Allende Meteorite Research Articles

Oxygen isotopic distribution in an amoeboid olivine aggregate from the Allende CV chondrite: Primary and secondary processes

The oxygen isotopic distribution in an amoeboid olivine aggregate (AOA), TTA1-02, from the Allende CV3 chondrite has been determined by secondary ion mass spectrometry. The irregular shaped TTA1- 02 (5×3mm) consists mostly of olivine grains of ca. 5μm in diameter. Olivine grains of Mg-rich (Fo 95) and Fe-rich (Fo 60) composition are in direct contact with each other, with a sharp compositional boundary. Oxygen isotopic compositions of Fe-rich olivine grains are 16O-poor (Δ 17O ≅ −5‰), whereas Mg-rich olivine is 16O-rich (Δ 17O ≅ −25‰). Several Al-rich inclusions (<ca. 500 μm in diameter) are enclosed by olivine grains in the AOA. Oxygen isotopic compositions of spinel and fassaite in Al-rich inclusions are 16O-rich (Δ 17O ≅ −20‰), whereas those of anorthite, nepheline and phyllosilicate are 16O-poor (Δ 17O ≅ −5‰). We propose the following sequence of events during the formation of AOAs in the Allende meteorite: 1) Formation of Al-rich inclusions with 16O-rich oxygen isotopic composition; 2) Accretion of Mg-rich olivine grains with 16O-rich oxygen isotopic composition around Al-rich inclusions; 3) Accretion into parent body; and 4) Aqueous alteration in the parent body, which led to crystallization of 16O-poor minerals, Fe-rich olivine, anorthite, nepheline, and phyllosilicate. This is reflecting reactions among primary 16O-rich AOA minerals and aqueous fluid having 16O-poor oxygen isotopic composition. Fe-rich olivine grains precipitated from aqueous fluids, which partially dissolved pre-existing Mg-rich olivine grains. Sintering and Mg-Fe diffusion occurred during thermal metamorphism. Anorthite, nepheline and phyllosilicate in Al-rich inclusions replaced primary anorthite or melilite during the aqueous alteration stage.

Oral histories in meteoritics and planetary science: V. Brian Mason

Abstract— In this interview, Brian Mason describes the sudden awakening of his interest in meteorites during his student days at Canterbury College in New Zealand when he read a paper on the cosmic abundances of the elements by Victor M. Goldschmidt. Subsequently, he won a scholarship for graduate study abroad and wrote to Goldschmidt asking if he could do a thesis with him in Norway. Shortly after he began his research in Oslo, he fled the city, ahead of the German invasion of Norway, and completed his doctorate in Stockholm with a thesis on the iron‐manganese minerals of the Långban Mine. After the war he taught for 3 years at Canterbury College where he gave courses on mineralogy and geology (into which he inserted lectures on geochemistry) and led students in extensive field studies. In 1947, Mason accepted a professorship of mineralogy at Indiana University. While there, he wrote the landmark book, Principles of Geochemistry, which appeared in 1952. The following year he moved to New York City where he served as the Curator of Minerals at the American Museum of Natural History and an adjunct professor at Columbia University. He became fascinated with the museum's meteorite collection and discussed meteorites in his lectures, which inspired some of his outstanding students to enter the field. During a sabbatical year he spent as a Fulbright Professor in Japan, he gave an advanced level seminar on meteorites and based his book, Meteorites, on his lecture notes. Mason developed a rapid method of optically classifying chondritic meteorites that he applied to major collections in many countries, thus enabling curators to replace uninformative labels such as “stone” or “chondrite” with species names, and to recognize which of their meteorites were rare types demanding serious study. In 1965 he moved to the Smithsonian Institution in Washington, D.C. where he remained for the rest of his career. Early in 1968, he collected specimens from the spectacular fall of the Allende meteorite in Mexico, which proved to be a carbonaceous chondrite containing rare types of inclusions enriched in calcium and aluminum. His analyses showed how these inclusions could be divided into groups on the basis of their differing rare earth element patterns. Mason's studies of Allende continued while he investigated lunar samples returned by the Apollo missions and coauthored a book on them. Beginning in the latter 1970s, he applied his rapid classification of stony meteorites to the large numbers of specimens collected each year by U.S. teams on the Antarctic ice sheet. In 1992 he capped his career with a biography of Victor M. Goldschmidt. In recognition of his many fundamental contributions, The Meteoritical Society honored Brian Mason with its Leonard Medal at its meeting in 1972 at the University of Chicago.

Microscopic search for the carrier phase Q of the trapped planetary noble gases in Allende, Leoville and Vigarano

Abstract— High‐resolution transmission electron microscopy micrographs of acid‐resistant residues of the Allende, Leoville, and Vigarano meteorites show a great variety of carbon structures: curved and frequently twisted and intertwined graphene sheets, abundant carbon black‐like particles, and hollow “sacs”. It is suggested that perhaps all of these are carriers for the planetary Q‐noble gases in these meteorites. Most of these materials are pyrocarbons that probably formed by the pyrolysis of hydrocarbons either in a gas phase, or on hot surfaces of minerals. An attempt was made to analyze for argon with particle‐induced x‐ray emission in 143 spots of grains of floating and suspended matter from freeze‐dry cycles of an Allende bulk sample in water, and floating “black balls” from sonication in water of samples from the Allende meteorite. The chemical compositions of these particles were obtained, but x‐ray signals at the wavelength of argon were obtained on only a few spots.

Diffusion kinetics of Fe 2+ and Mg in aluminous spinel : experimental determination and applications

The diffusion coefficients of Fe 2+ and Mg in aluminous spinel at ∼20 kb, 950 to 1325°C, and at 30 kb, 1125°C have been determined via diffusion couple experiments and numerical modeling of the induced diffusion profiles. The oxygen fugacity, fO 2, was constrained by graphite encapsulating materials. The retrieved self-diffusion coefficients of Fe 2+ and Mg at ∼20 kb, 950 to 1325°C, fit well the Arrhenian relation, D = D 0exp(−Q/RT), where Q is the activation energy, with D 0(Fe) = 1.8 (±2.8) × 10 −5, D 0(Mg) = 1.9 (±1.4) × 10 −5 cm 2/s, Q(Fe) = 198 ± 19, and Q(Mg) = 202 ± 8 kJ/mol. Comparison with the data at 30 kb suggests an activation volume of ∼5 cm 3/mol. From analysis of compositional zoning in natural olivine-spinel assemblages in ultramafic rocks, previous reports concluded that D(Fe-Mg) in spinel with Cr/(Cr + Al) ≤0.5 is ∼10 times that in olivine. The diffusion data in spinel and olivine have been applied to the problems of preservation of Mg isotopic inhomogeneity in spinel within the plagioclase–olivine inclusions in Allende meteorite and cooling rates of terrestrial ultramafic rocks.

Planetary science. A new solar system basalt.

The year 1969 was exceptional for research on extraterrestrial samples. On 8 February, the Allende meteorite fell. The Ca, Al-rich inclusions in this meteorite are the oldest objects known to date, preserving the signatures of the primordial solar nebula from which the planets formed. Analysis of samples from this meteorite prepared laboratories worldwide for the study of lunar samples brought back to Earth in July of the same year. On 28 September 1969, the Murchison meteorite was observed to fall in Australia, providing the first convincing evidence of amino acids of extraterrestrial origin. Also in the same year, a Japanese expedition recovered nine dark rocks, later identified as meteorites, from the ice fields of Antarctica.

Laboratory Study of the Bidirectional Reflectance of Powdered Surfaces: On the Asymmetry Parameter of Asteroid Photometric Data

We performed laboratory experiments on the bidirectional reflectance of powdered surfaces of dunite, graphite, and Allende (CV3) and Gao (H5) meteorites. The particle size of each sample varied from tens to hundreds of micrometers. The absolute bidirectional reflectance was determined for two ranges of phase angle: from 2° to 80° at 0° angle of incidence and from 2° to 155° at 75° angle of incidence. The phase angle was incremented every 1° in between 2° and 5° and every 10° between 10° and 150°. We determined the Hapke parameters and found that the values of the asymmetry parameter retrieved for most of the samples were positive when the coverage of the phase angle was wide, 2° to 155°, although the values derived from remote sensing instruments on asteroid flyby missions have been negative or nearly zero. Among our sample surfaces, only those of graphite, Allende, and Gao with particle sizes of hundreds micrometers show negative or nearly zero values. The single-scattering albedos determined for the Gao samples are comparable to the values of S-class asteroids, while those for the Allende samples are much larger than those of C-class asteroids.

Planetary resources and astroecology. Planetary microcosm models of asteroid and meteorite interiors: electrolyte solutions and microbial growth--implications for space populations and panspermia.

Planetary microcosms were constructed using extracts from meteorites that simulate solutions in the pores of carbonaceous chondrites. The microcosms were found to support the growth of complex algal and microbial populations. Such astroecology experiments demonstrate how a diverse ecosystem could exist in fluids within asteroids, and in meteorites that land on aqueous planets. The microcosm solutions were obtained by extracting nutrient electrolytes under natural conditions from powders of the Allende (CV3) and Murchison (CM2) meteorites at low (0.02 g/ml) and high (10.0 g/ml) solid/solution ratios. The latter solutions contain > 3 mol/L electrolytes and about 10 g/L organics, that simulate natural fluids in asteroids during aqueous alteration and in the pores of meteorites, which can help prebiotic synthesis and the survival of early microorganisms. These solutions and wet solids were in fact found to support complex self-sustaining microbial communities with populations of 4 x 10(5) algae and 6 x 10(6) bacteria and fungi for long periods (> 8 months). The results show that planetary microcosms based on meteorites can: assay the fertilities of planetary materials; identify space bioresources; target astrobiology exploration; and model past and future space-based ecosystems. The results show that bioresources in the carbonaceous asteroids can sustain a biomass of 10(18) kg, comprising 10(32) microorganisms and a human population of 10(14). The results also suggest that protoplanetary nebulae can support and disperse microorganisms and can be therefore effective environments for natural and directed panspermia.

Mg isotope heterogeneity in the Allende meteorite measured by UV laser ablation-MC-ICPMS and comparisons with O isotopes

First results from a new UV laser ablation MC-ICPMS method for measuring Mg isotope ratios in situ in meteoritical materials show that there are mass-dependent variations in δ25Mg and δ26Mg up to 1.5 ‰ per amu in chondrules and 0.3‰ per amu in a CAI from the Allende meteorite. In both cases the mass-dependent fractionation is associated with alteration. Comparisons with laser ablation O isotope data indicate that incorporation of pre-existing grains of forsterite with distinct Mg and O isotopic compositions and post-formation alteration both contributed to the variability in Mg isotope ratios in the chondrules, resulting in a correlation between high δ25Mg and low Δ17O. The laser ablation analyses of the CAI show that high-precision determinations of both δ25Mg and δ26Mg can be used to discriminate features of the 26Al-26Mg isotope system that are relevant to chronology from those that result from element mobility.

Oxygen isotopic composition of a compound Ca-Al-rich inclusion from Allende meteorite: Implications for origin of palisade bodies and O-isotopic environment in the CAI forming region.

A calcium-aluminum-rich inclusion (CAI) containing big palisade bodies was found within the Allende meteorite. The bulk composition and mineral assemblages show that the CAI belongs to coarse-grained Type B. Oxygen isotopic distributions in palisade bodies in the CAI are similar to those observed in typical Type B CAIs, whereas all minerals including melilite in the host parts are enriched in 16O. The oxygen isotopic distribution in the CAI indicates that exchange of oxygen isotopes in the palisade bodies occurred before the trapping of palisades into the host. The palisade bodies were formed separately as small CAIs in the solar nebula and then accumulated together to form a large CAI. This suggests the possibility that during the CAI formation, O isotopic environment of CAI-forming region in the solar nebula repeatedly changed from 16O-rich to 16O-poor.

The Investigations of Chondritic Meteorites by X-ray Diffraction and Mössbauer Effect Methods

The Mossbauer spectroscopy and X-ray diffraction techniques were used to investigate the mineral and magnetic fractions of two meteorites: carbonaceous chondrite named Allende (CV3) and ordinary chondrite - El Hammami (H5). The investigations of a powder mixture of chondrules and matrix show that the meteorites studied contain iron mainly in the silicates, olivine, and pyroxene. The metallic fractions of the El Hammami meteorite contain the ferromagnetic mineral kamacite (bcc iron-nickel alloy). This phase with cubic symmetry was identified by symmetric Mossbauer spectrum with disturbance in relative line intensities. The results suggest that the Allende meteorite does not contain a pure metallic phase.

Isotope anomalies in tellurium and palladium from Allende nanodiamonds

Abstract— ‐The elemental and isotopic abundances of Te and Pd have been measured by thermal ionization mass spectrometry in a purified sample of interstellar nanodiamonds from the Allende meteorite, after combustion of the diamonds in an oxygen plasma. Small positive anomalies were found in 128Te (4.0 ± 1.5 %0) and 130Te (9.3 ± 2.8 %0) from three analyses of the Allende nanodiamond sample EB, and in 110Pd (9.4 ± 5.7 %0) from two analyses of the same sample. No other anomalies of a significant nature were found in either Te or Pd. These results are consistent with the neutron burst model (Meyer et al., 2000), and the r‐process based rapid separation model of Ott (1996) in that 128, 130Te and 110Pd are enhanced relative to their solar abundances. However, in the framework of the neutron burst model, some separation between stable products and radioactive precursors may be required in order to be consistent with the full data set of Te isotopes. In the framework of the rapid separation scenario, our data suggests a separation time of approximately 4000 s, based on the magnitudes of the precursor life‐times for 128Te and 130Te. The elemental abundance ratio Te‐H/Xe‐H agrees with the prediction of the rapid separation model, provided little fractionation occurred during trapping of the exotic components by the diamonds, but differs significantly from expectations based on the neutron burst model. Differences in the inferred 128Te/130Te ratio between our work and that of Richter et al. (1998) point to the need for further investigations.

Determination of total sulfur at microgram per gram levels in geological materials by oxidation of sulfur into sulfate with in situ generation of bromine using isotope dilution high-resolution ICPMS.

We have developed a new, simple, and accurate method for the determination of total sulfur at microgram per gram levels in milligram-sized silicate materials with isotope dilution high-resolution inductively coupled plasma mass spectrometry equipped with a flow injection system. In this method, sulfur can be quantitatively oxidized by bromine into sulfate with achievement of isotope equilibrium between the sample and spike. Detection limits for 32S+ and 34S+ in the ideal solution and silicate samples were 1 and 6 ng mL(-1) and 0.07 and 0.3 microg g(-1), respectively. The total blank was 46 ng, so that a 40-mg silicate sample containing 10 mirog g(-1) sulfur can be measured with a blank correction of < 10%. This total blank can be lowered to 8 ng if a low-blank air system is used for evaporations. To evaluate the applicability of this method, we analyzed not only silicate reference materials with sulfur content of 5.25-489 microg g(-1) and sample sizes of 13-40 mg but also the Allende meteorite with a sulfur content of 2%. The reproducibility for various rock types was < 9%, even though blank corrections in some samples of low sulfur content were up to 24%. This method is suitable for analyzing geological samples as well environmental samples such as soils, sediments, and water samples.

Extinct Radioactivities and Protosolar Cosmic Rays: Self‐Shielding and Light Elements

We study the effects of self-shielding in the X-wind model of protosolar cosmic-ray irradiation of early solar-system rocks. We adopt a two-component picture of protoCAIs consisting of cores with the elemental abundances of type B1 CAIs (calcium-aluminum-rich inclusions) and mantles of less refractory material. The cores have a power-law distribution of sizes between Rmin and Rmax. The mantles have a uniform thickness, whose value is chosen to bring the total inventory of elements at least as refractory as sulfur to cosmic abundances for the entire population of protoCAIs. Each object is irradiated with a fluence consistent with the product of their residence time in the reconnection ring and the flux of solar cosmic rays obtained by a scaling of impulsive flares from the hard X-rays observed from low-mass protostars. For Rmin in the 50 μm regime and Rmax in the few centimeter regime, which corresponds to the range of sizes of observed CAIs in micrometeorites and chondrites, we recover approximately the canonical values quoted for the ratios 26Al/27Al, 53Mn/55Mn, and 41Ca/40Ca in CV3 meteorites. Moreover, the excess 138La (denoted as 138La*) produced by proton bombardment of 138Ba lies within the CAI range obtained in the experiments of Shen et al. When we include fragmentation reactions that produce 10Be from the impact of protons, alphas, and 3He on the 16O that is bound up in rocks, we further obtain a level of 10Be/9Be that agrees approximately with the report of McKeegan et al. for a CAI from the Allende meteorite. Similar calculations for the expected anomalies in the stable isotopes of lithium show rough consistency with the measured values and further support our interpretation. The value for 10Be/9Be is particularly difficult to produce by any other astrophysical mechanism. Thus, the 10Be discovery greatly strengthens the case for an origin in early solar-system irradiation, rather than external stellar seeding, for the shortest-lived radionuclides inferred from CAIs in chondritic meteorites.

Earliest organic evolution. Essay to the memory of Bartholomew Nagy

A review is presented of the currently available evidence of life in the Precambrian, with special reference to microfossils of the size range 0.1–3 μm. The particles are spotted in thin sections of the rock under high apertures of the light microscope, and have been examined in demineralized thick sections under the transmission electron microscope (TEM). They have been chemically analyzed utilizing microprobe and spectrophotometer microscopic techniques. On the basis of such studies, the interaction of microorganisms with the formation of minerals can be traced back to early Archean times, 3800 million years ago. There is no indication supporting the assumption that some kind of prebiotic evolution took place in the recorded history of the Earth. The origin of life is open to alternative explanations, including extraterrestrial phenomena. More information may be obtained from meteorites. Under high magnifications of the TEM, a portion of the carbonaceous matter in the Murchison, Orgueil and Allende meteorites appears to be structured. Particles of various morphology can be distinguished. Microprobe techniques are applied to confirm that the microstructures are organic and indigenous to the rock. Possible origins by self-assembly and morphogenesis are discussed.

Application of multidimensional spectrum analysis for neutron activation analysis

Feasibility of the method of multidimensional γ-ray spectrometer for neutron activation analysis was examined. Reference igneous rock (JP-1, JB-1a and JB-1) samples issued by the Geological Survey of Japan (GSJ) and the Allende meteorite reference sample were irradiated in a research reactor, and multiple γ-rays from the produced radioisotopes via neutron capture reactions were measured using an array of twelve germanium detectors with BGO Compton suppressors called GEMINI. Simultaneously thirty elements were observed with no chemical separation. The observed smallest component was Eu contained in JP-1 with abundance of 4 ppb.

196Hg/202Hg ratio and Hg content in meteorites and terrestrial standard rocks: A RNAA study.

Radiochemical neutron activation was applied for the determination of mercury isotopic ratios (196Hg/202Hg) for standard rock samples and meteorite samples. After neutron activation, Hg was released upon heating from 100°C to 500°C at 100°C steps and the activity ratio of 197Hg/203Hg was measured for each released fraction. After the correction for the interfering γ-rays of 75Se to 203Hg, the ratios obtained from the Dhajala meteorite (bulk and magnetically separated samples) were identical to those of the Hg monitor as well as standard rock samples (JB-1, basalt, and JG-1, granodiorite). An apparently low ratio of 196Hg/202Hg was observed at high temperature (500°C) for the Allende meteorite reference sample. As such a low value was not reproduced in another run, the presence of isotopically anomalous Hg in the Allende reference sample can not be concluded. Hg/Se ratio was observed to be very high in the nonmagnetic fraction of Dhajala compared with that in the magnetic fraction, suggesting that Hg is less chalcophile than Se. Yamato 82050 (CO3) has an anomalously high content of Hg with a normal 196Hg/202Hg ratio, being at least an order of magnitude higher than the expected value. This meteorite must have been contaminated with Hg, presumably on Antarctica.

Fullerene-like carbon nanostructures in the Allende meteorite

Transmission electron microscopy has been used to examine carbon isolated from the Allende meteorite. The structure of the carbon is rather disordered, consisting of curved and faceted graphene sheets with little large scale graphitization, and resembles that of a microporous carbon following high temperature heat treatment. Closed carbon nanoparticles, typically ∼2–10 nm in diameter are commonly observed. These closed particles, which are probably fullerene-like in structure, are strong candidates to be carriers of planetary gases.

92Nb-(92)Zr and the Early Differentiation History of Planetary Bodies.

The niobium-92-zirconium-92 ((92)Nb-(92)Zr) extinct radioactive decay system (half-life of about 36 million years) can place new time constraints on early differentiation processes in the silicate portion of planets and meteorites. Zirconium isotope data show that Earth and the oldest lunar crust have the same relative abundances of (92)Zr as chondrites. (92)Zr deficits in calcium-aluminum-rich inclusions from the Allende meteorite constrain the minimum value for the initial (92)Nb/(93)Nb ratio of the solar system to 0.001. The absence of (92)Zr anomalies in terrestrial and lunar samples indicates that large silicate reservoirs on Earth and the moon (such as a magma ocean residue, a depleted mantle, or a crust) formed more than 50 million years after the oldest meteorites formed.

K, Mg, Ti and Ca isotopic compositions and refractory trace element abundances in hibonites from CM and CV meteorites: implications for early solar system processes

Potassium and magnesium isotopic compositions of hibonites from the Murchison (CM) and Allende (CV) meteorites are determined by an ion microprobe to look for possible presence of the short-lived nuclides 41Ca and 26Al at the time of their formation. Abundance anomalies in the neutron-rich isotopes 50Ti and 48Ca as well as REE and additional refractory trace element abundances have also been determined to infer a plausible formation environment of the hibonites in the early solar system. The results obtained in this study suggest a widespread distribution of the short-lived nuclide 41Ca in the early solar system. Observation of correlated presence of the two short-lived nuclides 41Ca and 26Al on a microscopic scale in refractory hibonites and silicates from CM and CV meteorites suggests these nuclides to be cogenetic and support a stellar source for these and several other short-lived nuclides in the early solar system. Moderate to high enrichments in the neutron-rich isotopes 50Ti and 48Ca are seen in some of the analyzed hibonites. Our data for radiogenic and stable isotopic anomalies as well as refractory trace element abundance patterns in isolated CM hibonites with platelet morphology show trends similar to those reported earlier. They are devoid of 41Ca and 26Al, show large enrichment in 50Ti and 48Ca and have typical Group III REE patterns. However, hibonites present within hibonite-spinel inclusions show variations in their REE patterns. One of them shows the normally expected Group II REE pattern, while another has an ultrarefractory REE pattern and a third has affinities towards platelet hibonites that appear to suggest a link between these two groups of hibonites with distinct morphological characteristics. We propose a new model to explain the absence of the short-lived nuclides 41Ca and 26Al in some of the hibonites, whose REE abundance patterns and stable isotopic anomalies suggest that they are some of the first solar system solids, assuming a stellar origin for these nuclides. We attribute this absence to the very early formation of these hibonites near the central region of the collapsing protosolar cloud prior to the arrival of the short-lived nuclides injected into the cloud from a stellar source.

Aspects of the validation of magnetic remanence in meteorites

Abstract— Meteorite magnetic records constitute physical evidence of processes acting during early solar system evolution. Consequently, the validation of these records is important in meteorite research. The first step in the validation process should be the REM value. The REM value is the ratio of natural remanence (NRM) to saturation remanent magnetization imparted by a 1 T magnetic field (SIRM). The REM values range over 3 to 4 orders of magnitude for stony meteorites and for chondrules from Allende (C3V‐S1), Bjurböle (L4‐S1), and Chainpur (LL3‐S1) meteorites.The REM values computed from published NRM and SIRM data identify many orders of magnitude range in the REM values including REM values &gt;100 × 10−3. These data suggest a dependence for the NRM intensity on the curatorial location from which the sample was obtained. Any earth rock acquiring thermoremanent magnetization (TRM) in the geomagnetic field has a restricted range in REM mostly between 5 and 50 × 10−3, the exception being the mineral hematite in the multidomain size range. The only terrestrial samples with REM much greater than 100 × 10−3 are those struck by lightning.The REM value provides a physical basis for recognition between valid records and those that “might be contaminated.” The isothermal remanence acquisition (RA) curve is presented as a contamination curve that allows an indication of the level of magnetic field contamination required to give the computed “REM” (RM/SIRM) value. In the case of the Bjurböle and Chainpur chondrules, with REM values &gt;100 × 10−3, the RA curve indicates that unrealistically large contamination magnetic fields would be required to give REM values greater than 100 × 10−3. This would suggest contamination other than by a hand magnet that is normally available to an experimenter. This would require an explanation that would involve large magnetic fields during chondrule formation, or some extraordinary remanence acquisition mechanism that remains to be described.Magnetic contamination experiments, using ∼80 and ∼40 mT magnets, demonstrate that the “REM” values and extent of modification of the magnetic vector record are mineralogy dependent, and this is mostly related to the amount and characteristics of the mineral tetrataenite. The complexity of the meteorite records suggest validation of the record as a first step. The REM value is the first physical statement that can be made in this validation.