Paris: The slightly altered, slightly metamorphosed CM that bridges the gap between CMs and Cos

A fresh, 1.3 kilo stone was found in Paris. It is a CM chondrite with metal, Fe-sulfide, FeS-rich PCPs and relict mesostasis and is ~3.0 ± 0.1. Petrographic and oxygen isotope evidence indicates that it has affinities with the CO chondrites

Molecular crystallization inhibitors for salt damage control in porous materials. An overview

The use of inhibition chemicals holds the prospect of an efficient strategy to control crystallization in porous materials, thereby potentially contributing to the prevention or mitigation of the salt decay phenomenon in modern as well as historical building materials in a more sustainable manner. In this review, we first provide an essential background on the mechanism of salt crystallization and on the factors influencing this phenomenon; next, we illustrate the mechanism at the basis of the action of crystal growth inhibitors, and critically discuss the major advances in the development of different families of inhibitors, particularly focusing on their influence on salt transport and crystallization within the structure of porous media. Specifically, correlations between the crystallization inhibition processes in porous materials and variables, such as porous substrate composition and properties, contaminant salt type and concentrations, microclimatic conditions, inhibiting solution concentration and properties, and application methods, will be highlighted. Environmental aspects, limitations, and problems associated with some inhibition chemicals are also taken into account. Finally, a survey and a discussion on the most representative experimental techniques and instrumentation available to assess qualitatively and quantitatively the inhibitor effectiveness, as well as recently developed modelling tools are given out

Condensate evolution in the solar nebula inferred from combined Cr, Ti, and O isotope analyses of amoeboid olivine aggregates

Refractory inclusions in chondritic meteorites, namely amoeboid olivine aggregates (AOAs) and Ca-Al-rich inclusions (CAIs), are among the first solids to have formed in the solar system. The isotopic composition of CAIs is distinct from bulk meteorites, which either results from extreme processing of presolar carriers in the CAI-forming region, or reflects an inherited heterogeneity from the Sun's parental molecular cloud. Amoeboid olivine aggregates are less refractory than CAIs and provide a record of how the isotopic composition of solid material in the disk may have changed in time and space. However, the isotopic composition of AOAs and how this composition relates to that of CAIs and later-formed solids is unknown. Here, using new O, Ti, and Cr isotopic data for eight AOAs from the Allende CV3 chondrite, we show that CAIs and AOAs share a common isotopic composition, indicating a close genetic link and formation from the same isotopic reservoir. Because AOAs are less refractory than CAIs, this observation is difficult to reconcile with a thermal processing origin of the isotope anomalies. Instead, the common isotopic composition of CAIs and AOAs is readily accounted for in a model in which the isotopic composition of infalling material from the Sun's parental molecular cloud changed over time. In this model, CAIs and AOAs record the isotopic composition of the early infall, while later-formed solids contain a larger fraction of the later, isotopically distinct infall. This model implies that CAIs and AOAs record the isotopic composition of the Sun and suggests that the nucleosynthetic isotope heterogeneity of the solar system is predominantly produced by mixing of solar nebula condensates, which acquired their distinct isotopic compositions as a result of time-varied infall from the protosolar cloud.Comment: Published gold open access in Earth and Planetary Science Letter

Controlling crystallization damage by the use of salt inhibitors on Malta’s limestone

The main building stone in the Maltese Islands is the Globigerina Limestone, of which the Lower member is commonly used. This occurs in two types, the durable franka and the more easily weathered soll. Two types of fresh franka (bajda -white- and safra -yellow-), as well as fresh soll stone blocks, were obtained, based on the identification by quarry owners. Their designation was confirmed by geochemistry. Physical and mechanical properties of the three were investigated, including uniaxial compressive strength, water absorption by capillarity, permeability and porosimetry. Porosimetry results confirmed outcomes of previous research work. Soll was found to have a lower overall porosity, but a high percentage of small pores with practically no large pores. Some of the tested stones were then treated with a non-toxic phospho-organic compound containing carboxylic moieties as a salt inhibitor and the corresponding non-phosphorylated compound, as aqueous solutions at different concentrations. Both treated and untreated stones were then subject to salt crystallization tests, using sodium sulphate in different concentrations. For the untreated stones, even after only one salt cycle, faster and more pronounced deterioration was observed for the soll samples as opposed to the franka ones. In the case of the treated stones, less deterioration with almost no damage was observed as opposed to non-treated ones. The presence of even very low concentrations of the inhibitor thus helps crystallization to occur on the stone surface and not within the pores. These encouraging results led to the conclusion that salt inhibitors can be used to treat salt-infested stone. Further research in this respect, also using NaCl/NaHCO3, is continuing., ,peer-reviewe

Light noble gas composition of different solar wind regimes: results from genesis

The Genesis mission provided samples of solar wind (SW) from different regions on the Sun. These SW regime samples are important in understanding fractionation processes upon formation and acceleration of the SW to ultimately deduce solar composition from SW values. We present He and Ne isotopic and elemental compositions of the bulk SW (SW of entire collection period) and the 3 major SW regimes: slow (from the ecliptic plane, emanating from above streamers), fast (emanating from coronal holes), and coronal mass ejections (CME). At the conference we will also present Ar data

Mass-fractionation induced by the Genesis solar wind concentrator: Analysis of neon isotopes by UV laser ablation

The solar wind (SW) concentrator, a key instrument onboard the Genesis mission, was designed to provide larger fluences of implanted SW for precise isotope analyses of oxygen and nitrogen [1]. SW ions in the mass range 4–28 amu were accelerated and focused on a “concentrator target” by an electrostatic mirror. This concentration process caused some instrumental mass fractionation of the implanted SW ions as function of the radial position on the target. Correction of this fractionation will be based on a combination of the measured radial fractionation of Ne isotopes with results of simulations of the implantation process using the actual performance of the concentrator and the SW conditions during exposure. Here we present He and Ne abundance and Ne isotopic composition data along one arm of the gold cross that framed the 4 concentrator subtargets

Solar neon released from Genesis aluminum collector duriung stepped uv-laser extraction and step-wise pyrolysis

Earlier this year we reported results of UV-laser stepped raster extractions of Ne and He from Genesis' Al-collector [l]. Since then, using pyrolysis of a 0.005 cm^2 fragment of this material left from the earlier study, we have estimated the efficiency of the UV-laser extraction to be at least 95%. We also analyzed Ne released from the Al-collector by means of stepped pyrolysis. Here we compare these new data with stepped UV-laser extraction and the CSSE results [2]. Figure 1 shows the ^(20)Ne/^(22)Ne ratio extracted from Genesis collectors using these three techniques

One of the earliest refractory inclusions and its implications for solar system history

A ∼175 µm refractory inclusion, A-COR-01 from one of the least altered carbonaceous chondrites, ALHA 77307 (CO3.0), has been found to bear unique characteristics that indicate that it is one of the first solids to have formed at the very birth of the solar system while isotopic reservoirs were still evolving rapidly. Its core is composed mainly of hibonite and corundum, the two phases predicted to condense first from a gas of solar composition, and like many common types of Calcium-, Aluminium-rich Inclusions (CAIs) is surrounded by a rim of diopside. Core minerals in A-COR-01 are very 16O-rich (Δ17OCore = -32.5 ± 3.3 (2SD) ‰) while those in the rim display an O isotopic composition (Δ17ORim = -24.8 ± 0.5 (2SD) ‰) indistinguishable from that found in the vast majority of the least altered CAIs. These observations indicate that this CAI formed in a very 16O-rich reservoir and either recorded the subsequent evolution of this reservoir or the transit to another reservoir. The origin of A-COR-01in a primitive reservoir is consistent with the very low content of excess of radiogenic 26Mg in its core minerals corresponding to the inferred initial 26Al/27Al ratio ((26Al/27Al)0 = (1.67 ± 0.31) × 10-7), supporting a very early formation before injection and/or homogenisation of 26Al in the protoplanetary disk. Possible reservoir evolution and short-lived radionuclide (SLRs) injection scenarios are discussed and it is suggested that the observed isotope composition resulted from mixing of a previously un-observed early reservoir with the rest of the disk

Argon and neon in Genesis aluminum-coated sapphire collectors from regime arrays

Here we report Ar results from the aluminum on sapphire (AloS) bulk regime samples, from which Ne results were obtained [1]. Ar measurements from other regimes are in progress