Towards the isotopic measurement of solar wind carbon in the Genesis silicon target

We report a current stage of the carbon isotope measurements in the Genesis Si target

Application of semiconductor industry cleaning technologies for Genesis sample collectors

Genesis array collectors recovered after the sub-nominal landing have been exposed to particulate and molecular contamination. In this study, semiconductor industry based cleaning technologies are being evaluated for their efficacy in contaminant removal

Gujba: A new Bencubbin-like meteorite fall from Nigeria

Gujba is a new Bencubbin-like meteorite fall enriched in N-15 and consisting (in vol.%) of 41% metal nodules, 20% large light-colored silicate nodules and 39% dark-colored, C- and silicate-rich matrix

Isheyevo Meteorite: Genetic link between CH and CB chondrites?

Based on the mineralogy, petrography, bulk chemical, oxygen, and nintrogen isotopic compositions and 40Ar-39Ar age, Isheyevo is genetically related to CH and CB carbonaceous chondrites and provides a link between these group of pristine meteorites

The light element geochemistry of Yamato-793605

Carbon, nitrogen, neon and argon abundances and isotopic compositions have been determined by stepped combustion-mass spectrometry on aliquots of the lherzolitic shergottite Yamato (Y)-793605. The meteorite has the lowest carbon abundance of any martian meteorite so far analysed. Once terrestrial contamination has been removed, Y79 contains only 7.3 ppm carbon with a δ^C∿-19‰. Carbon can be divided into four separate components, identified on the basis of combustion temperature and isotopic composition : (1) carbonates (possibly calcite; 1.2 ppm with δ^C∿-23‰); (2) magmatic carbon (1 ppm; δ^C∿-35±10‰); (3) martian atmospheric species and (4) cosmogenic carbon. The last three components can also be recognised in terms of their calculated nitrogen isotopic compositions. The isotopically-light carbonate in Y79 conforms to the observations made on other shergottites, that these meteorites have not been altered by surficial fluids in contact with the martian atmosphere, but rather contain carbonates produced from primary magmatic fluids. Neon and argon data were acquired simultaneously with nitrogen, but the small temperature increments selected for the analysis (to maximise information from the nitrogen experiment) resulted in low quantities of the noble gases being released, amounts close to that of the system blank. Only ^Ne yielded an abundance (2.2×10^cm^3 g^ STP) much higher than the blank, concentrations which, on the basis of their ^Ne/^Ne and ^Ne/^Ne ratios were found to be a 9 : 1 mix of cosmogenic neon with terrestrial atmospheric neon (from the blank). The approximate ^Ne exposure age of Y79 is ∿4 Myr, slightly higher than values for other lherzolitic shergottites

Amphibole: A major carrier of helium isotopes in crustal rocks

The first evidence for a specific role of amphiboles in He isotope balance of crustal rocks was presented in early contributions by Gerling et al. (1971, 1976). Since then it was shown that 4He and 3He concentrations in amphiboles generally exceed those in the host rock samples. Recently amphibole was considered as an important carrier of noble gases and other volatiles components in the course of their subduction into the mantle. This paper presents new data on the balance and mobility of noble gas isotopes and major gas constituents in amphibole separates in order to understand sources and evolution of volatile components of 2666 Ma old alkaline granites from Ponoy massif (Kola Peninsula), which underwent metamorphism 1802 Ma ago.In the amphiboles 3He, 4He and 40Ar* were dominantly produced in situ due to radioactive decay of the parent isotopes and associated nuclear reactions. A small fraction of He (≈ 3% of the total) is liberated by crushing and shows 3He/4He ratio indistinguishable from that found by total extraction. The fraction of trapped 40Ar* amounts to ≈ 40%; both these fractions presumably occupy fluid inclusions and show rather low 4He/40Ar* ≈ 0.1, a factor of ≈ 150 below the production ratio (calculated assuming no loss / gain of the species has happened since the time of metamorphism).3He has been better preserved in amphiboles compared with 4He: the retention parameter (measured amount of He / totally produced amount) for 3He (≈ 0.4) exceeds that for 4He (≈ 0.15).He extraction by fast and slow linear heating of amphiboles resulted in different release patterns. The fast heating (within 12 to 40 °C min− 1) revealed a superposition of two peaks. When heating with slower heating rate (below 8 °C min− 1) was applied, the high-temperature peak disappeared (the “disappearing site”). Extractions of He atoms from grain and powder samples at different heating rates have shown that: (1) the “disappearing site” is revealed by the fast heating analyses of different amphibole samples but not only those from the Ponoy massif; (2) amount of He liberated from the “disappearing site” is variable and generally much less than the total amount of He in the sample; (3) analysis of the powder produced in the crushing experiments never reveals the “disappearing site”; the temperature of He release from the powder is lower than that from the mm grain size sample by ≈ 50 °C. Possible explanations of the nature of the “disappearing site” are discussed. However, independently on nature of this effect, repeated gas extractions by heating at different rates would give additional information about structure and its transformation during heating of amphiboles.The simplest explanation of the observed abundances of noble gas isotopes in the amphibole separates from Ponoy granites suggests local production, redistribution and partial loss of noble gases during evolution of the massif

Simultaneous analysis of abundance and isotopic composition of nitrogen, carbon, and noble gases in lunar basalts: insights into interior and surface processes on the Moon

Simultaneous static-mode mass spectrometric measurements of nitrogen, carbon, helium, neon, and argon extracted from the same aliquot of sample by high-resolution stepped combustion have been made for a suite of six lunar basalts. Collecting abundance and isotopic data for several elements simultaneously from the same sample aliquot enables more detailed identification of different volatile components present in the basalts by comparing release patterns for volatiles across a range of temperature steps. This approach has yielded new data, from which new insights can be gained regarding the indigenous volatile inventory of the Moon. By taking into account N and C data for mid-temperature steps, unaffected by terrestrial contamination or cosmogenic additions, it is possible to determine the indigenous N and C signatures of the lunar basalts. With an average δ15N value of around +0.35‰, the indigenous N component seen in these samples is similar within error to other (albeit limited in number) isotopic measurements of indigenous lunar N. Average C/N ratios for indigenous volatiles in these six basalt samples are much lower than those of the terrestrial depleted mantle, or bulk silicate Earth, possibly suggesting much less C in the lunar interior, relative to N, than on Earth. Cosmogenic isotopes in these samples are well-correlated with published sample exposure ages, and record the rate of in situ production of spallogenic volatiles within material on the lunar surface

Predominantly Non-Solar Origin of Nitrogen in Lunar Soils

Simultaneous static-mode mass spectrometric measurements of nitrogen, carbon, helium, neon, and argon, extracted from the same aliquot of sample by high-resolution stepped combustion, have been made for a suite of five lunar soils. Noble gas isotope ratios show that the majority of noble gases are derived from a solar wind source; for example, at peak release temperatures of 500–600 °C,21Ne/22Ne = 0.0313 ± 0.0007 to 0.0333 ± 0.0007, and 20Ne/22Ne = 11.48 ± 0.05 to 12.43 ± 0.07, with values at the lowest temperature steps less fractionated during implantation from, and therefore even closer to, solar values (21Ne/22NeSW = 0.03361 ± 0.00018 and 20Ne/22NeSW = 14.001 ± 0.042 (Pepin et al., 2012)). Despite the co-release of nitrogen and solar wind argon, measured nitrogen isotopic signatures at each temperature step, whilst variable, are significantly more enriched in 15N compared to the measured solar wind nitrogen value from the Genesis mission. Therefore, mixing between a 15N-enriched non-solar planetary nitrogen source with solar wind nitrogen is required to explain the measured isotopic values from the stepped combustion analysis of lunar soils. Binary mixing calculations, made under different assumptions about the degree of loss of solar wind 36Ar, reveal that the majority (up to 98%) of the nitrogen released is derived from a non-solar source. The range of modelled non-solar end-member nitrogen compositions required to satisfy the measuredδ15N values varies between samples and temperature steps from +5‰ up to +300‰, or between +87‰ and +160‰ for bulk samples. This range of modelled isotopic compositions for the non-solar source of nitrogen encompasses measured values for several different groups of carbonaceous chondrite, as well as IDPs

Astrophysical significance of asymptotic giant branch Stellar wind energies recorded in meteoritic SiC grains

Using model calculations for ion implantation into spherical grains in free space, we have identified two noble gas components implanted with high and low energies into presolar SiC grains isolated from the Murchison meteorite. The low-energy component seems to be associated with the stellar winds of expanding asymptotic giant branch (AGB) stars during the main stage of their evolution. In contrast, the high-energy component was probably generated during the late, thermally pulsing peak of AGB evolution and was implanted into SiC grains as a high-speed, post-AGB wind during the planetary nebula formation stage. If true, this is the first time that such a planetary nebular component has been identified in the laboratory and provides astrophysics with a new arena of research possibilities. Possible involvement of chemically active elements in the implantation events established for noble gases is also discussed. Although we have concentrated on evidence provided by the implantation of noble gases, we also extend the discussions to chemically active elements such as Ba and Sr

Separation of planetary noble gas carrier from bulk carbon in enstatite chondrites during stepped combustion

The exact location of planetary noble gases in meteorites remains unknown but it is inferred to be closely associated with, if not precisely some portion of, the macromolecular organic material in carbonaceous chondrites . Herein we show that for enstatite chondrites the major carbonaceous component is not the carrier of the gases. This may also be true for other chondritic groups. Rather, these gases are all contained in a minor combustible constituent. This situation has all the hallmarks of a Russian matryoshka doll problem, as was witnessed previously in the study of meteorites prior to the understanding of the presence of presolar grains. A possible conclusion, which is in line with previous suggestions , is that planetary noble gases are also presolar and located in a new, and as yet unidentified, form of presolar material