Three meteorites -Bassikounou, Buzzard Coulee, and Zag -were studied with the use of the Mössbauer spectroscopy to assess how different experimental conditions, e.g. different statistics, velocity resolution and different ways of fitting the Mössbauer spectra could cause discrepancies regarding the percentages of spectral areas of main mineral phases (olivine, pyroxene, metallic phase and troilite) present in ordinary chondrites. The answer to this question is crucial for creation of a common database for a new method of classification of ordinary chondrites based on Mössbauer spectroscopy. Our results show that none of the above factors could significantly affect the percentage of spectral areas in the samples measured and the differences obtained with the use of those various methods of assessment were on the level of one percentage point. The final conclusion from this comparative study is that the results from different laboratories could be included to the same database.
Classification of the meteorites is very complex, but in general all meteorites can be divided into three groups: stony, iron and stony-iron. Ordinary chondrites are the most numerous group among stony meteorites. In this paper, we present short review of the methods of classification of ordinary chondrites. The classical method for the classification of ordinary chondrites is based on the determination of the content of fayalite in olivine and of the content of ferrosilite in pyroxene with the use of electron microprobe. This method was proposed in 1967. Studies on the application of Mössbauer spectroscopy to classification of ordinary chondrites were carried out since early 2000 in four Mössbauer laboratories. Mössbauer groups from Kanpur, Ekaterinburg and Canberra suggested qualitative methods of classification of ordinary chondrites. Warsaw group created quantitative method called the "4M method". This name derives from following words: meteorites, Mössbauer spectroscopy, multidimensional discriminant analysis, Mahalanobis distance. In this publication, we describe the use of 4M method for reclassification of meteorite Goronyo.
In our paper four Mӧssbauer spectra of ordinary chondrites (previously classified by a classical method based on determining the ratio of ferrosilite (Fs) to fayalite (Fa) with an electron microprobe) are presented and discussed. These are the Mӧssbauer spectra of two ordinary chondrites type H (Pultusk and Grzempach), one ordinary chondrite type L (Hyattville) and one type LL (NWA 6287). These meteorites were compared, using their Mӧssbauer spectra with the following four other samples: a fragment of a rock that fell near Leoncin in Poland (sample No. 1), a fragment of a rock found in the vicinity of Pultusk in Poland (sample No. 2), a meteorite specimen bought on the meteorite exchange (sample No. 3) and a stone object whose decline was observed in Europe (sample No. 4). The spectrum of sample No. 1 is very similar to the spectrum of ordinary chondrite of type LL. This observation was confirmed using 4M method (previously created by us). The spectrum of sample No. 2 differs significantly from the spectrum of sample of the Pultusk meteorite. In the spectrum of sample No. 3, a clear signal from iron-nickel alloy and troilite can be observed. This fact allows us to state that sample No. 3 is a fragment of rock that was created in cosmic conditions. Sample No. 4 has a Mӧssbauer spectrum similar to the spectrum of terrestrial magmatic rocks. This observation does not clearly determine where the examined object comes from. This work demonstrates the usefulness of Mӧssbauer spectroscopy in recognizing samples that are fragments of meteorites.
Abstract4M method is a new application of Mössbauer spectroscopy to quantitative classification of ordinary chondrites. 4M derives from four words: meteorites, Mössbauer spectroscopy, multidimensional discriminant analysis, Mahalanobis distance. This method was published by us in 2019. In this paper we present application of 4M method to classification of four meteorites. Link to script with calculation needed for classification of ordinary chondrites was given.
Space agencies are working on the project of capturing asteroids which contain natural resources valuable for industry. Based on studies of meteorites samples it was determined that the most useful source of raw materials for this purpose could be parent bodies of ordinary chondrites of type H. The identification of the type of ordinary chondrites with the use of a classical method (determination of the Fa/Fs ratio (fayalite versus ferrosilite) by electron microprobe measurements) cannot be performed on the surface of asteroids due to technical reasons. It may, however, be done based on Mössbauer measurements followed by the application of the 4M method. The name of the method – 4M, comes from four words: Meteorites, Mössbauer spectroscopy, Multidimensional discriminant analysis and Mahalanobis distance. Following the success of Mössbauer spectroscopy in the mission on Mars, there are suggestions to use the same method for the investigation of the surface of asteroids. In our experimental study, in which five Mössbauer laboratories took part, we assessed the effectiveness and reliability of the 4M method by comparison of the results obtained by Mössbauer studies of ordinary chondrites of type H, L and LL. Details of the study and problems related to the effectiveness of the 4M method are discussed.
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