Origin and age of the earliest Martian crust from meteorite NWA 7533.

The ancient cratered terrain of the southern highlands of Mars is thought to hold clues to the planet's early differentiation, but until now no meteoritic regolith breccias have been recovered from Mars. Here we show that the meteorite Northwest Africa (NWA) 7533 (paired with meteorite NWA 7034) is a polymict breccia consisting of a fine-grained interclast matrix containing clasts of igneous-textured rocks and fine-grained clast-laden impact melt rocks. High abundances of meteoritic siderophiles (for example nickel and iridium) found throughout the rock reach a level in the fine-grained portions equivalent to 5 per cent CI chondritic input, which is comparable to the highest levels found in lunar breccias. Furthermore, analyses of three leucocratic monzonite clasts show a correlation between nickel, iridium and magnesium consistent with differentiation from impact melts. Compositionally, all the fine-grained material is alkalic basalt, chemically identical (except for sulphur, chlorine and zinc) to soils from Gusev crater. Thus, we propose that NWA 7533 is a Martian regolith breccia. It contains zircons for which we measured an age of 4,428 ± 25 million years, which were later disturbed 1,712 ± 85 million years ago. This evidence for early crustal differentiation implies that the Martian crust, and its volatile inventory, formed in about the first 100 million years of Martian history, coeval with earliest crust formation on the Moon and the Earth. In addition, incompatible element abundances in clast-laden impact melt rocks and interclast matrix provide a geochemical estimate of the average thickness of the Martian crust (50 kilometres) comparable to that estimated geophysically.

Early crustal processes revealed by the ejection site of the oldest martian meteorite.

The formation and differentiation of the crust of Mars in the first tens of millions of years after its accretion can only be deciphered from incredibly limited records. The martian breccia NWA 7034 and its paired stones is one of them. This meteorite contains the oldest martian igneous material ever dated: ~4.5 Ga old. However, its source and geological context have so far remained unknown. Here, we show that the meteorite was ejected 5-10 Ma ago from the north-east of the Terra Cimmeria-Sirenum province, in the southern hemisphere of Mars. More specifically, the breccia belongs to the ejecta deposits of the Khujirt crater formed 1.5 Ga ago, and it was ejected as a result of the formation of the Karratha crater 5-10 Ma ago. Our findings demonstrate that the Terra Cimmeria-Sirenum province is a relic of the differentiated primordial martian crust, formed shortly after the accretion of the planet, and that it constitutes a unique record of early crustal processes. This province is an ideal landing site for future missions aiming to unravel the first tens of millions of years of the history of Mars and, by extension, of all terrestrial planets, including the Earth.

Origin and metamorphic redistribution of silicon, chromium, and phosphorus in the metal of chondrites.

Chromium, silicon, and phosphorus concentrations of 0.1 to 1 percent by weight are common in metal grains in the least metamorphosed ordinary and carbonaceous chondrites. These concentrations are fairly uniform within single chondrules (but different from chondrule to chondrule) and are inversely correlated with the fayalite concentrations of the chondrule olivines. This relation shows that these chromium, silicon, and phosphorus concentrations could not have been established by condensation or equilibration in the solar nebula but are the result of metal-silicate equilibration within chondrules. Two generations of inclusions made by the exsolution of those elements have been identified: One formed during chondrule cooling and the other formed during metamorphism. The distribution and composition of the latter in type 3 to type 5 chondrites are consistent with increasing metamorphism relative to type 2 and type 3.0 material.

Tissint martian meteorite: a fresh look at the interior, surface, and atmosphere of Mars.

Tissint (Morocco) is the fifth martian meteorite collected after it was witnessed falling to Earth. Our integrated mineralogical, petrological, and geochemical study shows that it is a depleted picritic shergottite similar to EETA79001A. Highly magnesian olivine and abundant glass containing martian atmosphere are present in Tissint. Refractory trace element, sulfur, and fluorine data for the matrix and glass veins in the meteorite indicate the presence of a martian surface component. Thus, the influence of in situ martian weathering can be unambiguously distinguished from terrestrial contamination in this meteorite. Martian weathering features in Tissint are compatible with the results of spacecraft observations of Mars. Tissint has a cosmic-ray exposure age of 0.7 ± 0.3 million years, consistent with those of many other shergottites, notably EETA79001, suggesting that they were ejected from Mars during the same event.

A protective role of a cholesteryl ester transfer protein gene variant towards ischaemic stroke in Sardinians.

OBJECTIVES: Cholesteryl ester transfer protein (CETP) plays a key role in the metabolism of high-density lipoprotein (HDL), a strong, inverse, independent risk factor for cardiovascular disease. We sought to investigate the relationship between a common variant of CETP gene, the Taq1 B polymorphism, that has been previously associated with CETP blood concentrations, and the risk of ischaemic stroke in a genetically homogenous population from the Sardinia island, Italy. This population has been previously shown to be a highly conservative sample. DESIGN: A total of 215 cases of ischaemic stroke and 236 controls were selected and characterized for the CETP Taq1 B polymorphism. Allele and genotype frequencies were compared amongst cases and controls. RESULTS: Age, hypertension and hypercholesterolaemia were independent risk factors for stroke in this cohort. We found that presence of the CETP Taq1 B2 allele was associated with a significantly decreased risk of ischaemic stroke when assuming a recessive mode of inheritance (OR 0.55, 95% CI = 0.34-0.90, P = 0.017). This result was confirmed by multivariate analysis, after adjustment for age, presence of hypertension and hypercholesterolaemia (OR 0.53, 95% CI = 0.32-0.88, P = 0.014). By performing separate analysis for gender we found that the effect was present in females but not in males, with a significant sex-CETP gene variant interaction for both recessive (P = 0.005) and additive (P = 0.029) modes of inheritance. CONCLUSIONS: Our data suggest that the Taq1 B2 allelic variant of the CETP gene may be associated, as a protective factor, with occurrence of ischaemic stroke. Further studies are needed to further elucidate the clinical implications of our finding.

Inflammatory biomarkers in blood of patients with acute brain ischemia.

Although many failed surrogate markers are provided in the literature, inflammation may contribute to the outcome of ischemic stroke. In 50 consecutive patients with acute ischemic stroke, in the absence of symptoms and signs of concomitant infection, we evaluated a panel of biomarkers reported to be variably associated with brain ischemia, and correlate their serum level with the brain lesion volume and clinical outcome. Infarct size was calculated on computed tomography (CT) scans by means of the Cavalieri's method. Neurological impairment was scored by using the Glasgow Coma Scale, Glasgow Outcome Scale and National Institutes of Health (NIH) scales at stroke onset and 3-month follow-up. Some markers showed a direct significant correlation with both initial and final NIH scale and with infarct size, particularly tumor necrosis factor alpha (TNF-alpha) (P=0.002), intercellular adhesion molecule-1 (P<0.01) and matrix metalloproteinase-2/9 (P=0.001). In contrast to previous reports, interleukin-6 (IL-6) serum level showed a significant inverse correlation with both final neurological impairment and infarct size (P<0.001). This novel finding allows us suggesting that IL-6, in the context of a complex pro-inflammatory network occurring during stroke, is associated with neuroprotection rather than neurotoxicity in patients with ischemic brain injury.