Maghreb Research Articles

Determination of olivine fayalite–forsterite composition in ordinary chondrites by X‐ray diffraction

AbstractOrdinary chondrites account for the majority of the described meteorites on Earth. To expand the toolbox of analytical techniques available to describe such specimens, this study evaluates the application of a previously described fayalite determination method by X‐ray diffraction (XRD) to equilibrated ordinary chondrites. A suite of ordinary chondrites, ranging from petrologic type 4 to 6, and types H, L, and LL were analyzed by both XRD and electron probe microanalysis. A comparison of the results shows good agreement between the two methods with an R2 of 0.95 and better agreement for homogenous ordinary chondrites above petrographic grade 4. The differences between the two methods can largely be attributed to analytical uncertainty, as well as differences between point and bulk sampling techniques. These differences were used to identify two polymict breccia samples, Peace River and Northwest Africa 10946. Of note is the effect of exposure of the ordinary chondrites to room temperature and humidity conditions after sample preparation (powdering) and the impact on measured fayalite content by XRD. As such, it is recommended that XRD analyses of meteorites be performed immediately after sample preparation.

Detection and Isolation of Sindbis Virus from Field Collected Mosquitoes in Timimoun, Algeria.

Sindbis virus (SINV) is a zoonotic alphavirus (family Togaviridae, genus Alphavirus) that causes human diseases in Africa, Europe, Asia, and Australia. Occasionally, SINV outbreaks were reported in South Africa and northern Europe. Birds are the main amplifying hosts of SINV, while mosquitoes play the role of the primary vector. Culex mosquitoes were collected in Algeria and subsequently tested for SINV. SINV RNA was detected in 10 pools out of 40, from a total of 922 mosquitoes tested. A strain of SINV was isolated from a pool displaying high viral load. Whole-genome sequencing and phylogenetic analysis showed that the SINV Algeria isolate was most closely related to a Kenyan strain. This was the first record of SINV in Algeria and more broadly in northwestern Africa, which can be a potential risk for human health in the circulating area. Further studies are needed to measure the impact on public health through seroprevalence studies in Algeria.

A window into atmospheric escape on early Mars provided by argon isotopes in a Martian meteorite

Novel analytical approaches to determining the trapped 38Ar/36Ar ratio of gases contained within Martian meteorites are presented and applied to the Martian regolith breccia Northwest Africa (NWA) 7034 and paired stone NWA 11220. The resulting data indicate that extensive mass-dependent fractionation of atmospheric Ar may have occurred within 150 million years of planetary formation, ostensibly as a result of diffusion-limited hydrodynamic escape. The inferred fractional loss of Ar and lighter atmospheric constituents exceeds 50%. These data suggest that volatiles derived from planetary outgassing and/or impactors may dominate the present abundance of atmospheric Ar.

Evolved components in the eucrite parent body: Records in the layered eucrite Northwest Africa 8021

AbstractIn this study, we report the petrography and mineralogy of a brecciated eucrite Northwest Africa (NWA) 8021, which shows a locally layered texture with one layer containing graphic clasts and Si,Ti‐rich regions. The graphic clasts contain rod‐like grains of silica phases, augite, K‐feldspar, and Ca‐phosphate minerals included in anorthite. Some of the clasts contain relatively coarse grains of quartz, K‐feldspar, and augite, which are chemically different from the rod‐like phases, indicating different origins. All of the augite grains in the graphic clasts have rare earth element (REE) concentrations higher than those in typical eucrites. The bulk Na2O+K2O contents of the graphic clasts are higher than typical eucrites. All of these chemical features indicate that the graphic clasts were probably derived from an evolved parent rock. Low‐degree partial melting of the eucritic crust (<10%) is required to generate a melt equilibrated with the REE‐rich rod‐like pyroxene from the graphic clasts. The Si,Ti‐rich regions contain high abundances of silica phases (~52 vol%) and ilmenite (~9 vol%), probably derived from an evolved Si,Ti‐rich rock (dacite). The evolved components observed in NWA 8021 are different from other evolved components observed in howardites and indicate more diverse evolution in the eucrite parent body than previously thought.

Updated Neogene mammalian biochronology and biogeography of Morocco

ABSTRACT The mammalian localities of the upper Neogene in Morocco are now relatively more numerous following the discoveries in recent decades. Most of these Mio-Pliocene deposits occur in formations in continental basins and have yielded almost exclusively micromammals. Only Beni Mellal, Guefaït-4, Ahl Al Oughlam and Tizi N’Taddert are the only localities that have yielded abundant remains of large mammals from the Neogene in Morocco. The data acquired from all of these deposits currently make it possible to better understand the stratigraphy of the Mio-Pliocene sedimentary basins and to establish correlations between these fossiliferous localities. However, these localities are not distributed stratigraphically in a regular way so as to mark out the different stages of this period. The locations of the Lower Miocene are unknown. Those of the Middle Miocene are interesting although few in number. The Upper Miocene localities are more numerous and are distributed between the equivalent of biozones MN9 to MN13. Late Miocene and early Pliocene localities document exchanges of fauna between southwestern Europe and northwestern Africa. Pliocene localities are rare and particularly those which have provided macro-mammals. Although extremely rare, radiometric dating of sections in certain basins has enabled precise ages to be attributed to many deposits.

Wildlife‐vehicle collisions in Moroccan Atlantic Sahara: Impact on resident species and Afro‐Palearctic birds for conservation purposes

AbstractIn this study, we described the temporal and spatial patterns of wildlife‐vehicle collisions in Dakhla‐Laayoune regions, using counts from cars for two years (2018–2021). A total of 462 roadkills were documented (monthly average of 0.075 roadkills/km), comprising 16 species, including mammals (residents), reptiles (residents), and birds (residents and migrants). Seasonal abundance and diversity of roadkills revealed a high peak during breeding and migration periods for all species. The generalised linear mixed models indicated that wildlife‐vehicle accidents have a higher probability of occurrence close to breeding and feeding sites and road sections with increased vegetation cover. Similarly, road collisions were higher close to migration routes and during breeding periods. Our study provides the first and only detailed results on wildlife road collisions in Morocco. Data gathered from this study provide valuable information for conservation measures of the most affected Moroccan species and Palearctic migrant birds which are crossing between Europe and Africa. Moreover, our data provide a new window of large‐scale comparative studies addressing the impacts of the infrastructures on biodiversity in the entire Atlantic coasts of Northwest Africa. Detailed studies on the local population dynamics of highly affected species are urgently needed to conclude whether these levels of road mortality are supportable.

Carbon remineralization by small mesopelagic and bathypelagic Stomiiforms in the Northeast Atlantic Ocean

The organic carbon resulting from photosynthesis in the upper ocean is transferred downward through the passive sinking of organic particles, physical mixing of particulate and dissolved organic carbon as well as active flux transported by zooplanktonic and micronektonic migrants. Several meso- and bathypelagic organisms feed in shallower layers during the nighttime and respire, defecate, excrete and die at depth. Recent studies suggest that migrant micronekton transport similar amounts of carbon to migrant zooplankton. However, there is scarce information about biomass and carbon flux by non-migratory species in the mesopelagic and bathypelagic zones. The non-migratory bristlemouth fishes (Cyclothone spp.) and partial migrator (A. hemigymnus) remineralise organic carbon at depth, and knowledge about this process by this fauna is lacking despite them having been referred to as the most abundant vertebrates on Earth. Here we show the vertical distribution of biomass and respiration of non-migratory mesopelagic fishes, during day and night, using the enzymatic activity of the electron transfer system (ETS) as a proxy for respiration rates. The study is focused on five Cyclothone species (C. braueri, C. pseudopallida, C. pallida, C. livida and C. microdon) and Argyropelecus hemigymnus. The samples were taken on a transect from the oceanic upwelling off Northwest Africa (20° N, 20° W) to the south of Iceland (60° N, 20° W). Cyclothone spp. showed, by far, the largest biomass (126.90 ± 86.20 mg C·m−2) compared to A. hemigymnus (0.54 ± 0.44 mg C·m−2). The highest concentrations of Cyclothone spp. in the water column were observed between 400 and 600 m and from 1000 to 1500 m depths, both during day and night. For the different species analysed, ETS activity did not show significant differences between diurnal and nocturnal periods. The total average specific respiration of Cyclothone spp. (0.02 ± 0.01 d-1) was lower than that observed for A. hemigymnus (0.05 ± 0.02 d-1). The average carbon respiration of Cyclothone spp. was 2.22 ± 0.81 mg C·m−2·d-1, while it was much lower for A. hemigymnus (0.04 ± 0.03 mg C·m−2·d-1). The respiration of Cyclothone spp. was lower in the bathypelagic than in the mesopelagic zone (0.84 ± 0.48 vs 1.36 ± 1.01 mg C·m−2·d-1, respectively). These results, to our knowledge, provide the first account of remineralisation by this community in the meso and bathypelagic zones of the ocean.

Spinel in CV chondrules: Investigating precursor legacy and chondrule thermal histories

AbstractIn carbonaceous chondrites, Mg‐spinel (MgAl2O4) grains are ubiquitous in refractory inclusions but rarely reported in chondrules, where they may correspond to minerals either (i) inherited from chondrule precursors or (ii) crystallized from chondrule melts. Here, we report high‐current quantitative electron microprobe measurements and secondary ion mass spectrometry oxygen isotopic analyses of Mg‐spinel‐bearing chondrules in the CV3 carbonaceous chondrites Northwest Africa 10235 and Allende. Compared to spinels in refractory inclusions, chondrule spinels are characterized by higher Cr contents and 16O‐poorer oxygen isotopic signatures (∆17O ≡ δ17O−0.52 × δ18O, from −2 to −6‰). Because the similar Δ17O values of chondrule olivine and spinel crystals imply their comagmatic origin, we applied a geothermometer based on the Al‐Cr distribution between these minerals to determine their crystallization temperatures. The calculated temperatures range from 1200 to 1640 °C (mean = 1470 °C), most being lower than the estimated liquidus temperature of porphyritic chondrules (~1600 °C). Our results suggest that chondrules experienced relatively slow cooling rates (slower than a few hundreds of °C h−1), which is in good agreement with models of chondrule formation invoking nonlinear or two‐stage cooling rates.

Distinct mtDNA lineages in free-ranging Ammotragus(aoudad) from the United States indicate multiple introductions from northern Africa.

Translocation records indicate aoudad (Ammotragus lervia) populations in the United States are a product of multiple human‐mediated introductions. Two mitochondrial markers (cytochrome b, cytb; displacement loop, D loop) and one nuclear gene (prion protein gene exon 3, PRNP) were used to determine: (1) genetic variation, (2) if genetic units correspond to taxonomic designations, (3) the number and geographic origin of translocations, and (4) divergence times. Three phylogenetic analyses (Bayesian inference, maximum likelihood, and parsimony) produced similar topologies with two clades (I and II). Clade I contained progeny of individuals resulting from introductions to Texas and Spain, and individuals from Algeria. Individuals in Clade II were progeny of past introductions to the United States and Europe, and northern Algeria. Clade II was subdivided into two subclades (A and B) representing two haplogroups. No genetic variation was detected in the PRNP sequences. Three haplogroups appeared to correspond to the subspecies A. l. lervia and A. l. sahariensis whose native distribution includes northwestern Africa. Network analyses assigned haplogroups to two major groups similar to those depicted in the phylogenetic analyses. Genetic distances ranged from 0.80% to 5.17% and 2.99% to 15.42% for cytb and D loop, respectively; and were higher than normally recovered for caprids, warranting a reexamination of subspecific status. Divergence dates indicated a major split between A. l. lervia and A. l. sahariensis circa 2.38 mya. Together, the high level of genetic divergences among US populations and apparent presence of two subspecies of aoudad in the United States support the hypothesis of multiple introductions from multiple sources.

Performances of climatic indicators from seasonal forecasts for ecosystem management: The case of Central Europe and the Mediterranean

Climate change is affecting the interannual variability and the seasonal cycle for key meteorological variables, as well as the frequency, intensity, duration and timing of out-of-the-norm and extreme events. In such a context, seasonal forecasts (i.e., climate predictions from a few weeks to several months ahead) are compelling instruments able to anticipate upcoming climate risks and guide tactical decisions. In this study, we assess the performance of seasonal forecasts for the summer period across Central Europe and the Mediterranean region in predicting some key indicators serving agriculture and forestry sectors, i.e., Potential EvapoTranspiration (PET), Potential Soil Moisture Deficit (PSMD), and Fire Weather Index (FWI). We exploit authoritative climate data from Copernicus Climate Data Store, i.e., ERA5 reanalyses and hindcasts from CMCC SPSv3 and ECMWF SEAS5 seasonal prediction systems (SPSs), to evaluate, using both deterministic and probabilistic evaluation scores, differences in performance across the two SPSs, two start dates (March and May) and four correction techniques applied to overcome modelling bias, namely bias correction (BC), calibration (CAL), quantile mapping (QM) and detrending (DET). Results show that seasonal predictions of PET perform better in Western and Eastern Europe and some areas of North Africa. PSMD predictions follow a similar spatial pattern as PET, except that for some areas in Central (Eastern) Europe in which the performance increases (decreases). FWI predictions reveal better results in some areas of the Iberian Peninsula, North-Western Africa, Balkan Peninsula, and Ukraine. Results also suggest that QM might be the most suitable technique for bias correction. Furthermore, the start date of the forecast might imply varying correlation significance, with the start date closest to the forecasted period not always being the best. Overall, our study suggests the potential usefulness of seasonal forecasts for decision making under different geographical and environmental contexts, considering sensitivity inherent to different processing chains.

Petrogenesis of Northwest Africa 8686: A ferroan olivine‐phyric shergottite

AbstractNorthwest Africa (NWA) 8686 is an olivine‐phyric shergottite containing up to ~500 μm long olivine crystals in a fine‐grained groundmass of augite, pigeonite, and maskelynite, with accessory merrillite, pyrrhotite, and oxides. Bulk rock and mineral major and trace element concentrations are reported for NWA 8686, along with bulk rock highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundances and 187Re‐187Os data. Based on its mineralogy, texture, and bulk rock rare earth element (REE) abundances, NWA 8686 is classified as an intermediate olivine‐phyric shergottite. It is notable for having some of the most ferroan olivine macrocrysts (forsterite content = 51.5 ± 3.5) of any olivine‐phyric shergottite. Olivine is absent from the NWA 8686 groundmass, which is unique for olivine‐phyric shergottites, and the calculated groundmass composition is also not olivine normative. The bulk meteorite has a low Mg# of 59 yet has HSE in broadly chondritic proportions (~0.005 × CI chondrite). The bulk rock REE pattern for NWA 8686 shows depletions in both the light and heavy REE relative to the middle REE. Compiled olivine and bulk rock data for olivine‐phyric shergottites indicate that olivine macrocrysts in almost all these meteorites are the result of entrainment of antecrysts or xenocrysts. The combination of low Mg# and chondritic HSE signatures in NWA 8686 means that it may have been formed either from the mixing between an evolved lava and early‐formed HSE‐rich phases such as Os‐Ir alloys or by the melting of a low Mg# mantle source with chondritic HSE abundances. The elevated Gd/Yb ratio in both NWA 8686 and other intermediate olivine‐phyric shergottites indicates that garnet was involved as either a residual or fractionating phase in their petrogenesis.

Cratonic keels controlled the emplacement of the Central Atlantic Magmatic Province (CAMP)

Large Igneous Provinces (LIPs) are exceptionally voluminous magmatic events frequently related to continental break-up, global climate changes and mass extinctions. One interesting aspect of many LIPs is their spatial proximity to cratons, begging the question of a potential control of thick lithosphere on their emplacement. In this study, we investigate the relationship between the emplacement of the Central Atlantic Magmatic Province (CAMP) and the thick lithospheric mantle of the Precambrian cratons that formed the central portion of Pangea and are currently located on the continents surrounding the Central Atlantic Ocean. CAMP outcrops are frequently located over the margins of the thick cratonic keels, as imaged by recent tomographic studies, suggesting a role of lithosphere architecture in controlling magma genesis and emplacement. Here we focus on CAMP dykes and sills from the Hank, Hodh, and Kaarta basins in North-Western Africa (NW-Africa, Mali and Mauritania) emplaced at the edge of the Reguibat and Leo-Man Shields. The investigated intrusive rocks show compositions similar to most CAMP magmas, in particular those of the Tiourjdal geochemical group, limited to NW-Africa, and of the Prevalent group, occurring all over the CAMP. Geochemical modelling of CAMP basalts requires a Depleted MORB Mantle (DMM) source enriched by recycled continental crust (1-4%) and melting beneath a lithosphere of ca. 80 km in thickness. On the contrary, melting under a significantly thicker lithosphere (>110 km) does not produce magmas with compositions similar to those of CAMP basalts. This suggests that CAMP magmatism was likely favoured by decompression-induced partial melting of the upwelling asthenospheric mantle along the steep lithospheric boundaries of stable cratons. The architecture of the pre-existing lithosphere (i.e., the presence of stable thick cratonic keels juxtaposed to relatively thinner lithosphere) appears to have been a critical factor for localizing mantle upwelling and partial melting during extensive magmatic events such as in the CAMP.

A READING OF THE FEATURES OF THE ALMOHAD POLITICAL PROJECT AND THE EXPERIENCE OF ‎MOVING FROM THE CONCEPT OF THE GROUP TO THE CONCEPT OF THE STATE

Although the Arab region and the Islamic world witnessed a number of Islamic political experiences that played ‎a prominent role in the historical paths of this vast geography, the Almohad political experience remains the ‎most important distinguished political projects that emerged in the Islamic Maghreb region, as it played an ‎active role in the map of balances at the regional and international levels. This experiment was launched as a ‎religious reform movement led by Muhammad bin Tumart, who believed that a serious political project could ‎not be established in the region without launching a process of broad religious reform due to a reality that was ‎overshadowed by ignorance of religion, and in which myths and deviations spread. Indeed, Ibn Tumart was ‎able to lay the foundations for this reform movement, to later develop and turn into a political movement, ‎which was then able, thanks to Abdel-Moumen bin Ali, to overthrow the Almoravid state and to transfer the ‎Almohad political project from the narrow concept of the group to the broad concept of the state. Therefore, ‎regardless of the accusations that Ibn Tumart was accused of regarding his claim of Mahdism and the ‎fabrication of false prophetic hadiths, the experience of his movement remains a different one, worthy of study ‎and standing on its most important intellectual and political characteristics and advantages. The Almohad ‎political project was a strategic choice that affected the nature of balances and the geopolitical and strategic ‎map of the Islamic West region, which was characterized by intertwining and overlapping during the medieval ‎period. From this logic, we will, in this research, study the political project from the foundation stage in the era of ‎Ibn Tumart to the date of the death of his successor, Abd al-Mumin ibn Ali in the year 558 AH.‎‏ ‏‎ We will discuss ‎this research in three main topics: First, the formation of the Almohad political project and the features of the ‎first founding phase / secondly the death of Ibn Tumart and the features of the second founding phase with ‎Abdul Mumin bin Ali / Thirdly, the end of the Almoravids and the third founding phase of the Almohad project ‎in the era of the believer‎.

Secular Variability of the Upwelling at the Canaries Latitude: An Instrumental Approach

AbstractIn this research we make use of historical wind direction observations to assemble an instrumental upwelling intensity index (the so‐called Directional Upwelling Index [DUI]) for the coast of Northwest Africa between 26° and 33°N and from 1825 to 2014. The DUI is defined as the persistence of the alongshore winds at the coast and unlike other upwelling indices, it relies on observed wind direction solely, avoiding the suspected bias toward increasing wind speed of historical wind observations documented in previous research. We have found that between June and October, when the upwelling intensity in the area is at its seasonal maximum, the persistence of the north‐easterlies measured by the DUI is significantly related to the alongshore wind stress and subsequently with Sea Surface Temperature anomalies at the coast of NW Africa. The analysis of the DUI record does not display a consistent long‐term trend but an oscillatory behavior. At interannual time scales this variability can be linked to the changes in the strength and location of the subtropical north Atlantic high‐pressure center and at multidecadal scales, the upwelling seems mainly driven by the Atlantic Multidecadal Variability through the modulation exerted by this climatic pattern on the intensity of the Saharan low.

A Review of the "Black Beauty" Martian Regolith Breccia and Its Martian Habitability Record.

The regolith breccia Northwest Africa (NWA) 7034 and paired samples are unique meteorite representatives of the martian crust. They are water rich, lithologically varied, and preserve the oldest martian zircon grains yet discovered that formed ca. 4500-4300 Ma. The meteorite thus provides us with an invaluable record of the crustal and environmental conditions on early Mars. Resetting of some radioisotopic chronometers occurred in response to a major thermal disturbance event ca. 1500-1400 Ma, likely caused by an impactor that brecciated and redeposited NWA 7034 near the surface in an ejecta blanket. Lithologies comprising NWA 7034 were then aqueously altered by a long-lasting impact-induced hydrothermal system, before being excavated and ejected by a subsequent impact at ca. 5-15 Ma. This review compiles chronological and petrological information into an overarching geochronological summary for NWA 7034 and paired samples. We then provide a synopsis for the volatile (H2O, C) inventory and hydrothermal alteration history of NWA 7034. From this geochronological history and volatile inventory, we interpret and assess two potential periods of martian habitability: (1) an early window of pre-Noachian planetary habitability, and (2) impact-derived hydrothermal systems that allowed intermittent habitable crater environments well into the Amazonian.

First occurrence of Psammophis (Serpentes) from Europe witnesses another Messinian herpetofaunal dispersal from Africa - biogeographic implications and a discussion of the vertebral morphology of psammophiid snakes.

We here describe abundant new snake material from the late Miocene (MN 13) of Salobreña, Spain. Vertebral morphology suggests a referral of the specimens to the extant psammophiid Psammophis, documenting the first occurrence of this genus in Europe. The diversity and disparity across the vertebral morphology of different psammophiid genera are discussed. We identify vertebral features that could diagnose Psammophis and therefore enable the recognition of the genus in the fossil record. A comparison of the new Spanish form with other taxa is conducted. We provide a detailed review of the psammophiid fossil record. Material previously described from the middle Miocene of Beni Mellal, Morocco is here tentatively referred to as ?Psammophis sp., an action that renders that occurrence as the oldest (probable) record of the genus and Psammophiidae as a whole, providing thus a potential calibration point. On the other hand, Eastern European Pliocene material that had been previously supposedly referred to Psammophis is here discarded as being rather fragmentary, not affording any more precise determination. The two psammophiid genera Psammophis and Malpolon appear almost simultaneously in the European fossil record (MN 13), with the former achieving only a short-lived and apparently geographically limited distribution in the continent, while the latter still exists in its modern herpetofauna. We assess biogeographic implications of the new find, suggesting a direct dispersal event from northwestern Africa to the Iberian Peninsula during the late Miocene, facilitated by the Messinian Salinity Crisis.

Chemical study of group IIIF iron meteorites and the potentially related pallasites Zinder and Northwest Africa 1911

Group IIIF was established as a magmatic iron-meteorite group based on similar Ga and Ge abundances, unusually high Ga/Ge ratios, and the IIIAB-like interelement trends in its members; recent Mo and Ru isotopic data indicate that three of its members exhibit the isotopic signature of carbonaceous-chondrite (CC) irons. Here we report the elemental chemistry of this group and model its crystallization history. Included are new elemental data for IIIF irons acquired by both instrumental neutron activation analysis (INAA) and laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS). A fractional-crystallization model was used to evaluate the IIIF compositional trends for 19 elements and was unable to explain the observed fractionation trends for several key elements (Co, Ga, Ge). In particular, the inability of this model to match Co in the IIIF irons is striking because (1) group IIIF has the widest Co variation among all magmatic iron groups and (2) none of the tested initial S contents (0–20 wt.%) explains both the wide Co variation and steep Co-As slope. Attempts to fit subsets of the IIIF irons were also unsuccessful. In addition, group IIIF has the greatest variety of structural classes and kamacite bandwidths among all established magmatic iron groups. If the IIIF irons constitute a coherent group, they were derived from a parent body that experienced more complex processes than simple fractional crystallization of the core.The Zinder and Northwest Africa (NWA) 1911 pyroxene-bearing pallasites were recently suggested to be related to group IIIF based on their Ga and Ge contents, and we completed a petrographic study of the pallasite silicates and LA-ICP-MS analyses of their metal fractions. The two pallasites are related to one another: they have nearly identical mineralogical, elemental and O-isotopic compositions in their silicates and metals. Their metallic compositions resemble those of the IIIF irons Moonbi, St. Genevieve County, and Cerro del Inca, but their O-isotopic compositions resemble those of non-carbonaceous (NC) achondrites. Additional isotopic measurements are needed to test the potential genetic relationship to group IIIF.

Impact and habitability scenarios for early Mars revisited based on a 4.45-Ga shocked zircon in regolith breccia

After formation of a primordial crust, early impacts influenced when habitable conditions may have occurred on Mars. Martian meteorite Northwest Africa (NWA) 7034 is a regolith breccia that contains remnants of the earliest Martian crust. The paucity of shock deformation in NWA 7034 was previously cited as recording a decline in giant impacts by 4.48 billion years and evidence for habitable Mars by 4.2 billion years ago. We present new evidence of high-pressure shock effects in a 4.45–billion year–old zircon from the matrix of NWA 7034. The zircon contains {112} shock twins formed in the central uplift of a complex impact structure after 4.45 billion years and records impact pressures of 20 to 30 gigapascals. The zircon represents the highest shock level reported in NWA 7034 and paired rocks and provides direct physical evidence of large impacts, some potentially life-affecting, that persisted on Mars after 4.48 billion years.

The Neutron Energy Spectra of Lunar Meteorites Evaluated from Sm and Er Isotopic Compositions

Abstract Cosmic-ray exposure records of 13 lunar meteorites, Dhofar 081, Dhofar 910, Dhofar 911, Northwest Africa (NWA) 482, NWA 2995, NWA 2996, NWA 3136, NWA 3163, NWA 4472, NWA 4734, NWA 4884, NWA 4932, and NWA 4936, were characterized from the abundances of spallogenic (10Be and 26Al) and neutron-captured (36Cl, 41Ca,150Sm, and 168Er) nuclides produced by cosmic-ray irradiation. Assuming a single-stage irradiation model for individual meteorites, 11 of the 13 meteorites had resided at shallow depths in the range of 55 to 330 g cm−2 from the lunar surface and experienced cosmic-ray irradiations for 140–870 Ma on the Moon. In contrast, 2 of the 13 meteorites, Dhofar 911 and NWA 4932, cannot be simply explained by a single-stage irradiation, but need at least two-stage irradiation on the Moon. Furthermore, the neutron fluences of thermal and epithermal energy regions for individual meteorites were quantified from a combination of the isotopic shifts of 149Sm–150Sm and 167Er–168Er, respectively. Our estimates gave 8–11 times higher epithermal neutron fluences (1.7–13.7 × 101 7 neutrons cm−2) than the thermal neutron fluences (0.65–13.8 × 1016 neutrons cm−2) for 9 of the 13 meteorites, which are consistent with those from the lunar regolith materials in our previous study. This result also supports the long cosmic-ray irradiation of most lunar meteorites on the surface of the Moon.

Western Sahara: deep differences over conflict settlement

The conflict in Western Sahara has been going on for thirty-five years, and neither side has won. The parties to the conflict are in an all-or-nothing logic regarding the outcome of this conflict: Morocco preaches the autonomy of the Sahara as the part of the kingdom, and the Algerians and Saharans from the Frente Polisario waives the demands for autonomy. However, in the absence of a clear victory of one of the participants, the political solution need necessarily include a compromise reflecting the balance of power. In an effort to pacify and develop a region that could become a haven for Al-Qaeda in the Islamic Maghreb, Washington, Paris and Madrid could support the new Representative of the Secretary-General in finding a solution that could satisfy all parties, giving this result aspects of compromise. Nevertheless, they will have to take into account both the Saharans as a whole and the geostrategic balance of the region. This article discusses the problems of decolonization and interethnic conflicts. This conflict concentrates the opposition of several geopolitical blocs in one place. On the one hand, he opposes two regional powers: Morocco and Algeria. On the other hand, it opposes two blocs consisting of Morocco and Western countries, against Algeria, a traditional ally of Russia, and large African countries such as Nigeria. This article highlights the inadequacy of international organizations. The issue of stabilizing the situation in Western Sahara is even more important today in the context of Islamic terrorism in the Sahel. Terrorism is spreading in economically and politically unstable countries. The question of the independence of Western Sahara or its integration as an autonomous territory within Morocco must be resolved before terrorism intervenes in Sahari affairs.