A key stage in planet formation is the evolution of a gaseous and magnetized solar nebula. However, the lifetime of the nebular magnetic field and nebula are poorly constrained. We present paleomagnetic analyses of volcanic angrites demonstrating that they formed in a near-zero magnetic field (<0.6 microtesla) at 4563.5 ± 0.1 million years ago, ~3.8 million years after solar system formation. This indicates that the solar nebula field, and likely the nebular gas, had dispersed by this time. This sets the time scale for formation of the gas giants and planet migration. Furthermore, it supports formation of chondrules after 4563.5 million years ago by non-nebular processes like planetesimal collisions. The core dynamo on the angrite parent body did not initiate until about 4 to 11 million years after solar system formation.

The Vicência meteorite, a stone of 1.547 kg, fell on September 21, 2013, at the village Borracha, near the city of Vicência, Pernambuco, Brazil. It was recovered immediately after the fall, and our consortium study showed it to be an unshocked (S1) LL3.2 ordinary chondrite. The LL group classification is based on the bulk density (3.13 g cm À3 ); the chondrule mean apparent diameter (0.9 mm); the bulk oxygen isotopic composition (d 17 O = 3.768 AE 0.042&, d 18 O = 5.359 AE 0.042&, D 17 O = 0.981 AE 0.020&); the content of metallic Fe,Ni (1.8 vol%); the Co content of kamacite (1.73 wt%); the bulk contents of the siderophile elements Ir and Co versus Au; and the ratios of metallic Fe 0 /total iron (0.105) versus total Fe/Mg (1.164), and of Ni/ Mg (0.057) versus total Fe/Mg. The petrologic type 3.2 classification is indicated by the beautifully developed chondritic texture, the standard deviation (~0.09) versus mean Cr 2 O 3 content (~0.14 wt%) of ferroan olivine, the TL sensitivity and the peak temperature and peak width at half maximum, the cathodoluminescence properties of chondrules, the content of trapped 132 Xe tr (0.317 9 10 À8 cm 3 STP g À1 ), and the Raman spectra for organic material in the matrix. The cosmic ray exposure age is~72 Ma, which is at the upper end of the age distribution of LL group chondrites. The meteorite is unusual in that it contains relatively large, up to nearly 100 lm in size, secondary fayalite grains, defined as olivine with Fa >75 , large enough to allow in situ measurement of oxygen and Mn-Cr isotope systematics with SIMS. Its oxygen isotopes plot along a mass-dependent fractionation line with a slope of~0.5 and D 17 O of 4.0 AE 0.3&, and are similar to those of secondary fayalite and magnetite in the unequilibrated chondrites EET 90161, MET 96503, and Ngawi. These data suggest that secondary fayalite in Vicência was in equilibrium with a fluid with a D 17 O of~4&, consistent with the composition of the fluid in equilibrium with secondary magnetite and fayalite in other unequilibrated ordinary chondrites. Secondary fayalite and the chondrule olivine phenocrysts in Vicência are not in isotopic equilibrium, consistent with low-temperature formation of fayalite during aqueous alteration on the LL parent body. That alteration, as dated by the 53 Mn-53 Cr chronology age of secondary fayalite, took place 4:0 þ1:4 À1:1 Ma after formation of CV CAIs when anchored to the quenched angrite D'Orbigny.

Resumo O meteorito Bendegó, uma massa de ferro e níquel com 5.360 kg, é o maior exemplar da coleção brasileira e detentor de uma rica história de contribuições à ciência meteorítica. Sua descoberta em 1784 no sertão da Bahia, sua épica remoção para o Museu Nacional (Rio de Janeiro) no final do século XIX e sua participação em estudos que estabeleceram a classificação química dos meteoritos metálicos na década de 1970 credenciam esse visitante espacial a reafirmar junto à comunidade geológica brasileira a importância dessas amostras extraterrestres que são autênticos arquivos repletos de informações sobre o que ocorreu nos primórdios do sistema solar e nos processos de diferenciação química dos planetas e asteróides. Este artigo estuda esse meteorito em seus contextos histórico, cósmico, geológico, petrológico e geoquímico lançando mão de técnicas analíticas avançadas a exemplo da análise por ativação de nêutrons, a espectroscopia de massa indutivamente acoplada a plasma e a microscopia eletrônica de varredura para melhor caracterizar as propriedades dessa massa de Fe-Ni que algum dia era parte integrante do núcleo de um objeto espacial suficientemente grande para experimentar um processo de diferenciação química.Palavras-Chave: Bendegó, meteorito, meteorítica, Bahia, ferro. Abstract The Bendego meteorite: history, mineralogy and chemical classification The Bendegómeteorite, an iron and nickel mass weighting 5,360 kg, is the largest specimen in the Brazilian collection and holds a rich record of contributions to the meteoritic science. Its finding in 1784 in the hinterland of Bahia State, its epic transportation to the National Museum (Museu Nacional, Rio de Janeiro) in the end of the XIX century, and its participation in the studies which lead to the chemical classification of the metallic meteorites in the 70´s, grant to this space visitor enough credibility to reinforce to the Brazilian geologic community the importance of those extraterrestrial samples, which are authentic records of the beginning of the solar system and early chemical differentiation processes of planets and asteroids. This paper presents new insights regarding the Bendegó historic, cosmic, geologic, petrologic and geochemical context and takes advantage from modern analytical methods, such as the instrumental neutron activation analysis, mass inductively coupled plasma spectroscopy, and scanning electronic microscopy, to better characterize the properties of such a Fe-Ni mass which, someday, would be the core of a space object, big enough to experiment a chemical differentiation process.

Abstract— The catalogue for the meteorite collection of Museu Nacional‐Universidade Federal do Rio de Janeiro, Brazil is presented. The collection contains 45 iron meteorites, 45 chondrites, 9 achondrites, and 5 stony‐iron meteorites. It houses 39 of the 50 Brazilian meteorites so far reported. The collection also includes some tektites, fulgurites, natural glasses, and some mislabeled meteorites not reported here.

Serra Pelada is the newest Brazilian eucrite and the first recovered fall from Amazonia (State of Pará, Brazil, June 29 th 2017). In this paper, we report on its petrography, chemistry, mineralogy and its magnetic properties. Study of four thin sections reveals that the meteorite is brecciated, containing basaltic and gabbroic clasts, as well of recrystallized impact melt, embedded into a fine-medium grained matrix. Chemical analyses suggest that Serra Pelada is a monomict basaltic eucritic breccia, and that the meteorite is a normal member of the HED suite. Our results provide additional geological and compositional information on the lithological diversity of its parent body. The mineralogy of Serra Pelada consists basically of low-Ca pyroxene and high-Ca plagioclase with accessory minerals such as quartz, sulphide (troilite), chromite -ulvöspinel and ilmenite. These data are consistent with the meteorite being an eucrite, a basaltic achondrite and a member of the howardite-eucrite-diogenite (HED) clan of meteorites which most likely are from the crust asteroid 4 Vesta.Key words: Serra Pelada, meteorite, eucrite, Vesta, Brazilian Meteorite.