¹James M. D. Day,¹Jennifer Maria‐Benavides,²Francis M. McCubbin,²Ryan A. Zeigler
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13074]
¹Scripps Institution of Oceanography, University of California San Diego, , California, USA
²NASA Johnson Space Center, Houston, Texas, USA
Published by arrangement with John Wiley & Sons

Curation and preparation of samples for chemical analysis can occasionally lead to significant contamination. This issue is of concern in the study of lunar samples, especially those from the Apollo sample collection, where available masses are finite. Here we present compositional data for stainless steels that have commonly been used in the processing of Apollo lunar samples at NASA Johnson Space Center, including a chisel and a vessel typically used to transfer Apollo samples to principal investigators. The Type 304 stainless steels are Cr‐rich, with high concentrations of Mn (4000–18,000 μg g⁻¹), Cu (1000–22,900 μg g⁻¹), Mo (1030–1120 μg g⁻¹), and W (72–193 μg g⁻¹). They have elevated highly siderophile element (HSE) concentrations (up to 92 ng g⁻¹ Os), ¹⁸⁷Os/¹⁸⁸Os ranging from 0.1310 to 0.1336, and negligible lithophile element abundances. We find that, while metal contamination is possible, significant (≫0.01% by mass) addition of stainless steel is required to strongly affect the composition of the HSE, W, Mo, Cr, or Cu for most Apollo lunar samples. Nonetheless, careful appraisal on a case‐by‐case basis should take place to ensure contamination introduced through sample processing during curation is at acceptably low levels. A survey of lunar mare basalts and crustal rocks indicates that metal contamination plays a negligible role in the compositional variability of the HSE and W compositions preserved in these samples. Further work to constrain contamination for other properties of Apollo samples is required (e.g., organics, microbes, water, noble gases, and magnetics), but the effect of metal contamination can be well‐constrained for the Apollo lunar collection.

¹N. G. Rudraswami,¹D. Fernandes,¹A. K. Naik,¹M. Shyam Prasad,²S. Taylor
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13068]
¹National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa, India
²Cold Regions Research and Engineering Laboratory, , Hanover, New Hampshire, USA
Published by arrangement with John Wiley & Sons

The scoriaceous cosmic spherules (CSs) that make up to a few percent (for sizes >150 μm size) of total micrometeorite flux are ubiquitous and have remained enigmatic. The present work provides in‐depth study of 81 scoriaceous CSs, from observed ~4000 CSs, collected from Antarctica (South Pole water well) and deep‐sea sediments (Indian Ocean) that will allow us to analyze the nature of these particles. The fine‐grained texture and the chemical composition of scoriaceous particles suggest that they are formed from matrix materials that are enriched in volatiles. The volatile components such as water, sulfide, Na, K, etc. have vanished due to partial evaporation and degassing during Earth’s atmospheric entry leaving behind the vesicular features, yet largely preserving the elemental composition. The elemental ratios (Ca/Si, Mg/Si, Al/Si, Fe/Si, and Ni/Si) of interplanetary dust particles (IDPs) are compatible with the scoriaceous CSs, which in turn are indistinguishable from the matrices of CI and CM chondrites signifying similarities in the nature of the sources. Furthermore, the texture of cometary particles bears resemblance to the texture of the scoriaceous particles. The compilation of petrographic texture, chemical, and trace element composition of scoriaceous CSs presents a strong case for matrix components from hydrated and volatile‐rich bodies, such as CI and CM chondrites, rather than chondrules. We conclude that the fine‐grained scoriaceous CSs, the matrix materials of hydrated chondrites, IDPs, and cometary particles that overlap compositionally were widespread, indicating a dominant component in the early solar nebula.

¹I. Leya,²J. Masarik,³Y. Lin
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13070]
¹Space Science and Planetology, University of Bern, Bern, Switzerland
²Department of Nuclear Physics, Comenius University, Bratislava, Slovakia
³Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

Using new model calculations, we study the production of chlorine and sulfur isotopes in different irradiation scenarios. We demonstrate that irradiation during meteorite transit from the asteroid belt to Earth has a negligible influence on the sulfur isotopic composition. We analyzed five different physical assemblages: carbonaceous chondrites, carbonaceous chondrites covered with water ice, carbonaceous chondrites covered with water ice that contains silicates and chlorine, precursor CAIs, and water ice that contains chlorine. For each of these five we ran simulations in which they were irradiated by galactic cosmic rays or solar energetic particles. We found that for producing sufficient amounts of 36Cl, the required GCR and SEP flux densities must have been either unreasonably high on absolute terms or must had been high relatively late after the formation of the solar system. This finding casts doubt on the interpretation of the correlation lines in the diagram 36S/34S and 35Cl/34S as isochrons. Alternatively, the correlation may be interpreted as mixing between water that contains chlorine that has been irradiated (likely as ice) either by GCR or SEP particles and sulfur (without any chlorine) with solar isotopic composition. Using this model we can explain the correlation as mixing between components, one of which was exposed to energetic particles; the conditions of this irradiation are not unrealistic.