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Z efektem Mössbauera na Marsie

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EN
People have been trying to send space vehicles to Mars since the early 1960s to explore the surface of this planet. One of the most important missions in discovering Mars was the Viking mission of 1975, which provided a lot of information shaping knowledge about the red planet at the turn of the century. The idea of sending Mössbauer spectrometer to Mars appeared due to the prevalence of iron in the planet's surfce and due to the specific properties of Mössbauer spectroscopy. Our paper describes the Warsaw project to send a Mössbauer spectrometer (MARMOS) to Mars and the project suggested by scientists from Mainz University (MIMOS II). A special Mössbauer spectrometer was constructed for the MER mission by West European Team. The paper presents the possibilities of using a miniaturized Mössbauer spectrometer for the investigation of archeological artefacts. The Mössbauer spectra obtained on the surface of Mars were discussed. The Mössbauer spectra obtained on the surface of Mars were discussed. The Mössbauer spectra measured on Mars are characterized by three doublets and one or two magnetic sextets. The spectra consist of a Fe3+ doublet (assigned to nanophase ferric oxide), two Fe2+ doublets (assigned to olivine and pyroxen) and two sextets (assigned to nonstoichiometric magnetite) or one sextet (assigned to a hematite-like phase).
EN
Mössbauer measurements of one sample of the Pułtusk meteorite were performed at room temperature (300 K) and at temperature of liquid nitrogen (80 K). Following mineralogical phases were identified in Mössbauer spectra: olivine, pyroxene, troilite, kamacite, taenite, and a doublet associated with ferric iron. The differences in the percentage of spectral areas obtained for all subspectra are very small. It means that in the range of these temperatures the Debye–Waller factor is the same for all mineralogical phases present in the investigated sample.
EN
Mössbauer spectra of equilibrated ordinary chondrites consist of two sextets due to magnetically ordered iron present in metallic phases and troilite and two doublets due to paramagnetic iron present in olivines and pyroxenes. The Mössbauer spectral areas of the different mineralogical phases in meteorites are proportional to the number of iron ions present in olivines, pyroxenes, metallic phase and troilite. This property of Mössbauer spectra was the basis for constructing various methods for the classification of ordinary chondrites. Review of these methods will be presented.
EN
The results of two independent Mössbauer measurements of the same sample of the Pultusk meteorite are discussed. The measurements were performed at room temperature in standard conditions (256 channels) and with higher resolution (1024 channels). Very small differences in the percentage of the spectral areas of all mineralogical phases present in Mössbauer spectrum (olivine, pyroxene, metallic phases, troilite and ferric iron) convince that the measurement performed at standard conditions (256 channels) are sufficient for correct determination of the mineralogical composition of the investigated sample.
EN
Four stony pieces were delivered to our laboratory for checking if they are fragments of meteorites: first sample (sample No. 1) was a fragment of a rock that fell near Leoncin in Poland, second sample (sample No. 2) was a fragment of a rock found also in Poland in the vicinity of Pultusk, third sample (sample No. 3) was a meteorite specimen bought on the meteorite exchange and fourth sample (sample No. 4) was a stone object whose decline was observed in Europe. We obtained mössbauer spectra of the delivered samples. The mössbauer spectrum of sample No. 1 is very similar to the spectrum of ordinary chondrite of type LL. Comparison of the mössbauer spectrum of sample No. 2 with mössbauer spectrum of Pułtusk meteorite showed very large differences. In the spectrum of sample No. 3, a clear signal from iron-nickel alloy and troilite can be observed. These observations indicate that it is an object of extraterrestrial origin. Mössbauer spectrum of Sample No. 4 is similar to the spectrum of terrestrial magmatic rocks. Based on these spectrum we cannot clearly determine where the examined object comes from. This work demonstrates the usefulness of Mössbauer spectroscopy in recognizing samples that are fragments of meteorites.
EN
Kuźnica meteorite was found in summer 2008 by an inhabitant of Częstochowa in the village of Kuźnica (Poland, voivodeship: Łódź, county: Pajęczano) in Poland. The finder, who is a passionate and collector of interesting stones, shared his find with the world only after a few years in the autumn of 2018. The found meteorite with a mass of 2.14 kg is an ordinary chondrite type H5. The degree of weathering on the surface is W2, inside W1. Currently, the meteorite is represented by 3 parts and two thin plates. The main mass is 2.037 kg, fragments are 13.7 g and 5.81 g. The found object was officially classified as a meteorite on 22th of November 2020. In this paper, we present the results of the Kuźnica meteorite measurements obtained by using the Mössbauer spectroscopy method. Mössbauer measurements of Kuźnica were performed at room temperature. The experimental spectrum was elaborated with “Recoil” program. Nine mineralogical phases were identified in the obtained Mössbauer spectrum: two doublets associated with olivine, two doublets associated with pyroxene, sextet associated with troilite, sextet associated with metallic phase identified as kamacite, doublet associated with iron hydroxides and two sextets associated with oxyhydroxides. The presence of a metallic phase or troilite in the test sample is convincing evidence of its extraterrestrial origin. These are mineralogical phases that can only arise in space conditions. Mössbauer spectroscopy allows for unambiguous identification of these mineralogical phases. In the standard 4M method, we use four basic phases to determine the type of ordinary chondrite: olivine, pyroxene, troilite and metallic phase, and we choose specimens in which the content of weathered phases does not exceed 7%. The Kuźnica meteorite is heavily weathered. The content of weathered phases is as much as 36.4%. Secondary minerals are a breakdown product of the metallic phase and to a lesser extent of the sulphide phase. Due to the strong weathering of the Kuźnica meteorite, we can modify the 4M method using only two basic phases: olivine and pyroxene. The analysis of the location of the Kuźnica meteorite on the figure of pyroxene vs. olivine dependence shows that it is ordinary chondrite type H. In this paper, the influence of the loss of the metallic and sulphide phases on the position of the Kuźnica meteorite on the figure of pyroxene/olivine vs. (pyroxene+metallic phase/(olivine+troilite)) was also checked. Weathering processes significantly transform many minerals. The resulting compounds often have parameters difficult to identify. However, difficulties in identifying secondary phases and their origins should not prevent an attempt to determine the type of meteorites using the 4M method.
EN
The 4M method aims to determine the type of equilibrated ordinary chondrite only on the basis of the Mössbauer spectrum of the investigated meteorite. Mössbauer spectrum of non-weathered ordinary chondrite is comprised of four sub-spectra: two doublets and two sextets. One of the doublets consists of a signal from iron present in olivine and the other consists of a signal from iron present in pyroxene. Sextets on the other hand, contain signals from magnetically ordered iron. One sextet is related to the metallic phase (kamacite, taenite), whereas the second is related to troilite. A third of doublets, which emerges in weathered ordinary chondrites, is related to products of the oxidation of iron present in metallic phase. The spectral areas of olivine, pyroxenes, metallic phase and troilite, which were obtained from Mössbauer spectrum are proportional to the number of iron atoms present in relevant mineral phases. Some Mössbauer groups were inspired by this fact to construct different methods to determine the type (H, L, or LL) of investigated meteorites (Gałązka-Friedman et al. 2019, Hyp. Inter. 241(1)). However, these methods, based on subjective criteria, were only qualitative. Our group elaborated a quantitative method, which is based on objective criteria. We called it the "4M method" (where M are derived from meteorites, Mössbauer spectroscopy, multidimensional discriminant analysis (MDA), Mahalanobis distance) (Woźniak et al. 2019). This method was using only the Mössbauer experimental data, to which it applied advanced statistical methods. The base, which was created from Mössbauer data, consisted of three clusters H, L, LL. These clusters were constructed with sets of 4-dimensional vectors. The vectors are comprised of spectral areas of Mössbauer spectrum: ol (value proportional to iron present in olivine), pyr (value proportional to iron present in pyroxene), met (value proportional to iron present in metallic phase), tr (value proportional to iron present in troilite). To determine the type of investigated ordinary chondrite, its ol, pyr, met and tr values with average values of variables obtained for clusters H, L and LL need to be compared. The comparison can be performed with the use of MDA and Mahalanobis distance. Once Mahalanobis distance of the investigated meteoriteis is known, the level of similarity to three types of ordinary chondrites can be calculated. Examples of such calculations were performed for seven ordinary chondrites: Goronyo, Carancas, New Concord, NWA 7733, Leoncin, Sołtmany and Pułtusk. They were made with the use of the new base composed of 62 non-weathered ordinary chondrites. All results obtained with the 4M method yielded results consistent with traditional mineralogical methods.
EN
Mössbauer 57Fe measurements of three ordinary chondrites type L were performed at room temperature. The measurements were repeated in the same experimental conditions. The experimental spectra were elaborated with „Recoil” program. The absorption areas of the same ordinary chondrite samples were very similar. The maximum variation was about 2% for doublets (paramagnetic iron) and 3% for sextet (magnetically ordered iron).
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