — one distinct chon-drite group (the Rumuruti or R group) and four carbona-ceous chondrite groups (CR, CH, CB, CK) — have beendefined. The R chondrites (Bischoff et al., 1993; Rubinand Kallemeyn, 1994; Schulze et al., 1994; Kallemeyn etal., 1996) are the most highly oxidized anhydrous chon-drite group, containing no metal and high olivine fayalitecontents, with fewer chondrules than ordinary chondrites

54 Meteorites and the Early Solar System II

(Fig. 1). The CR (Weisberg et al., 1993), CH (Grossmanet al., 1988; Scott, 1988), and CB (Weisberg et al., 2001)groups are among the most primitive types of chondrites(Krot et al., 2002a). These chondrites have large amountsof metal, but are classified as carbonaceous based on chem-istry and O isotopes. The CK group (Kallemeyn et al., 1991)contains the most highly metamorphosed carbonaceouschondrites. However, Greenwood et al. (2003) have ques-tioned whether CK and equilibrated CV chondrites are re-ally distinct groups, and Rubin et al. (2003) suggested thatthe CB chondrite designation may be misleading becausethat group may have formed by nonnebular processes.

Several remarkable chondrites that have proved difficultto classify have been described as well. The newly recov-ered Tagish Lake meteorite (Brown et al., 2000), a carbona-ceous chondrite of uncertain affinity, contains volatile-ele-ment abundances straddling those of CI and CM chondrites(Mittlefehldt, 2002), along with chondrules and inclusionssimilar to those in CM chondrites (Simon and Grossman,2003). However, Tagish Lake experienced a more perva-sive alteration history than CMs. Anomalous ordinary chon-drites of very low metamorphic grade and containing largequantities of refractory inclusions have also been described(Kimura et al., 2002).

2.2. Newly Recognized Achondrite Groups

Primitive achondrites, which were not distinguished fromachondrites (crystallized melts) in the first edition, are nowgenerally recognized to be residues from partial melting(Goodrich and Delaney, 2000). The major-element compo-sitions of most primitive achondrites are approximatelychondritic, but elements residing in minerals with low melt-ing points and incompatible trace elements that are concen-trated in partial melts have been depleted in them. Someprimitive achondrites have experienced higher degrees ofmelting, so that they no longer retain chondritic major-ele-ment compositions, and other primitive achondrites have

experienced such low degrees of melting that they retainrelict chondritic textures. However, we favor applying theclassification to all residues from partial melting, regard-less of the degree of melting. Iron/magnesium/manganesesystematics provide an effective means of distinguishingprimitive achondrites and (igneous) achondrites (Goodrichand Delaney, 2000). Newly classified groups of primitiveachondrites include the acapulcoites-lodranites (Fig. 2) (Mc-Coy et al., 1996, 1997), brachinites (Nehru et al., 1992), andwinonaites (Benedix et al., 1998). Ureilites, although not anewly defined group, are now also recognized as primitiveachondrites, and the complementary basaltic component forthese residues occurs as plagioclase-bearing clasts (Kita etal., 2004).

Among the achondrites, angrites (Mittlefehldt and Lind-strom, 1990) constitute a newly defined group due to theaddition of new meteorites. These basaltic meteorites aredominated by high abundances of refractory elements andlow oxidation state. A few lunar and martian meteorites (allachondrites) were recognized prior to publication of the firstedition, but not discussed in that volume; the numbers ofthese meteorites have markedly increased. The discovery thatthe NWA 011 basaltic achondrite (Fig. 3) has distinct Fe/Mnand O isotopes from otherwise similar eucrites (Yamaguchiet al., 2002) demonstrates that multiple differentiated aster-oids yielded basaltic meteorites.

3. THE PRESOLAR EPOCH

3.1. Presolar Grains

The study of minute stardust grains found in the fine-grained (matrix) portions of chondrites has burgeoned sincethe first edition, owing to the isolation of these grains inthe laboratory and their analysis using the ion microprobe.The phases most intensely studied are diamond, siliconcarbide, graphite, corundum, spinel, silicon nitride, andhibonite (Anders and Zinner, 1993; Ott, 1993; Bernatowicz

Fig. 1. Photomicrograph of the Dar al Gani 013 Rumaruti chon-drite (width of section = 36 mm), showing the brecciated texturethat is common in these meteorites. Large clasts at the upper cen-ter and right are impact melts, whereas other clasts are unmeltedbut show different degrees of thermal metamorphism. Courtesyof A. Bischoff, University of Münster.

Fig. 2. Photomicrograph of Acapulco, a primitive achondrite(acapulcoite) (width of section = 4.7 mm), showing its thoroughlyrecrystallized texture. Courtesy of T. McCoy, Smithsonian Insti-tution.


and Zinner, 1997; Zinner, 1998; Hoppe and Zinner, 2000;Nittler, 2003). Titanium carbide and FeNi metal occur asminute inclusions within presolar graphite grains (Fig. 4).All these phases are refractory, and the carbon-bearingphases formed under reducing conditions. Presolar silicateshave also now been recognized in both interplanetary dustparticles (Messenger et al., 2003) and chondrites (Nguyenand Zinner, 2004).

The exotic nature of presolar grains is demonstrated bytheir isotopic compositions, the diversity of which pointstoward formation in multiple stellar environments. For ex-ample, the carriers of the 22Ne-rich components Ne-E(L)and Ne-E(H) (released at low and high temperatures respec-tively), which provided the first hint that chondrites con-tained interstellar materials, have now been identified asgraphite (Amari et al., 1990) and SiC (Lewis et al., 1990),respectively. The morphologies and microstructures of pre-solar grains also reveal information on the conditions of dustformation in stellar regions (Bernatowicz et al., 1996, 2003).Lack of sputtering effects and the possibility of organicsurface coatings suggest mantles of ice may have protectedSiC grains in the interstellar medium (Bernatowicz et al.,2003). Presolar grains occur in the matrices of all chondritegroups in varying proportions (Huss and Lewis, 1995).

Isotopic analyses of interstellar grains have providedrigorous tests of models for nucleosynthesis and evolutionin red giants, asymptotic giant branch (AGB) stars, super-novae, and novae (Bernatowicz and Zinner, 1997; Zinner,1998; Nittler, 2003). These data provide stunning confirma-tions of predictions of the products of s-process nucleosyn-thesis, although no pure r-process pattern has yet beenfound in presolar grains. These grains also provide informa-tion on galactic chemical evolution. For example, isotopesof Si and Ti in silicon carbide do not conform to predictionsfor stellar nucleosynthesis and are thought to reflect rangesof initial composition of parent stars (Alexander and Nittler,1999).

3.2. Interplanetary Dust Particles

Tiny interplanetary dust particles (IDPs), collected in thestratosphere by aircraft, were described in the first edition.Advances in microanalytical technology have allowed im-proved characterization of these very small meteoritic ma-terials (Rietmeijer, 1998). Interplanetary dust particles sam-ple, at least in part, parent bodies distinct from those ofmacrometeorites.

The first edition focused on the mineralogies, textures,and optical properties (from transmission spectra) of IDPs.More recent research indicates that most IDPs are moreprimitive than CI chondrites. Bradley et al. (1996) obtainedthe first reflectance spectra of anhydrous IDPs, for whichthere are no meteorite counterparts. They suggested thatthese IDPs are samples of primitive P or D asteroids in theouter main belt. Some anhydrous IDPs are probably fromcomets (Brownlee et al., 1995).

Detailed studies reveal that anhydrous IDPs containabundant (organic) molecular cloud material and silicatestardust (Messenger, 2000; Messenger et al., 2003). Glasswith embedded metal and sulfide (GEMS) (Fig. 5) are an-other interesting component of IDPs (Bradley, 1994). Thesegrains have appreciable radiation histories, as expected ifthey once resided in the interstellar medium, so they maybe the irradiated remnants of cosmically abundant presolarsilicate grains. However, very few GEMS have anomalous

Fig. 3. Photomicrograph of Northwest Africa 011, a unique ba-saltic achondrite consisting mostly of large pigeonite grains in agroundmass of pigeonite and plagioclase (plain polarized light,width of field = 5.2 mm). Courtesy of A. Yamaguchi, NationalInstitute of Polar Research.

Fig. 4. Ultrathin section of presolar graphite, containing a 70-nm-long crystal of TiC that served as a nucleation center for con-densation of graphite in the outflowing gas around an AGB star.The graphite structure is concentric layers, and the radial spokesare an electron diffraction effect. Courtesy of T. J. Bernatowicz,Washington University.


O isotopic compositions (Messenger et al., 2003) of themagnitude of other presolar oxides (Nittler et al., 1997).

3.3. Organic Compounds

The structure and stable isotopic composition of organiccompounds in chondrites reflect complex interstellar, nebu-lar, and planetary processes whose resolution may be con-founded by terrestrial contamination (Gilmour, 2003). Thefirst edition focused on abiotic synthesis mechanisms in-ferred for the most extensively studied organic compoundsin CM carbonaceous chondrites.

Compound-specific stable-isotope measurement on me-teoritic organic matter is a significant new development. TheD/H enrichment of bulk organic matter, described in the firstedition, has now been measured in amino and sulfonic acids(Cooper et al., 1997) and suggests synthesis by ion-mole-cule reactions in the interstellar medium. Enrichment of 33Sin sulfonic acid is attributed to UV irradiation in an inter-stellar environment (Cooper et al., 1997). Values of δ13Cin low-molecular-weight compounds become more positiveas the amount of C in the molecule increases, whereas theopposite trend is observed in high-molecular-weight com-pounds (Sephton et al., 1999, 2000). These are kinetic sig-natures of both bond formation (synthesis from simplercompounds) and bond destruction (cracking of higher ho-mologs to form lower ones). Such trends may suggest thatthe carbon skeletons formed within icy mantles on inter-stellar grains, where radiation-induced reactions create anddestroy organic matter.

A significant discovery concerning organic compoundsis the determination that nonbiogenic amino acids are pres-ent as nonracemic mixtures in carbonaceous chondrites.Small but measurable excesses of the L-enantiomers ofamino acids have been demonstrated to have a nonbiologic(Cronin and Pizzarello, 1997) and nonterrestrial (Engel andMacko, 1997) origin. How slightly optically active organiccompounds would be produced in the interstellar mediumis not understood, but selective destruction of one enanti-omer by UV circularly polarized light from neutron starsin a presolar cloud has been invoked. Hydrocarbons withlarge H- and N-isotopic anomalies in anhydrous IDPs likelyformed in molecular clouds (Keller et al., 2004), althoughorganic matter occurs in comparable abundance in hydratedIDPs (Flynn et al., 2003).

4. THE DISK FORMATION EPOCH

4.1. Presolar Grain Survival and Chronology

Because of destructive oxidation reactions, the lifetimesof presolar SiC grains exposed to a hot nebula are shortcompared to nebula cooling timescales (Mendybaev et al.,2002). Attempts to date presolar silicon carbide grains basedon the production of spallogenic 21Ne give surprisingly lowages of ~10–130 Ma (Tang and Anders, 1988). However,recoil experiments suggest that micrometer-sized SiC grainswill have lost virtually all Ne produced in the interstellarmedium (Ott and Begemann, 2000), casting doubt on theseages.

4.2. Nebular Elemental and Isotopic Abundances

Anders and Grevesse (1989), Lodders (2003), and Palmeand Jones (2003) compiled new average solar system ele-mental and isotopic abundances for CI chondrites. Thesewere compared with solar photosphere compositions, whichhave also been updated (Palme and Jones, 2003, and refer-ences therein). The solar O abundance has been revised down-ward by 50% and the C abundance by a smaller amount(Allende Prieto et al., 2001), leading to a higher C/O ratioand thus somewhat more reducing nebular gas than envi-sioned in the first edition (Allende Prieto et al., 2002). Therehave also been significant downward revisions in S, Se, andP, and new solar abundances of light elements support theprevious conclusion that Li is depleted in the Sun.

The smoothness of heavy-element abundance patternswas formerly used to support the choice of CI chondritesin determining solar system abundances; however, somemeasured discontinuities are real (Burnett et al., 1989) sothis reasoning is flawed. The recognition that sulfate veinsin Orgueil probably formed during the meteorite’s residenceon Earth (Gounelle and Zolensky, 2001) suggests open-sys-tem modification of soluble components like S. The TagishLake meteorite has been suggested to be a better proxy forsolar system abundances than CI chondrites (Brown et al.,2000; Zolensky et al., 2002).

Fig. 5. Brightfield transmission electron micrograph of glasswith embedded metal and sulfides (GEMS) within a thin section ofan interplanetary dust particle. GEMS are composed of rounded,nanometer-sized kamacite and pyrrhotite crystals in Mg-rich sili-cate glass. The properties of GEMS appear to have been shaped bychronic exposure to ionizing radiation, and they resemble amor-phous silicates in the interstellar medium. Courtesy of J. Bradley,Lawrence Livermore National Laboratory.


4.3. Isotopic Reservoirs

The slope of the O-isotope mixing line for bulk refractoryinclusions (calcium-aluminum-rich inclusions, or CAIs) is~0.95, but new microanalyses of inclusions suggest a slopeof 1.00 (Young and Russell, 1998). The distinction is impor-tant for distinguishing between competing mechanisms forproduction of a 16O-rich reservoir. One interpretation is thatthis reservoir represents a nucleosynthetic enrichment in thenebula, possibly inherited from a nearby supernova. An al-ternative hypothesis is mass-independent fractionation of16O (Thiemens, 1996), perhaps through self-shielding of COin the nebula (Clayton, 2002). A 0.95 slope would rule outthe possibility of mass-independent chemical fractionation ofO isotopes in the nebula, but either mechanism is permittedby a 1.00 slope (Ireland and Fegley, 2000). Analyses of Oisotopes in condensate olivines in amoeboid olivine aggre-gates (AOAs) suggest a 16O-rich nebular gas (Krot et al.,2002b), whereas chondrules generally formed in equilibriumwith a more 16O-poor gas. The 16O-rich gas may have re-sulted from mass-independent fractionation or evaporationof dust-enhanced regions.

5. THE FIRST NEBULAR EPOCH

5.1. Nebular Chronology and Origin ofShort-lived Radioisotopes

The first edition included seven chapters on chronology,reflecting the importance of understanding the temporalsequence and duration of early solar system events andprocesses. The most significant new advance in meteoritegeochronology is the development of new high-resolutionchronometers based on short-lived radionuclides. The sixextinct radionuclides discussed in the first edition have nowbeen augmented by meteorite dating techniques based on10Be-10B, 41Ca-41K, 60Fe-60Ni, 146Sm-142Nd, 182Hf-182W,92Nb-92Zr, 187Re-187Os, and 107Pd-107Ag (McKeegan andDavis, 2004). A major challenge in using these isotopic sys-tems is in understanding how they were produced, whichbears on what events are actually dated.

Significant advances have been made in the 53Mn-53Cr(Lugmair and Shukolyukov, 2001) system, which appears tobe a useful chronometer despite evidence that 53Mn was notdistributed homogeneously in the nebula. This chronometerdates fractionation of Mn from Cr, due primarily to Mn vol-atility (Palme, 2001). However, 53Mn data have found avariety of applications, such as constraining the timing ofaqueous alteration to form carbonates in carbonaceous chon-drites to <20 m.y. after accretion (Endress et al., 1996).

Considerable attention has also been focused on 26Al-26Mg. The idea that 26Al was homogenously distributed inthe neb-ula (MacPherson et al., 1995) has been challengedby argu-ments that it was produced by local irradiation inan X-wind region of the early Sun (Gounelle et al., 2001).If refractory condensates incorporated this nuclide and werethen dispersed, the canonical 26Al/27Al ratio would not ap-

ply to other nebular materials, perhaps explaining an appar-ent age difference of several million years (based on 26Al)between CAIs and chondrules. However, this age differenceis supported by 53Mn and 129I data (Swindle et al., 1996)and very precise Pb-Pb ages (Amelin et al., 2002) for CAIsand chondrules.

As noted in the first edition, short-lived radionuclidechronometers commonly show inconsistent timescales, aproblem that has not yet been fully resolved. However, 129I-129Xe dates for unshocked meteorites can now be reconciledwith 26Al and 53Mn chronologies (Gilmour et al., 2000).

The age of the solar system is now based on a combina-tion of long- and short-lived chronometers applied to refrac-tory inclusions in chondrites. 235U/238U-207Pb/206Pb ages of4566 Ma for Allende CAIs (Allègre et al., 1995) and 4567 Mafor Efremovka CAIs (Amelin et al., 2002) may be a lowerage limit if the inclusions were altered. This age is slightlyolder than the 4559-Ma estimate in the first edition. Lug-mair and Shukolyukov (2001) defined lower (4568 Ma) andupper (4571 Ma) age limits, based on constraints from53Mn-53Cr, in agreement with the upper limit for the CAI207Pb-206Pb age and with 26Al and 129I data for the ordinarychondrite Ste. Marguerite.

Unambiguous evidence of three especially importantextinct radionuclides has been discovered since the firstedition. Two of these bear directly on the question of thesources of short-lived nuclides, with apparently contradic-tory implications. The finding of live 10Be in CAIs (McKee-gan et al., 2000) is important because this nuclide is notproduced via nucleosythesis in stars and thus is generallyinterpreted to be evidence for local production of at leastsome short-lived isotopes by spallation reactions in the neb-ula. However, 10Be and 26Al are decoupled in many CAIs(Marhas et al., 2002), suggesting that 26Al was not a prod-uct of spallation. Evidence in meteorites for live 60Fe (Shu-kolyukov and Lugmair, 1993; Tachibana and Huss, 2003),which is only formed through stellar nucleosynthesis, alsocontradicts the idea that all short-lived radioactivities werelocally produced. These nuclides were probably producedin stars and imported within presolar grains (MacPhersonet al., 2003). Finally, with a half-life of 103 Ka, 41Ca is theshortest-lived isotope yet confirmed to be present in chon-drites (Srinivasan et al., 1994). This age constrains the time-scale from synthesis to injection of short-lived isotopes tobe very short.

5.2. Nebular Condensates and Residues

The requirement for a hot nebula to allow vaporizationand condensation, a popular idea in the first edition, has nowbeen circumvented by models in which heating of the diskoccurs close to the protosun and the materials are redistrib-uted outward (the X-wind model). Shu et al. (1996) de-scribed a scenario in which various chondrite componentsmight have been formed far from the positions of their ac-cretion into chondrites. The existence of 10Be in CAIs (Mc-Keegan et al., 2000), not formed during stellar nucleosyn-


thesis, has been taken as support for the X-wind model.However, there are still many proponents of the hot nebulahypothesis, which is consistent with models and observa-tions of the earliest era of disk formation when mass accre-tion rates were high (e.g., Bell et al., 2000). Regardless ofwhich model is advocated, it is clear that we envision amore dynamic nebula with transient heating events.

Refractory inclusions (CAIs) were described in the firstedition as nebular condensates, commonly modified bymelting, recrystallization, and alteration (Fig. 6). These an-cient objects are now generally understood to be mixtures ofcondensate materials and refractory residues from evapora-tion (Ireland and Fegley, 2000). High-temperature conden-sation is required to produce the observed fractionations inrefractory trace elements, whereas the widespread persis-tence of mass-dependent isotopic fractionation in refractoryelements such as Mg and Si indicates evaporation (Gross-man et al., 2002). It is now recognized that the large CAIsin Allende have been extensively processed after accretionand are not representative of CAIs in other meteorite classes.Calcium-aluminum-rich inclusions in other chondrite groupshave now been characterized (MacPherson, 2003).

Amoeboid olivine aggregates (AOAs) are the most com-mon type of refractory inclusions in many types of carbona-ceous chondrites. Detailed studies of AOAs, which providea compositional link between CAIs and chondrules, indicatethey are clumps of lower-temperature nebula condensatesthat originated in a 16O-rich gaseous reservoir (Krot et al.,2002b). Smooth, concentric zoning of some FeNi metalgrains in primitive CH chondrites suggests their formationby gas-solid condensation (Meibom et al., 1999). Thesegrains (Fig. 7) may be the first documented metal conden-sates.

5.3. Nebular Chemical Fractionations

Cosmochemical behavior is dominated by element vola-tility, presumably reflecting either incomplete condensationor evaporation. The refractory elements are always assumedto be present in chondritic (CI) relative proportions; how-ever, two cases have now been shown to violate this as-sumption. Refractory Re/Os ratios in carbonaceous chon-drites are systematically lower than those in ordinary andenstatite chondrites (Walker et al., 2002), and Nb/Ta ratiosin chondrites are variable (Weyer et al., 2003).

Moderately volatile elements are depleted in achondriteparent bodies and in planets, relative to chondrites. How-ever, measured 41K/39K ratios among the terrestrial planets,the Moon, achondrites, and chondrites are uniform to within~2‰ (Humayun and Clayton, 1995). This lack of K-iso-tope fractionation has been argued to preclude evaporationas an explanation for the observed volatile depletions. How-ever, evaporation of nebular crystalline dust prior to its ac-cretion into planetesimals is possible (Young, 2000).

6. THE SECOND NEBULAR EPOCH

6.1. Chondrules

Four chapters in the first edition were devoted to chon-drules. New observational, experimental, and theoreticalstudies of chondrules have resulted in some changes, manyof which were detailed in Chondrules and the Protoplane-tary Disk (Hewins et al., 1996). The presence of C as a re-ducing agent in chondrule precursors produces character-istic mineralogical features of chondrules (Connolly et al.,1994). Melting intervals for chondrules, previously thought

Fig. 6. Backscattered electron image of a CAI in the Adelaidecarbonaceous chondrite. Corundum (cor) is replaced by hibonite(hib), which is in turn corroded by grossite (grs). The inferredcrystallization sequence is consistent with the equilibrium conden-sation at a total pressure ≤10–5 bar and ~1000 CI dust/gas enrich-ment relative to solar composition. Courtesy of A. Krot, Universityof Hawai‘i.

Fig. 7. X-ray elemental map in Ni Kα of a zoned FeNi metalgrain from the Hammadah al Hamra 237 carbonaceous chondrite.This metal grain is inferred to be a nebular condensate. Courtesyof A. Krot, University of Hawai‘i.


to have lasted for hours, are now restricted to a few min-utes, to allow retention of moderately volatile elements(Hewins, 1997). Moreover, volatile retention apparentlyrequires that chondrules could not have formed in the ca-nonical nebula, but must have formed by flash heating athigher pressures (Yu and Hewins, 1998). Many chondrulesappear to have experienced multiple heating events (Rubinand Krot, 1996), and most were not completely melted.Correlations between the relative ages, based on 26Al, andbulk compositions of chondrules (Mostefaoui et al., 2002)suggest that Si and volatile elements evaporated from chon-drule melts and then recondensed as precursors for the nextgeneration of chondrules. Experiments constrain peak tem-peratures to 1770–2120 K, and chondrule cooling rates weredecidedly nonlinear, very fast and then slow, consistent withshock melting (Desch and Connolly, 2002). The origin ofchondrules remains enigmatic, but thermal processing ofparticles in nebular shock waves appears to meet most con-straints imposed by chondrule properties (Ciesla and Hood,2002; Desch and Connolly, 2002).

6.2. Metal and Sulfide

Metal grains in ordinary chondrites, suggested to becondensates in the first edition, have apparently been modi-fied after accretion (Zanda et al., 1994). Sulfides in chon-drites are now understood to have formed by reaction ofmetal with the gaseous nebula. Lauretta et al. (1997) de-termined that corrosion of FeNi metal by H2S produces Fe-bearing sulfides rapidly enough to occur within the lifetimeof the nebula, and showed that sulfides produced in this wayare morphologically similar to those in chondrite matrix.

6.3. Matrix

The mineralogy of chondrite matrices has become in-creasingly well characterized by application of transmissionelectron microscopy. Matrix is most easily studied in carbo-naceous chondrites (Buseck and Hua, 1993), where it is mostabundant. New descriptions of matrix in the most primitivecarbonaceous chondrites reveal amorphous silicate material,forsterite, and enstatite, with minor carbonaceous, refrac-tory, and presolar materials — apparently mixtures of nebu-lar materials and interstellar grains. Hydrothermal alterationof such matrix has produced the matrices of most carbona-ceous chondrites. The mineralogy of interstitial matrix andrims on chondrules in unequilibrated ordinary chondrites(Brearley, 1996) is more complex, consisting mostly of oli-vine, sometimes with amorphous silicate material, and py-roxenes, feldspars, metal, a variety of spinels and sulfides,whitlockite, and various alteration phases.

6.4. Organic Compounds

The Tagish Lake meteorite’s fall and clean collectionunder subfreezing conditions make it a relatively uncon-taminated sample. The organic components of Tagish Lake

are dominated by soluble carboxyl and dicarboxyl com-pounds but few amino compounds. Its abundant aromaticcompounds have a more restricted distribution than thosein other carbonaceous chondrites (Pizzarello et al., 2001),possibly reflecting catalytic processes that tend to be moreselective than other synthetic pathways. Tiny, hollow or-ganic globules (Fig. 8) in Tagish Lake (Nakamura et al.,2002) are similar to material produced by laboratory simula-tion of UV photolysis of interstellar ice analogs.

Calculations support the idea that the soluble fraction ofthe organic compounds in chondrites formed during aque-ous alteration of parent bodies (Schulte and Shock, 2004).Some progress has been made in characterizing the insolu-ble macromolecular organic matter in carbonaceous chon-drites, cited as a daunting task in the first edition. Similaritiesamong macromolecules in CI and CM chondrites suggestthat essentially the same aromatic structural units were com-mon to all (Sephton et al., 1998, 2000). Cody et al. (2002)determined that this material in Murchison was 61–66%aromatic and that its aliphatic chains are highly branched.

6.5. Cosmogenic Nuclides

There is continuing disagreement over whether or notmeteorites show noble gas isotopic evidence of irradiationby an energetic early Sun (Woolum and Hohenberg, 1993;Wieler et al., 2000). As noted earlier, however, the discov-ery of the former presence of 10Be in refractory inclusions(McKeegan et al., 2000) attests to intense irradiation in theearly solar system. The production by spallation of othershort-lived radionuclides found in chondrites has also beensuggested (Gounelle et al., 2001); however, 10Be and 26Alare decoupled in many CAIs (Marhas et al., 2002). Someshort-lived nuclides appear to have been produced by spal-lation in the nebular, some by nucleosynthesis in other stars,and some possibly (but not necessarily) by both processes.

Fig. 8. TEM image of a hollow globule of organic matter (scalebar = 200 nm) in the Tagish Lake carbonaceous chondrite. Cour-tesy of K. Nakamura, Kobe University.


7. THE ACCRETION EPOCH

7.1. Mixing and Sorting of Nebular Components

Presolar grains constrain mixing between reservoirs inthe nebula. The average isotopic compositions of carbon andsilicon in SiC grains are the same among different meteor-ite groups, as would be expected if the nebula sampled awell-mixed reservoir of debris from various stars (Huss andLewis, 1995; Russell et al., 1997). The limited size distri-butions of chondrules are now explained as the result ofaerodynamic sorting in turbulent nebula eddies (Cuzzi et al.,1996; Kuebler et al., 1999).

7.2. Sampling Other Accreted Materials

Calculations of IDP orbital evolution show that the at-mospheric entry velocity of comet-derived dust is gener-ally higher than that of asteroid-derived particles. Entryvelocity controls the degree of atmospheric heating, which,in turn, affects the abundances of 4He (Nier and Schlutter,1993) and other volatile elements (especially zinc) (Kehmet al., 2002), as well as mineralogy (Greshake et al., 1998).These changes can potentially be used to identify IDPs ofcometary origin.

Micrometeorites are larger than IDPs and are commonlymelted partly or completely during atmospheric passage.The resulting cosmic spherules represent the peak in massdistribution of meteoritic materials accreted to Earth, so acomprehensive chemical study of them may provide a less-biased sampling of asteroid compositions than do meteor-ites. Most cosmic spherules have CM-chondrite-like com-positions (Brownlee et al., 1997).

8. THE PARENT BODY EPOCH

The nebular record in meteorites is commonly obscured,at least in part, by parent-body processes — thermal meta-morphism, aqueous alteration, melting, impact brecciation,and shock metamorphism. The first edition devoted six chap-ters to these topics, but ambiguities remained. Significantadvances in unraveling these geologic overprints in mete-orites now enable a better understanding of which materi-als and properties are of nebular origin and which are not.

8.1. Chondritic Parent Bodies

All asteroids have been heated to some degree, probablyby radioactive decay of short-lived nuclides such as 26Al(MacPherson et al., 1995; Russell et al., 1996; Srinivasanet al., 1999; Kita et al., 2000). Thermal evolution modelsbased on 26Al heating provide a context for interpretingmeasureable properties in chondrites — equilibration tem-peratures, cooling rates, and radiometric ages (McSween etal., 2002). These models are appropriate for bodies thatdevelop concentric metamorphic zones, and the existenceof such “onion-shell” asteroids has been demonstrated by

measuring the times of cooling for ordinary chondritesmetamorphosed at various peak temperatures (Göpel et al.,1994; Trieloff et al., 2003). Differences in 182Hf-182W and235U/238U-207Pb/206Pb ages (equal to 2–12 Ma for H chon-drites) have been used to estimate the interval of ordinarychondrite metamorphism (Humayun and Campbell, 2002).

The chondrite classification system based partly on ther-mal metamorphic grade was in wide use prior to the firstedition but the action of fluids, indicated by changes in oxi-dation state during ordinary chondrite metamorphism (Mc-Sween and Labotka, 1993), had not been recognized. Scalesquantifying the intensity of aqueous alteration (Browninget al., 1996) and shock metamorphism (Stöffler et al., 1991;Scott et al., 1992; Rubin et al., 1997) now allow effectsaccompanying these processes to be discerned. Noteworthyexamples are destruction of presolar grains (Huss, 1990),the redistribution of minor elements in chondritic metal dur-ing metamorphism (Zanda et al., 1994), and the synthesisof new organic compounds during aqueous alteration andheating (Sephton et al., 2003; Pearson et al., 2002). In thefirst edition, aqueous alteration was described only as a par-ent-body process, still a prominent view (Krot et al., 1995).However, other observations suggest some carbonaceouschondrite components may have been altered before accre-tion, either in the nebula or within small, precursor plane-tesimals (Metzler et al., 1992).

Halite-bearing clasts (Fig. 9) have been discovered inseveral recently fallen ordinary chondrite regolith breccias(Zolensky et al., 1999). Irradiation effects show that thesesalts are preterrestrial, and fluid inclusions demonstrate thatthey formed by precipitation from aqueous liquids at lowtemperatures in asteroid regoliths (Whitby et al., 2000).

Fig. 9. Halite crystals (3–4 nm) in the Zag ordinary chondritedemonstrate the former presence of evaporating fluids in asteroids.Courtesy of M. Zolensky, NASA Johnson Space Center.


8.2. Differentiated Parent Bodies

A new development in understanding achondrite mag-matism is evidence supporting that eucrites and related di-ogenites may have formed in a magma body of asteroidalscale (Righter and Drake, 1997; Ruzicka et al., 1997).However, despite extensive petrographic and geochemicalstudies, there is still little consensus on major questions ofeucrite petrogenesis (Mittlefehldt et al., 1998). Angritesprovide an interesting comparison with eucrites, mimick-ing the dichotomy of alkaline and tholeiitic basalts on Earth(Mittlefehldt and Lindstrom, 1990). Angrites and eucriteshave similar O-isotopic compositions (Clayton and Mayeda,1996) and experiments suggest they could have been pro-duced by melting similar chondritic protoliths under dif-ferent redox conditions. The paucity of meteoritic basaltgroups relative to other differentiated meteorites might beexplained by explosive volcanism (Wilson and Keil, 1991).

Ureilites, the most perplexing primitive achondrites, wereformerly argued to be cumulates but are now generallyviewed as smelting residues (Goodrich, 1992; Walker andGrove, 1993; Singletary and Grove, 2003). Supporting theinterpretation that the ureilite parent body did not undergoextensive melting is the surprising finding that ureilites haveprimitive O-isotopic compositions that correlate with the Fecontents of olivine and pyroxene (Clayton and Mayeda,1988).

New information on Fe-Ni phase equilibria, such as arevised Fe-Ni phase diagram (Yang et al., 1996), has pro-vided an improved understanding of the cooling historiesof asteroid cores. An investigation of Ni-rich areas of wid-manstätten patterns in iron meteorites (Yang et al., 1997)indicated these are not taenite, as previously thought, butintergrowths of tetrataenite, martensite, and awaruite. Thisrevelation constitutes a drastic revision of iron meteoritemineralogy, and its implications for Fe-Ni phase relationsare not yet clear. Hopfe and Goldstein (2001) have signifi-cantly revised the metallographic cooling rate method.

The difficulties in segregating metallic liquids from hostsilicates have been clarified (Taylor, 1992). Numerical mod-els of fractional crystallization in irons have become moresophisticated, and now explore the effects of imperfect mix-ing, liquid immiscibility, and trapping of S-rich liquid (Haackand McCoy, 2003, and references therein). Application ofRe-Os dating has demonstrated that the cores represent-ing all the various iron meteorite groups crystallized within100 m.y. of each other (Smoliar et al., 1996; Shen et al.,1996).

9. THE PLANETARY EPOCH

9.1. Formation Chronology

The application of 182Hf-182W to iron meteorites andchondrites has constrained the early times of core forma-tion in asteroids (Lee and Halliday, 1997). A revision in theW-isotopic composition for chondrites (Kleine et al., 2002;

Schoenberg et al., 2002; Yin et al., 2002) significantly low-ered the formation ages of Earth (11–30 Ma) and Mars(<15 Ma) relative to the formation time of CAIs, suggestingrapid accretion and differentiation of the terrestrial planets.

9.2. Organic and Putative Biogenic Substances

Chyba and Sagan (1992) concluded that the dominantsource of organic material to the early Earth was IDPs,which are ~10% organics by mass, because their gentleatmospheric deceleration could deliver organic compoundsintact.

No review of advances in meteoritics or biogenic mol-ecules would be complete without mentioning ALH 84001,originally misclassified as a diogenite but recognized asa unique martian meteorite by Mittlefehldt (1994). If forno other reason, ALH 84001 is important as the oldest(~4.5 Ga) planetary sample (Nyquist et al., 2001). The pro-posal that this meteorite contains evidence of extraterrestriallife (McKay et al., 1996) generated a firestorm of contro-versy that placed meteoritics on the front pages of news-papers. The meteoritics community responded with an out-pouring of research on carbonates, nanophase magnetites,putative microfossils, and organic compounds. Althoughfew planetary scientists have accepted the proffered evi-dence for this hypothesis, its lingering effects are a revital-ized Mars exploration program focused on the search forlife, as well as a significant increase in the price of mete-orites. Scientific consequences include research on the for-mation and stability of polycyclic aromatic hydrocarbons,recognition of the difficulties in identifying potential min-eralogic or isotopic biomarkers and fossils, discovery ofnovel mechanisms for carbonate formation, and acknowl-edgment that terrestrial micro-organisms eventually con-taminate all meteorites (Steele et al., 2000).

9.3. Implications of Cosmic-RayExposure Ages

The large number of exposure ages for different mete-orite groups now available (Wieler and Graf, 2001; Herzog,2003) permits new insights into the orbital mechanics ofmeteoroids. The pronounced age clumps for various groupssuggest that a small number of collisions produced a largefraction of known meteorites. In the first edition, the reign-ing view was that Earth capture depended on impact injec-tion of meteoroids into chaotic resonances. However, thecalculations of Gladman et al. (1997) showed that trans-port through resonances took much less time than clockedby cosmic-ray exposure ages. The order-of-magnitude dis-crepancies have now been resolved by considering the roleof the Yarkovsky effect (small accelerations produced byasymmetric solar heating) in slowly moving meteoroids intoresonances (Farinella et al., 1998).

Acknowledgments. Thoughtful reviews by H. Palme and E.Zinner have improved this chapter. We also thank various indi-


viduals who provided images, each identified in the respectivecaptions.

REFERENCES

Alexander C. M. O’D. and Nittler L. R. (1999) The galactic chemi-cal evolution of Si, Ti and O isotopes. Astrophys. J., 519, 222–235.

Allègre C. J., Gerard M., and Göpel C. (1995) The age of theEarth. Geochim. Cosmochim. Acta, 59, 1445–1456.

Allende Prieto C., Lambert D. L., and Asplund M. (2001) Theforbidden abundance of oxygen in the sun. Astrophys. J. Lett.,556, L63–L66.

Allende Prieto C., Lambert D. L., and Asplaund M. (2002) Areappraisal of the solar photospheric C/O ratio. Astrophys. J.Lett., 573, L137–L140.

Amari S., Anders E., Virag A., and Zinner E. (1990) Interstellargraphite in meteorites. Nature, 345, 238–240.

Amelin Y., Krot A. N., Hutcheon I. D., and Ulyanov A. A. (2002)Lead isotopic ages of chondrules and calcium-aluminum-richinclusions. Science, 297, 1678–1683.

Anders E. and Grevesse N. (1989) Abundances of the elements:Meteoritic and solar. Geochim. Cosmochim. Acta, 53, 197–214.

Anders E. and Zinner E. (1993) Interstellar grains in primitivemeteorites: Diamond, silicon carbide and graphite. Meteorit-ics, 28, 490–514.

Bell K. R., Cassen P. M., Wasson J. T., and Woolum D. S. (2000)The FU Orionis phenomenon and solar nebular material. InProtostars and Planets IV (V. Manning et al., eds.), pp. 897–926. Univ. of Arizona, Tucson.

Benedix G. K., McCoy T. J., Keil K., Bogard D. D., and GarrisonD. H. (1998) A petrologic and isotopic study of winonaites:Evidence for early partial melting, brecciation, and metamor-phism. Geochim. Cosmochim. Acta, 62, 2535–2554.

Bernatowicz T. J. and Zinner E. K. (1997) Astrophysical Impli-cations of the Laboratory Study of Presolar Materials. Ameri-can Institute of Physics, New York. 750 pp.

Bernatowicz T. J., Cowsik R., Gibbons P. C., Lodders K., FegleyB., Amari S., and Lewis R. S. (1996) Constraints on stellargrain formation from presolar graphite in the Murchison mete-orite. Astrophys. J., 472, 760–782.

Bernatowicz T. J., Messenger S., Pravdivtseva O., Swan P., andWalker R. M. (2003) Pristine presolar silicon carbide. Geochim.Cosmochim. Acta, 67, 4679–4691.

Bischoff A., Palme H., Schultz L., Weber D., Weber H. W., andSpettel B. (1993) Acfer 182 and paired samples, an iron-richcarbonaceous chondrite: Similarities with ALH85085 and itsrelationship to CR chondrites. Geochim. Cosmochim. Acta, 57,2631–2648.

Bottke W. F. Jr., Cellino A., Paolicchi P., and Binzel R. P., eds.(2002) Asteroids III. Univ. of Arizona, Tucson. 785 pp.

Bradley J. P. (1994) Chemically anomalous, preaccretionally ir-radiated grains in interplanetary dust from comets. Science,265, 925–929.

Bradley J. P., Keller L. P., Brownlee D. E., and Thomas K. L.(1996) Reflectance spectroscopy of interplanetary dust parti-cles. Meteoritics & Planet. Sci., 31, 394–402.

Brearley A. J. (1996) The nature of matrix in unequilibrated chon-dritic meteorites and its possible relationship to chondrules. InChondrules and the Protoplanetary Disk (R. H. Hewins et al.,eds.), pp. 137–152. Cambridge Univ., Cambridge.

Brown P. G., Hildebrand A. R., Zolensky M. E., Grady M.,

Clayton R. N., Mayeda T. K., Taliaferri E., Spanding R.,MacRae N. D., Hoffman E. L., Mittlefehldt D. W., WackerJ. F., Bird J. A., Campbell M. D., Carpenter R., Gingerich H.,Glatiotis M., Greiner E., Mazur M. J., McCausland P. J.,Plotkin H., and Mazur T. R. (2000) The fall, recovery, orbit,and composition of the Tagish Lake metorite: A new type ofcarbonaceous chondrite. Science, 290, 320–325.

Browning L. B., McSween H. Y., and Zolensky M. E. (1996)Correlated alteration effects in CM carbonaceous chondrites.Geochim. Cosmochim. Acta, 60, 2621–2633.

Brownlee D. E., Joswiak D. J., Schlutter D. J., Pepin R. O., Bra-dley J. P., and Love S. J. (1995) Identification of individualcometary IDPs by thermally stepped He release (abstract). InLunar and Planetary Science XXVI, pp. 183–184. Lunar andPlanetary Institute, Houston.

Brownlee D. E., Bates B., and Schramm L. (1997) The elementalcomposition of stony cosmic spherules. Meteoritics & Planet.Sci., 32, 157–175.

Burnett D. S., Woolum D. S., Benjamin T. M., Rogers P. X. Z.,Duffy C. J., and Maggiore C. (1989) A test of the smoothnessof the elemental abundances of carbonaceous chondrites. Geo-chim. Cosmochim. Acta, 53, 471–481.

Buseck P. R. and Hua X. (1993) Matrices of carbonaceous chon-drite meteorites. Annu. Rev. Earth Planet. Sci., 21, 255–305.

Chyba C. F. and Sagan C. (1992) Endogenous production, exog-enous delivery and impact-shock synthesis of organic mole-cules: An inventory for the origins of life. Nature, 355, 125–132.

Ciesla F. J. and Hood L. L. (2002) The nebular shock wave modelfor chondrule formation: Shock processing in a particle-gassuspension. Icarus, 158, 281–293.

Clayton R. N. (2002) Self-shielding in the solar nebula. Nature,415, 860–861.

Clayton R. N. and Mayeda T. K. (1988) Formation of ureilites bynebular processes. Geochim. Cosmochim. Acta, 52, 1313–1318.

Clayton R. N. and Mayeda T. K. (1996) Oxygen isotope studiesof achondrites. Geochim. Cosmochim. Acta, 60, 1999–2017.

Cody G. D., Alexander C. M. O’D., and Tera F. (2002) Solid-state (1H and 13C) nuclear magnetic resonanance spectroscopyof insoluble organic residue in the Murchison meteorite: Aself-consistent quantitative analysis. Geochim. Cosmochim.Acta, 66, 1851–1865.

Connolly H. C., Hewins R. H., Ash R. D., Zanda B., LofgrenG. E., and Bourot-Denise M. (1994) Carbon and the forma-tion of reduced chondrules. Nature, 371, 136–139.

Cooper G. W., Thiemens M. H., Jackson T.-L., and Chang S.(1997) Sulfur and hydrogen isotope anomalies in meteoritesulfonic acids. Science, 277, 1072–1074.

Cronin J. R. and Pizzarello S. (1997) Enantiomeric excesses inmeteoritic amino acids. Science, 275, 951–955.

Cuzzi J. N., Dobrovolskis A. R., and Hogan R. C. (1996) Turbu-lence, chondrules, and planetesimals. In Chondrules and theProtoplanetary Disk (R. H. Hewins et al., eds.), pp. 35–43.Cambridge Univ., New York.

Desch S. J. and Connolly H. C. (2002) A model of the thermalprocessing of particles in solar nebula shocks: Application tothe cooling rates of chondrules. Meteoritics & Planet. Sci., 37,183–207.

Endress M., Zinner E., and Bischoff A. (1996) Early aqueousactivity on primitive meteorite parent bodies. Nature, 279, 701–703.

Engel M. H. and Macko S. A. (1997) Isotopic evidence for extra-


terrestrial non-racemic amino acids in the Murchison meteorite.Nature, 389, 265–268.

Farinella P., Vokrouhlický D., and Hartmann W. (1998) Meteor-ite delivery via Yarkovsky orbital drift. Icarus, 132, 378–387.

Flynn G. J., Keller L. P., Feser M., Wirick S., and Jacobsen C.(2003) The origin of organic matter in the solar system: Evi-dence from the interplanetary dust particles. Geochim. Cosmo-chim. Acta, 67, 4791–4806.

Gilmour I. (2003) Structural and isotopic analysis of organicmatter in carbonaceous chondrites. In Treatise on Geochemis-try, Vol. 1: Meteorites, Comets, and Planets (A. M. Davis, ed.),pp. 269–290. Elsevier, Oxford.

Gilmour J. D., Whitby J. A., Turner G., Bridges J. C., andHutchison R. (2000) The iodine-xenon system in clasts andchondrules from ordinary chondrites: Implications for earlysolar system chronology. Meteoritics & Planet. Sci., 35, 445–455.

Gladman B. J., Migliorini F., Morbidelli A., Zappala V., MichelP., Cellino A., Froeschle C., Levinson H. F., Bailey M., andDuncan M. (1997) Dynamical lifetimes of objects injected intoasteroid belt resonances. Science, 277, 197–201.

Goodrich C. A. (1992) Ureilites: A critical review. Meteoritics,27, 327–352.

Goodrich C. A. and Delaney J. S. (2000) Fe/Mg-Fe/Mn relationsof meteorites and primary heterogeneity of primitive achon-drite parent bodies. Geochim. Cosmochim. Acta, 64, 149–160.

Göpel C., Manhes G., and Allègre C. J. (1994) U-Pb systematicsof phosphates from equilibrated ordinary chondrites. EarthPlanet. Sci. Lett., 121, 153–171.

Gounelle M. and Zolensky M. E. (2001) A terrestrial origin forsulfate veins in CI1 chondrites. Meteoritics & Planet. Sci., 36,1321–1329.

Gounelle M., Shu f. H., Shang H., Glassgold A. E., Rehm K. E.,and Lee T. (2001) Extinct radioactivities and protosolar cos-mic rays: Self-shielding and light elements. Astrophys. J., 548,1051–1070.

Greenwood R. C., Kearsley A. T., and Franchi I. A. (2003) AreCK chondrites really a distinct group or just equilibrated CVs?(abstract). Meteoritics & Planet. Sci., 38, A96.

Greshake A., Klock W., Arndt P., Maetz M., Flynn G. J., Bajt S.,and Bischoff A. (1998) Heating experiments simulating atmo-spheric entry heating of micrometeorites: Clues to their par-ent body sources. Meteoritics & Planet. Sci., 33, 267–290.

Grossman J. N., Rubin A. E., and MacPherson G. J. (1988) ALH85085: A unique volatile-poor carbonaceous chondrite withpossible implications for nebular fractionation processes. EarthPlanet. Sci. Lett., 91, 33–54.

Grossman L., Ebel D. S., and Simon S. B. (2002) Formation ofrefractory inclusions by evaporation of condensate precursors.Geochim. Cosmochim. Acta, 66, 145–161.

Haack H. and McCoy T. J. (2003) Iron and stony-iron meteorites.In Treatise on Geochemistry, Vol. 1: Meteorites, Comets, andPlanets (A. M. Davis, ed.), pp. 325–345. Elsevier, Oxford.

Herzog G. F. (2003) Cosmic-ray exposure ages of meteorites. InTreatise on Geochemistry, Vol. 1: Meteorites, Comets, andPlanets (A. M. Davis, ed.), pp. 347–380. Elsevier, Oxford.

Hewins R. H. (1997) Chondrules. Annu. Rev. Earth Planet. Sci.,25, 61–83.

Hewins R. H., Jones R. H., and Scott E. R. D., eds. (1996) Chon-drules and the Protoplanetary Disk. Cambridge Univ., NewYork.

Hopfe W. D. and Goldstein J. I. (2001) The metallographic cool-

ing rate method revised: Application to iron meteorites andmesosiderites. Meteoritics & Planet. Sci., 36, 135–154.

Hoppe P. and Zinner E. (2000) Presolar dust grains from meteor-ites and their stellar sources. J. Geophys. Res., 105, 10371–10385.

Humayun M. and Clayton R. N. (1995) Potassium isotope cosmo-chemistry: Genetic implications of volatile element depletion.Geochim. Cosmochim. Acta, 59, 2131–2148.

Humayun M. and Campbell A. J. (2002) The duration of ordinarychondrite metamorphism inferred from tungsten microdistribu-tion in metal. Earth Planet. Sci. Lett., 198, 225–243.

Huss G. R. (1990) Ubiquitous interstellar diamond and SiC inprimitive chondrites: Abundances reflect metamorphism. Na-ture, 347, 159–162.

Huss G. R. and Lewis R. S. (1995) Presolar diamond, SiC, andgraphite in primitive chondrites: Abundances as a function ofmeteorite class and petrologic type. Geochim. Cosmochim.Acta, 59, 115–160.

Ireland T. R. and Fegley B. Jr. (2000) The solar system’s earliestchemistry: Systematics of refractory inclusions. Intern. Geol.Rev., 42, 865–894.

Kallemeyn G. W., Rubin A. E., and Wasson J. T. (1991) The com-positional classification of chondrites: V. The Karoonda (CK)group of carbonaceous chondrites. Geochim. Cosmochim. Acta,55, 881–892.

Kallemeyn G. W., Rubin A. E., and Wasson J. T. (1996) The com-positional classification of chondrites: VII. The R chondritegroup. Geochim. Cosmochim. Acta, 60, 2243–2256.

Kehm K., Flynn G. J., Sutton S. R., and Hohenberg C. M. (2002)Combined noble gas and trace element measurements on indi-vidual stratospheric interplanetary dust particles. Meteoritics& Planet. Sci., 37, 1323–1335.

Kerridge J. F. and Matthews M. S., eds. (1988) Meteorites andthe Early Solar System. Univ. of Arizona, Tucson. 1268 pp.

Keller L. P., Messenger S., Flynn G. J., Clemett S., Wirick S.,and Jacobsen C. (2004) The nature of molecular cloud mate-rial in interplanetary dust. Geochim. Cosmochim. Acta, 68,2577–2589.

Kimura M., Hiyagon H., Palme H., Spettel B., Wolf D., ClaytonR. N., Mayeda T. K., Sato T., Suzuki T., and Kojima H. (2002)Anomalous H-chondrites, Y792947, Y93408 and Y82038, withabundant refractory inclusions and very low metamorphicgrade. Meteoritics & Planet. Sci., 37, 1417–1434.

Kita N. T., Nagahara H., Togashi S., and Morishita T. (2000) Ashort duration of chondrule formation in the solar nebula:Evidence from 26Al in Semarkona ferromagnesian chondrules.Geochim. Cosmochim. Acta, 64, 3913–3922.

Kita N. T., Ikeda Y., Togashi S., Liu Y., Morishita Y., and WeisbergM. K. (2004) Origin of ureilites inferred from a SIMS oxygenisotopic and trace element study of clasts in the Dar al Gani319 polymict ureilite. Geochim. Cosmochim. Acta, 68, 4213–4235.

Kleine T., Munker C., Mezger K., and Palme H. (2002) Rapidaccretion and early core formation on asteroids and the terres-trial planets from Hf-W chronometry. Nature, 418, 952–955.

Krot A. N., Scott E. R. D., and Zolensky M. E. (1995) Mineral-ogical and chemical modification of components in CV3 chon-drites: Nebular or asteroidal processing? Meteoritics, 30, 748–775.

Krot A. N., Meibom A., Weisberg M. K., and Keil K. (2002a) TheCR chondrite clan: Implications for early solar system pro-cesses. Meteoritics & Planet Sci., 37, 1451–1490.


Krot A. N., McKeegan K. D., Leshin L. A., MacPherson G. J.,and Scott E. R. D. (2002b) Existence of a 16O-rich gaseousreservoir in the solar nebula. Science, 295, 1051–1054.

Kuebler K. E., McSween H. Y., Carlson W. D., and Hirsch D.(1999) Sizes and masses of chondrules and metal-troilite grainsin ordinary chondrites: Possible implications for nebular sort-ing. Icarus, 141, 96–106.

Lauretta D. S., Lodders K., and Fegley B. (1997) Experimentalsimulations of sulfide-formation in the solar nebula. Science,277, 358–360.

Lee D.-C. and Halliday A. N. (1997) Hf-W isotopic evidence forrapid accretion and differentiation in the early solar system.Science, 274, 1876–1879.

Lewis, R. S., Amari S., and Anders E. (1990) Meteoritic siliconcarbide: Pristine material from carbon stars. Nature, 348, 293–298.

Lodders K. (2003) Solar system abundances and condensationtemperatures of the elements. Astrophys. J., 591(2), 1220–1247.

Lugmair G. W. and Shukolyukov A. (2001) Early solar systemevents and timescales. Meteoritics & Planet. Sci., 36, 1017–1026.

MacPherson G. J. (2003) Calcium-aluminum-rich inclusions inchondritic meteorites. In Treatise on Geochemistry, Vol. 1:Meteorites, Comets, and Planets (A. M. Davis, ed.), pp. 201–246. Elsevier, Oxford.

MacPherson G. J., Davis A. M., and Zinner E. K. (1995) Thedistribution of Al-26 in the early solar system — a reappraisal.Meteoritics, 30, 365–386.

MacPherson G. J., Huss G. R., and Davis A. M. (2003) Extinct10Be in type A calcium-aluminum-rich inclusions from CVchondrites. Geochim. Cosmochim. Acta, 67, 3165–3179.

Marhas K. K., Goswami J. N., and Davis A. M. (2002) Short-livednuclides in hibonite grains from Murchison: Evidence for solarsystem evolution. Science, 298, 2182–2184.

McCoy T. J., Keil K., Clayton R. N., Mayeda T. K., Bogard D. D.,Garrison D. H., Huss G. R., Hutcheon I. D., and Wieler R.(1996) A petrologic, chemical, and isotopic study of Monu-ment Draw and comparison with other acapulcoites: Evidencefor formation by incipient partial melting. Geochim. Cosmo-chim. Acta, 60, 2681–2708.

McCoy T. J., Keil K., Clayton R. N., Mayeda T. K., Bogard D. D.,Garrison D. H., and Wieler R. (1997) A petrologic study oflodranites: Evidence for early formation as partial melt resi-dues from heterogeneous precursors. Geochim. Cosmochim.Acta, 61, 623–637.

McKay D. S., Gibson E. K., Thomas-Keprta K. L., Vali H.,Romanek C. S., Clemett S. J., Chelier X. D. F., MaechlingC. R., and Zare R. N. (1996) Search for past life on Mars: Pos-sible relic biogenic activity in Martian meteorite ALH84001.Science, 273, 924–930.

McKeegan K. D. and Davis A. (2004) Early solar system chro-nology. In Treatise on Geochemistry, Vol. 1: Meteorites, Com-ets, and Planets (A. M. Davis, ed.), pp. 431–460. Elsevier,Oxford.

McKeegan K. D., Chaussidon M., and Robert F. (2000) Incorpora-tion of short-lived 10Be in a calcium-aluminum-rich inclusionfrom the Allende meteorite. Science, 289, 1334–1337.

McSween H. Y. and Labotka T. C. (1993) Oxidation during meta-morphism of the ordinary chondrites. Geochim. Cosmochim.Acta, 57, 1105–1114.

McSween H. Y., Ghosh A., Grimm R. E., Wilson L., and YoungE. D. (2002) Thermal evolution models of asteroids. In Aster-oids III (W. F. Bottke Jr. et al., eds.), pp. 559–571. Univ. ofArizona, Tucson.

Meibom A. and Clark B. E. (1999) Evidence for the insignificanceof ordinary chondritic material in the asteroid belt. Meteorit-ics & Planet. Sci., 34, 7–24.

Meibom A., Pataev M. I., Krot A. N., Wood J. A., and Keil K.(1999) Primitive FeNi metal grains in CH carbonaceous chon-drites formed by condensation from a gas of solar composi-tion. J. Geophys. Res., 104, 22053–22059.

Mendybaev R. A., Beckett J. R., Grossman L., Stolper E., Coo-per R. F., and Bradley J. P. (2002) Volatilization kinetics ofsilicon carbide in reducing gases: An experimental study withapplications to the survival of presolar grains in the solarnebula. Geochim. Cosmochim. Acta, 66, 661–682.

Messenger S. (2000) Identification of molecular-cloud material ininterplanetary dust particles. Nature, 404, 968–971.

Messenger S., Keller L. P., Stademann F. J., Walker R. M., andZinner E. (2003) Samples of stars beyond the solar system:Silicate grains in interplanetary dust. Science, 300, 105–108.

Metzler K., Bishoff A., and Stoffler D. (1992) Accretionary dustmantles in CM chondrites: Evidence for solar nebula pro-cesses. Geochim. Cosmochim. Acta, 56, 2873–2897.

Mittlefehldt D. W. (1994) ALH84001, a cumulate orthopyroxenitemember of the martian meteorite clan. Meteoritics, 29, 214–221.

Mittlefehldt D. W. (2002) Geochemistry of the ungrouped carbon-aceous chondrite Tagish Lake, the anomalous CM chondriteBells, and comparison with CI and CM chondrites. Meteorit-ics & Planet. Sci., 37, 703–712.

Mittlefehldt D. W. and Lindstrom M. M. (1990) Geochemistry andgenesis of the angrites. Geochim. Cosmochim. Acta, 54, 3209–3218.

Mittlehehldt D. W., McCoy T. J., Goodrich C. A., and KracherA. (1998) Non-chondritic meteorites from asteroidal bodies.In Planetary Materials (J. J. Papike, ed.), pp. 4-1 to 4-195.Reviews in Mineralogy, Vol. 36, Mineralogical Society ofAmerica.

Moustefaoui S., Kita N. T., Togashi S., Tachibana S., NagaharaH., and Morishita Y. (2002) The relative formation ages offerromagnesian chondrules inferred from their initial 26Al/27Al.Meteoritics & Planet. Sci., 37, 421–438.

Nakamura K., Zolensky M. E., Tomita S., Nakashima S., andTomeoka K. (2002) Hollow organic globules in the TagishLake meteorite as possible products of primitive organic reac-tions. Intern. J. Astrobiol., 1, 179–189.

Nehru C. E., Prinz M., Weisberg M. K. Ebihara M. E., ClaytonR. N., and Mayeda T. K. (1992) Brachintes: A new primitiveachondrite group (abstract). Meteoritics, 27, 267.

Nguyen A. and Zinner E. (2004) Discovery of ancient silicatestardust in a meteorite. Science, 303, 1496–1499.

Nier A. O. and Schlutter D. J. (1993) The thermal history of in-terplanetary dust particles collected in the Earth’s stratosphere.Meteoritics, 28, 675–681.

Nittler L. R. (2003) Presolar stardust in meteorites: Recent ad-vances and scientific frontiers. Earth Planet. Sci. Lett., 209,259–273.

Nittler L. R., Alexander C. M. O’D., Gao X., Walker R. M., andZinner E. (1997) Stellar sapphires: The properties and originsof presolar Al2O3 in meteorites. Astrophys. J., 483, 475–495.

Nyquist L. E., Bogard D. D., Shih C.-Y., Greshake A., StofflerD., and Eugster O. (2001) Ages and geologic histories of mar-tian meteorites. Space Sci. Rev., 96, 105–164.

Ott U. (1993) Interstellar grains in meteorites. Nature, 364, 25–33.Ott U. and Begemann F. (2000) Spallation recoil and age of

presolar grains in meteorites. Meteoritics & Planet. Sci., 35,53–63.


Palme H. (2001) Chemical and isotopic heterogeneity in protosolarmatter. Philos. Trans. R. Soc., 359, 2061–2075.

Palme H. and Jones A. (2003) Solar system abundances of theelements. In Treatise on Geochemistry, Vol. 1: Meteorites,Comets, and Planets (A. M. Davis, ed.), pp. 41–61. Elsevier,Oxford.

Pearson V. K., Sephton M. A., Kearsley A. T., Bland P. A., FranchiI. A., and Gilmour I. (2002) Clay mineral — organic matterrelationships in the early solar system. Meteoritics & Planet.Sci., 37, 1829–1833.

Pizzarello S., Huang Y., Becker L., Roreda R. J., Nieman R. A.,Cooper G., and Williams M. (2001) The organic content ofthe Tagish Lake meteorite. Science, 293, 2236–2239.

Richter K. and Drake M. J. (1997) A magma ocean on Vesta: Coreformation and petrogenesis of eucrites and diogenites. Mete-oritics & Planet. Sci., 32, 929–944.

Rietmeijer F. J. M. (1998) Interplanetary dust particles. In Plane-tary Materials (J. J. Papike, ed.), pp. 2-1 to 2-95. Reviews inMineralogy, Vol. 36, Mineralogical Society of America.

Rubin A. E. and Kallemeyn G. W. (1994) Pecora Escarpment91002: A member of the new Rumuruti (R) chondrite group.Meteoritics, 29, 255–264.

Rubin A. E. and Krot A. N. (1996) Multiple heating of chondrules.In Chondrules and the Protoplanetary Disk (R. H. Hewins etal., eds.), pp. 173–180. Cambridge Univ., New York.

Rubin A. E., Keil K., and Scott E. R. D. (1997) Shock metamor-phism of enstatite chondrites. Geochim. Cosmochim. Acta, 61,847–858.

Rubin A. E., Kallemeyn G. W., Wasson J. T., Clayton R. N.,Mayeda T. K., Grady M., Verchovsky A. B., Eugster O., andLorenzetti S. (2003) Formation of metal and silicate globulesin Gujba: A new Bencubbin-like meteorite fall. Geochim. Cos-mochim. Acta, 67, 3283–3298.

Russell S. S., Srinivasan G., Huss G. R., Wasserburg G. J., andMacPherson G. J. (1996) Evidence for widespread 26Al in thesolar nebula and constraints for nebula time scales. Science,273, 757–762.

Russell S. S., Ott U., Alexander C. M., Zinner E. K., Arden J. W.,and Pillinger C. T. (1997) Presolar silicon carbide from theIndarch (EH4) meteorite: Comparison with silicon carbidepopulations from other meteorite classes. Meteoritics & Planet.Sci., 32, 719–732.

Ruzicka A., Snyder G. A., and Taylor L. A. (1997) Vesta as thehowardite, eucrite and diogenite parent body: Implications forthe size of a core and for large-scale differentiation. Meteorit-ics & Planet. Sci., 32, 825–840.

Schoenberg R., Kamber B. S., Collerson K. D., and Eugster O.(2002) New W-isotope evidence for rapid terrestrial accretionand very early core formation. Geochim. Cosmochim. Acta, 66,3151–3160.

Schulte M. and Shock E. (2004) Coupled organic synthesis andmineral alteration on meteorite parent bodies. Meteoritics &Planet. Sci., 39, 1577–1590.

Schulze H., Bischoff A., Palme H., Spettel B., Dreibus G., andOtto J. (1994) Mineralogy and chemistry of Rumuruti: Thefirst meteorite fall of the new Rumuruti group. Meteoritics, 29,275–286.

Scott E. R. D. (1988) A new kind of primitive achondrite, AllanHills 85085. Earth Planet. Sci. Lett., 91, 1–18.

Scott E. R. D., Keil K., and Stoffler E. (1992) Shock metamor-phism of carbonaceous chondrites. Geochim. Cosmochim. Acta,56, 4281–4293.

Sephton M. A., Pillinger C. T., and Gilmour I. (1998) δ13C of freeand macromolecular polyaromatic structures in the Murchison

meteorite. Geochim. Cosmochim. Acta, 62, 1821–1828.Sephton M. A., Pillinger C. T., and Gilmour I. (1999) Small-scale

hydrous pyrolysis of macromolecular material in meteorites.Planet. Space Sci., 47, 181–187.

Sephton M. A., Pillinger C. T., and Gilmour I. (2000) Aromaticmoieties in meteoritic macromolecular materials: Analysis byhydrous pyrolysis and δ13C of individual compounds. Geo-chim. Cosmochim. Acta, 64, 321–328.

Sephton M. A., Verchovsky A. B., Bland P. A., Gilmour I., GradyM. M., and Wright I. P. (2003) Investigating variations in car-bon and nitrogen isotopes in carbonaceous chondrites. Geo-chim. Cosmochim. Acta, 67, 2093–2108.

Shen J. J., Papanastassiou D. A., and Wasserburg G. J. (1996)Precise Re-Os determinations and systematics of iron meteor-ites. Geochim. Cosmochim. Acta, 60, 2887–2900.

Shu F. H., Shang H., and Lee T. (1996) Toward an astrophysicalmodel of chondrites. Science, 271, 1545–1552.

Shukolyukov A. and Lugmair G. W. (1993) Live iron-60 in theearly solar system. Science, 259, 1138–1142.

Simon S. B. and Grossman L. (2003) Petrography and mineralchemistry of the anhydrous component of the Tagish Lake car-bonaceous chondrite. Meteoritics & Planet. Sci., 38, 813–825.

Singletary S. J. and Grove T. L. (2003) Early petrologic processeson the ureilite parent body. Meteoritics & Planet. Sci., 38, 95–108.

Smoliar M. I., Walker R. J., and Morgan J. W. (1996) Re-Os agesof group IIA, IIIA, IVA, and IVB iron meteorites. Science, 271,1099–1102.

Srinivasan G., Ulyanov A. A., and Goswami J. N. (1994) 41Ca inthe early solar system. Astrophys. J. Lett., 431, L67–L70.

Srinivasan G., Goswami J. N., and Bhandari N. (1999) 26Al ineucrite Piplia Kalan: Plausible heat source and formation chro-nology. Science, 284, 1348–1350.

Steele A., Goddard D. T., Stapleton D., Toporski J. K. W., PetersV., Bassinger V., Sharples G., Wynn-Williams D. D., andMcKay D. S. (2000) Investigations into an unknown organismon the martian meteorite Allan Hills 84001. Meteoritics &Planet. Sci., 35, 237–241.

Stöffler D., Keil K., and Scott E. R. D. (1991) Shock metamor-phism of ordinary chondrites. Geochim. Cosmochim. Acta, 55,3845–3867.

Swindle T. D., Davis A. M., Hohenberg C. M., MacPherson G. J.,and Nyquist L. E. (1996) Formation times of chondrules andCa-Al-rich inclusions: Constraints from short-lived radionu-clides. In Chondrules and the Protoplanetary Disk (R. H.Hewins et al., eds.), pp. 77–86. Cambridge Univ., Cambridge.

Tachibana S. and Huss G. R. (2003) The initial abundance of 60Fein the solar system. Astrophys. J. Lett., 588, L41–L44.

Tang M. and Anders E. (1988) Interstellar silicon carbide: Howmuch older than the solar system? Astrophys. J. Lett., 335,L31–L34.

Taylor G. J. (1992) Core formation in asteroids. J. Geophys. Res.,97, 14717–14726.

Theimens M. H. (1996) Mass-independent isotopic effects inchondrites: The role of chemical processes. In Chondrules andthe Protoplanetary Disk (R. H. Hewins et al., eds.), pp. 107–118. Cambridge Univ., Cambridge.

Trieloff M., Jessberger E. K., Herrwerth I., Hopp J., Fleni C.,Ghells M. Bourot-Denise M., and Pellas P. (2003) Structureand thermal history of the H-chondrite parent asteroid revealedby thermochronometry. Nature, 422, 502–506.

Walker D. and Grove T. (1993) Ureilite smelting. Meteoritics, 28,629–636.

Walker R. J., Horan M. F., Morgan J. W., Becker H., Grossman


J. N., and Rubin A. E. (2002) Comparative 187Re-187Os sys-tematics of chondrites: Implications regarding early solar sys-tem processes. Geochim. Cosmochim. Acta, 66, 4187–4201.

Weisberg M. K., Prinz M., Clayton R. N., and Mayeda T. K.(1993) The CR (Rennazo-type) carbonaceous chondrite groupand its implications. Geochim. Cosmochim. Acta, 57, 1567–1586.

Weisberg M. K., Prinz M., Clayton R. N., and Mayeda T. K.(2001) A new metal-rich chondrite grouplet. Meteoritics &Planet. Sci., 36, 401–418.

Weyer S., Munker C., and Mezger K. (2003) Nb/Ta, Zr/Hf andREE in the depleted mantle: Implications for the differentia-tion history of the crust-mantle system. Earth Planet. Sci. Lett.,205, 309–324.

Whitby J., Burgess R., Turner G., Gilmour J., and Bridges J.(2000) Extinct 129I in halite from a primitive meteorite: Evi-dence for evaporite formation in the early solar system. Sci-ence, 288, 1819–1821.

Wieler R. and Graf T. (2001) Cosmic ray exposure history ofmeteorites. In Accretion of Extraterrestrial Material on Earthover Time (B. Peucker-Ehrenbrink. and B. Schmitz, eds.),pp. 221–240. Kluwer Academic/Plenum, New York.

Wieler R., Pedroni A., and Leya I. (2000) Cosmogenic neon inmineral separates from Kapoeta: No evidence for an irradia-tion of its parent body regolith by an early active Sun. Mete-oritics & Planet. Sci., 35, 251–257.

Wilson L. and Keil K. (1991) Consequences of explosive erup-tions on small bodies: The case of the missing basalts on theaubrite parent body. Earth Planet. Sci. Lett., 104, 505–512.

Woolum D. S. and Hohenberg C. (1993) Energetic particle en-vironment in the early solar system — extremely long pre-compaction meteoritic ages or an enhanced particle flux. InProtostars and Planets III (E. H. Levy and J. I. Lunine, eds.),pp. 903–919. Univ. of Arizona, Tucson.

Yamaguchi A., Clayton R. N., Mayeda T. K., Ebihara M., OuraY., Miura Y. N., Haramura H., Misawa K., Kojima H., andNagao K. (2002) A new source of basaltic meteorites inferredfrom Northwest Africa 011. Science, 296, 334–336.

Yang C.-W., Williams D. B., and Goldstein J. I. (1996) A revi-sion of the Fe-Ni phase diagram at low temperatures (<400°C).J. Phase Equilibria, 17, 522–531.

Yang C.-W., Williams D. B. and Goldstein J. I. (1997) Low-tem-perature phase decomposition in metal from iron, stony-ironand stony meteorites. Geochim. Cosmochim. Acta, 61, 2943–2956.

Yin Q., Jacobsen S. B., Yamashita K., Blichert-Toft J., Telouk P.,and Albarede F. (2002) A short timescale for terrestrial planetformation from Hf-W chronometry of meteorites. Nature, 418,949–952.

Young E. D. (2000) Assessing the implications of K isotope cos-mochemistry for evaporation in the preplanetary solar nebula.Earth Planet. Sci. Lett., 183, 321–333.

Young E. D. and Russell S. S. (1998) Oxygen reservoirs in theearly solar nebula inferred from Allende CAI. Science, 282,452–455.

Yu Y. and Hewins R. H. (1998) Transient heating and chondruleformation: Evidence from sodium loss in flash heating simu-lation experiments. Geochim. Cosmochim. Acta, 62, 159–172.

Zanda B., Bourot-Denise M., Perron C., and Hewins R. H. (1994)Origin and metamorphic redistribution of silicon, chromium,and phosphorus in the metal of chondrites. Science, 265, 1846–1849.

Zinner E. (1998) Stellar nucleosynthesis and the isotopic compo-sition of presolar grains from primitive meteorites. Annu. Rev.Earth Planet. Sci., 26, 147–188.

Zolensky M. E., Bodnar R. J., Gibson E. K., Nyquist L. E., ReeseY., Shih C.-Y., and Wiesmann H. (1999) Asteroidal waterwithin fluid-inclusion-bearing halite in an H5 chondrite, Mona-hans. Science, 285, 1377–1379.

Zolensky M. E., Nakamura K., Gounelle M., Mikouchi T., KasamaT., Tachikawa O., and Tonui E. (2002) Mineralogy of TagishLake: An ungrouped type 2 carbonaceous chondrite. Meteor-itics & Planet. Sci., 27, 737–761.

Recent Advances in Meteoritics and Cosmochemistry · McSween et al.: Recent Advances in Meteoritics...

Documents

Transcript of Recent Advances in Meteoritics and Cosmochemistry · McSween et al.: Recent Advances in Meteoritics...