Search

Carbonaceous chondrite meteorites are so far the only available samples representing carbon-rich asteroids and in order to allow future comparison with samples returned by missions such as Hayabusa 2 and OSIRIS-Rex, it is important to understand their physical properties. Future characterization of asteroid primitive classes, some of them targeted by sample-return missions, requires a better understanding of their mineralogy, the consequences of the exposure to space weathering, and how both affect the reflectance behaviour of these objects. In this paper, the reflectance spectra of two chemically related carbonaceous chondrites groups, precisely the Vigrano (CVs) and Karoonda (CKs), are measured and compared. The available sample suite includes polished sections exhibiting different petrologic types: from 3 (very low degree of thermal metamorphism) to 5 (high degree of thermal metamorphism). We found that the reflective properties and the comparison with the Cg asteroid reflectance class point towards a common chondritic reservoir from which the CV-CK asteroids collisionally evolved. In that scenario, the CV and CK chondrites could be originated from 221 Eos asteroid family, but because of its collisional disruption, both chondrite groups evolved separately, experiencing different stages of thermal metamorphism, annealing, and space weathering., This research has been funded by the research project (PGC2018-097374-B-I00, P.I.: JMT-R), funded by FEDER/Ministerio de Ciencia e Innovacion – Agencia Estatal de Investigación. ST is hired in the framework of that research project

Meteorites originating from primitive C-type asteroids are composed of materials from the Sun’s protoplanetary disk, including up to a few per cent organic carbon. In contrast, some interplanetary dust particles and micrometeorites have much higher carbon contents, up to >90%, and are thought to originate from icy outer Solar System bodies and comets. Here we report an approximately 100-µm-diameter very carbon-rich clast, with highly primitive characteristics, in the matrix of a CR2 chondrite, LaPaz Icefield 02342. The clast may represent a cometary building block, largely unsampled in meteorite collections, that was captured by a C-type asteroid during the early stages of planet formation. The existence of this cometary microxenolith supports the idea of a radially inward transport of materials from the outer protoplanetary disk into the CR chondrite reservoir during the formation of planetesimals. Moreover, the H-isotopic composition of the clast is suggestive of a temporal evolution of organic isotopic compositions in the comet-forming region of the disk. The composition and characteristics of a C-rich clast within the LaPaz Icefield 02342 meteorite suggests that the clast is composed of materials related to comets and icy bodies. The clast probably formed in the outer Solar System, was transported inward and finally accreted into LaPaz’s parent body.

Martian meteorites can provide valuable information about past environmental conditions on Mars. Allan Hills 84001 formed more than 4 Gyr ago, and owing to its age and long exposure to the Martian environment, and this meteorite has features that may record early processes. These features include a highly fractured texture, gases trapped during one or more impact events or during formation of the rock, and spherical Fe‐Mg‐Ca carbonates. In this study, we have concentrated on providing new insights into the context of these carbonates using a range of techniques to explore whether they record multiple precipitation and shock events. The petrographic features and compositional properties of these carbonates indicate that at least two pulses of Mg‐ and Fe‐rich solutions saturated the rock. Those two generations of carbonates can be distinguished by a very sharp change in compositions, from being rich in Mg and poor in Fe and Mn, to being poor in Mg and rich in Fe and Mn. Between these two generations of carbonate is evidence for fracturing and local corrosion., This research has been funded by the Spanish Ministry of Science and Innovation (projects: AYA2011‐26,522, AYA 2015‐67175‐P, CTQ2015‐62,635‐ERC, and CTQ2014‐60,119‐P to which J.M. Trigo‐Rodríguez and C.E. Moyano‐Cambero acknowledge financial support). The UK Science and Technology Facilities Council is also thanked for funding through grants ST/H002960/1, ST/K000942/1, and ST/L002167/1. ICN2 and ICMAB acknowledge support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grants SEV‐2013‐0295 and SEV‐2015‐0496, respectively.

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar-Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7–8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 ± 4 Ma. The results from short-lived radionuclides are compatible with an atmospheric pre-entry radius of 30–40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The 10Be concentration indicates a recent (3–5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30–35 cm pre-entry radius. © The Meteoritical Society, 2017.

Most asteroids of the near-Earth population have experienced significant collisional processing since they formed, being disrupted and excavated and consequently producing smaller bodies that are delivered from the Main asteroid Belt to the near-Earth asteroid region, thanks to planetary resonances and non-gravitational forces. By studying meteorites arrived to Earth we can obtain clues on this processing through the study of shock metamorphism and brecciation of their rock constituents, among other features. The massive Chelyabinsk meteorite fall produced about one metric ton of meteorites that can be analyzed to decipher the physical processes affecting the surface of this Potentially Hazardous Asteroid. Here we describe physical properties of Chelyabinsk samples, and how impact processing has affected asteroid albedos, a first step in order to relate this data with the reflectance properties of near-Earth asteroids population. This information will be of major interest for future asteroid deflecting missions.

Humanity has been mining Earth deposits for decades in order to extract tiny amounts of economically valuable metals and thereby, producing huge natural devastations of our planet. Recently, asteroids have grabbed our attention since they are fascinating objects carrying the hints of Solar System origin and, at the same time, containing large amounts of valuable resources including platinum group metals (Mining the sky: untold riches form the Asteroids, Comets, and Planets, Reading, 1996), iron, nickel, rare earth elements (REE), and water (Mining the sky: untold riches form the Asteroids, Comets, and Planets, Reading, 1996; The technical and economic feasibility of mining the Near Earth Asteroids. PHD thesis, 1997). At present, 14,036 near-Earth objects (NEOs) are known to travel around an orbit close to the Earth, from which 1684 are considered potentially hazardous asteroids (PHAs). In this scenario, may not be surprising that some private companies start considering asteroid mining. In the present study, we report the bulk rare-earth element (REEs, La-Lu) compositions of 38 carbonaceous chondrites as well as 2 R-chondrites, including 5 falls and 35 finds, by using inductively coupled plasma mass spectrometry (ICP-MS) technique. The CI-chondrite-normalized REE patterns show enormous Ce anomalies and large LREE enrichments never described before, attributed to the small sample size and terrestrial contamination. We have also found the characteristic Tm anomalies described by some authors (Acta 163:234–261, 2015; Geochim. Cosmochim. Acta 176:1–17, 2016) attributed to type II CAIs. We conclude that from the point of view of abundances, REEs are not worth mining yet for PGEs may be reasonable. In any case, the current inequality between supply and demand of rare earths is a real problem that will result in large price instabilities for many sectors of the economy, also having negative effects in new technologies and development. Consequently, we envision that space exploration will be a way to find the new resources required to sustain market economy over longer timescales.

We show that carbonaceous chondrite meteorites actively and selectively catalyze the formation of relevant prebiotic molecules from formamide in aqueous media. Specific catalytic behaviours are observed, depending on the origin and composition of the chondrites and on the type of water present in the system (activity: thermal > seawater > pure). We report the one-pot synthesis of all the natural nucleobases, of aminoacids and of eight carboxylic acids (forming, from pyruvic acid to citric acid, a continuous series encompassing a large part of the extant Krebs cycle). These data shape a general prebiotic scenario consisting of carbonaceous meteorites acting as catalysts and of a volcanic-like environment providing heat, thermal waters and formamide. This scenario also applies to the other solar system locations that experienced rich delivery of carbonaceous materials, and whose physical-chemical conditions could have allowed chemical evolution.

A crucial topic in planetology research is establishing links between primitive meteorites and their parent asteroids. In this study we investigate the feasibility of a connection between asteroids similar to 21 Lutetia, encountered by the Rosetta mission in July 2010, and the CH3 carbonaceous chondrite Pecora Escarpment 91467 (PCA 91467). Several spectra of this meteorite were acquired in the ultraviolet to near-infrared (0.3 to 2.2 {\mu}m) and in the mid-infrared to thermal infrared (2.5 to 30.0 {\mu}m or 4000 to ~333 cm^-1), and they are compared here to spectra from the asteroid 21 Lutetia. There are several similarities in absorption bands and overall spectral behavior between this CH3 meteorite and 21 Lutetia. Considering also that the bulk density of Lutetia is similar to that of CH chondrites, we suggest that this asteroid could be similar, or related to, the parent body of these meteorites, if not the parent body itself. However, the apparent surface diversity of Lutetia pointed out in previous studies indicates that it could simultaneously be related to other types of chondrites. Future discovery of additional unweathered CH chondrites could provide deeper insight in the possible connection between this family of metal-rich carbonaceous chondrites and 21 Lutetia or other featureless, possibly hydrated high-albedo asteroids., Comment: 26 pages, 7 figures and 2 tables, Meteoritics and Planetary Science, manuscript #2225 (2016)

The Chelyabinsk meteorite is a highly shocked, low porosity, ordinary chondrite, probably similar to S- or Q-type asteroids. Therefore, nanoindentation experiments on this meteorite allow us to obtain key data to understand the physical properties of near-Earth asteroids. Tests at different length scales provide information about the local mechanical properties of the minerals forming this meteorite: reduced Young's modulus, hardness, elastic recovery, and fracture toughness. Those tests are also useful to understand the potential to deflect threatening asteroids using a kinetic projectile. We found that the differences in mechanical properties between regions of the meteorite, which increase or reduce the efficiency of impacts, are not a result of compositional differences. A low mean particle size, attributed to repetitive shock, can increase hardness, while low porosity promotes a higher momentum multiplication. Momentum multiplication is the ratio between the change in momentum of a target due to an impact, and the momentum of the projectile, and, therefore higher values imply more efficient impacts. In the Chelyabinsk meteorite, the properties of the light-colored lithology materials facilitate obtaining higher momentum multiplication values, compared to the other regions described for this meteorite. Also, we found a low value of fracture toughness in the shock-melt veins of Chelyabinsk, which would promote the ejection of material after an impact and, therefore, increase the momentum multiplication. These results are relevant considering the growing interest in missions to test asteroid deflection, such as the recent collaboration between the European Space Agency and NASA, known as the Asteroid Impact and Deflection Assessment mission., Comment: 2 Tables, 4 Figures, and 19 pages in Astrophysical Journal (2017)

Es descriu l'experiència realitzada en l'assignatura optativa Biomembranes: estudis fisicoquímics del Grau de Farmàcia de la UB. Aquest aspecte comporta formar un grup no molt nombrós d'estudiants i permet realitzar experiències metodològiques noves introduint aspectes de flexibilitat per a estudiants i professors. Es van establir els objectius competencials i es va dissenyar un programa flexible respecte a continguts, a activitats i dimensió espai-temps amb resultats satisfactoris.

We report and describe an L6 ordinary chondrite fall that occurred in Ardon Leon province Spain (longitude 5.5605 degrees W latitude 42.4364 degrees N) on July 9th 1931. The 5.5 g single stone was kept hidden for 83 yr by Rosa Gonzalez Perez at the time an 11 yr old who had observed the fall and had recovered the meteorite. According to various newspaper reports the event was widely observed in Northern Spain. Ardon is a very well preserved fresh strongly metamorphosed (petrologic type 6) and weakly shocked (S3) ordinary chondrite with well equilibrated and recrystallized minerals. The mineral compositions (olivine Fa(23.7 +/ 0.3) low Ca pyroxene Fs(20.4 +/ 0.2)Wo(1.5 +/ 0.2) plagioclase An(10.3 +/ 0.5)Ab(84.3 +/ 1.2)) magnetic susceptibility (log chi = 4.95 +/ 0.05 x10( 9) m(3) kg( 1)) bulk density (3.49 +/ 0.05 g cm( 3)) grain density (3.58 +/ 0.05 g cm( 3)) and porosity (2.5 vol) are typical for L6 chondrites. Short lived radionuclides confirm that the meteorite constitutes a recent fall. The Ne 21 and Ar 38 cosmic ray exposure ages are both about 20 30 Ma similar to values for many other L chondrites. The cosmogenic Ne 22/Ne 21 ratio indicates that preatmospheric Ardon was a relatively large body. The fact that the meteorite was hidden in private hands for 83 yr makes one wonder if other meteorite falls may have experienced the same fate thus possibly explaining the anomalously low number of falls reported in continental Spain in the 20th century.

We report and describe an L6 ordinary chondrite fall that occurred in Ardon, Leon province, Spain (longitude 5.5605 degrees W, latitude 42.4364 degrees N) on July 9th, 1931. The 5.5 g single stone was kept hidden for 83 yr by Rosa Gonzalez Perez, at the time an 11 yr old who had observed the fall and had recovered the meteorite. According to various newspaper reports, the event was widely observed in Northern Spain. Ardon is a very well-preserved, fresh, strongly metamorphosed (petrologic type 6), and weakly shocked (S3) ordinary chondrite with well-equilibrated and recrystallized minerals. The mineral compositions (olivine Fa(23.7 +/- 0.3), low-Ca pyroxene Fs(20.4 +/- 0.2)Wo(1.5 +/- 0.2), plagioclase An(10.3 +/- 0.5)Ab(84.3 +/- 1.2)), magnetic susceptibility (log chi = 4.95 +/- 0.05 x10(-9) m(3) kg(-1)), bulk density (3.49 +/- 0.05 g cm(-3)), grain density (3.58 +/- 0.05 g cm(-3)), and porosity (2.5 vol%) are typical for L6 chondrites. Short-lived radionuclides confirm that the meteorite constitutes a recent fall. The Ne-21 and Ar-38 cosmic ray exposure ages are both about 20-30 Ma, similar to values for many other L chondrites. The cosmogenic Ne-22/Ne-21 ratio indicates that preatmospheric Ardon was a relatively large body. The fact that the meteorite was hidden in private hands for 83 yr makes one wonder if other meteorite falls may have experienced the same fate, thus possibly explaining the anomalously low number of falls reported in continental Spain in the 20th century.