Meteorites: messengers from the outer space

Abstract

Milhares de meteoróides, corpos sólidos do espaço extra-terrestre, entram na atmosfera da Terra a cada ano. São pedaços de rocha, metal ou aglomerados de rocha e metal, variando em massa de frações de grama a centenas de quilogramas. Aqueles que sobrevivem à passagem através da atmosfera e caem na Terra, são chamados meteoritos. Os meteoritos são as rochas primitivas, tão antigas quanto o Sistema Solar. O estudo desses objetos enigmáticos intriga os cientistas desde tempos antigos, não apenas por seu local de origem, mas também pelas condições que prevaleceram na sua formação, dando origem a estruturas e composições química e mineralógica características. Essas rochas primitivas são mensageiras do espaço extraterrestre que carregam consigo preciosos segredos sobre a formação do Sistema Solar, depende de nós revelá-los. Nesse artigo apresentamos uma revisão do trabalho realizado no Centro Brasileiro de Pesquisas Físicas (CBPF/MCT), aplicando a espectroscopia Mössbauer ao estudo do sistema Fe-Ni meteorítico.Tens of millions of meteoroids, solid bodies from the outer space, enter the Earth´s atmosphere each year. They are pieces of stone, iron or stony-iron conglomerates, ranging in mass from fractions of a gram to hundreds of kilograms. Those that survive the passage through the atmosphere and fall to Earth are called meteorites. Meteorites are the most ancient and primitive rocks as old as the Solar system. The study of these enigmatic objects intrigued scientists since ancient times, not only about their place of origin but also about the conditions that prevailed there and gave rise to their characteristic chemical and mineralogical composition and structures. These primitive rocks are messengers from the outer space that carry with them precious secrets about the formation of the Solar system, depends on us to reveal them. In this paper a review of the work done in the Centro Brasileiro de Pesquisas Físicas (CBPF/MCT), applying the Mössbauer spectroscopy to the study of the meteoritic Fe-Ni system will be reported.

Applications of Mössbauer Spectroscopy in Meteoritical and Planetary Science, Part I: Undifferentiated Meteorites

“…Now, we have about 60 years of experience in the applications of Mössbauer spectroscopy in the study of extraterrestrial materials (the first short reviews see in [9][10][11]). Then, some other reviews were published, for example, (i) concerning ideas of the solar system evolution analysis using Mössbauer spectroscopy data [12]; (ii) study of meteorites [13] and meteoritic Fe-Ni alloy [14,15]; (iii) studies of spinels in meteorites [16]; and (iv) Mössbauer spectroscopy of ordinary chondrites [17]. Further development of Mössbauer spectrometers led to appearance of new possibilities in its applications.…”

Kinetics of tetrataenite disordering

“…It is worth mentioning that a synthetic analog of tetrataenite can be prepared by a number of non-conventional methods (e.g., mechanical alloying, neutron/electron irradiation) which are known to enhance diffusion, thus allowing equilibrium to be reached in short times [9,11]. Nevertheless, comparison between the meteoritic tetrataenite and its synthetic analog produced by electron irradiation showed that in spite of similar composition, the ordering degree is much higher in meteoritic tetrataenite [13].…”

Fe–Ni Alloys at High Pressures and Temperatures: Statistical Thermodynamics and Kinetics of the $L1_{2}$ or $D0_{19}$ Atomic Order

“…Іншою характерною особливістю цих стопів є те, що вони є ме-теоритними (зокрема, бразильська авторка роботи [166] називає їх «посланцями» відкритого космосу), коли склад їх становить приблизно Fe-35 ат.% Ni [166]. Детально властивості (магне-тизм, коефіцієнт термічного розширення, параметер ґратниці, електричний опір, коефіцієнт взаємної дифузії та структурні ха-рактеристики) інварних стопів Fe-Ni було розглянуто в огляді Раccеля й Гарнера [337].…”

“…Також відомо, що впорядковані й невпорядковані фази Fe-Ni з інварними (й неінварними) концентраціями було виявлено в ме-теоритних стопах (див., наприклад, [166,[349][350][351][352][353][354][355][356][357][358]). Такі метео-ритні Fe-Ni-стопи з інварними концентраціями розпадаються на (не)впорядковану ГЦК-фазу Fe 3 Ni та впорядковану фазу типу L1 0 -FeNi [359].…”