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Abstract
Elucidating the role of sulfur on the structure of silicate glasses and melts at elevated pressures and temperatures is important for understanding transport properties, such as electrical conductivity and viscosity, of magma oceans and mantle-derived melts. These properties are fundamental to modeling the evolution of terrestrial planets and moons. Despite several investigations of sulfur speciation in glasses, questions remain regarding the effect of S on complex glasses at highly reducing conditions relevant to Mercury. Glasses were synthetized with compositions representative of the Northern Volcanic Plains of Mercury and containing quantities of S as high as 5 wt.%. Multiple spectroscopic methods and microprobe analyses were employed to probe the glasses, including in situ impedance spectroscopy at 2- and 4-GPa pressures and temperatures up to 1740 K using a multi-anvil press, 29Si NMR spectroscopy, and Raman spectroscopy. Electrical activation energies (Ea) in the glassy state range from 0.56 to 1.10 eV, in agreement with sodium as the main charge carrier. The electrical measurements suggest that sulfide improves Na+ transport and may overcome a known impeding effect of the divalent cation Ca2+. The glass transition temperature lies between 700-750 K, and for temperatures up to 970 K Ea decreases (0.35-0.68 eV) and the conductivities of the samples converge (~5-8 *10-3 S/m). At Tquench, the melt fraction is 50-70% and melt conductivity varies from 0.7 to 2.2 S/m, with the sample containing 5 wt.% S the most conductive among the set. 29Si NMR spectra reveal that a high fraction of S bonds with Si in these complex glasses, an important insight that has not been recognized previously. Raman spectra and maps reveal regions rich in Ca-S or Mg-S bonds. The evidence of sulfide interactions with both Si and Ca/Mg suggest that alkaline earth sulfides can be considered weak network modifiers in these glasses, under highly reduced conditions. Experimental data from impedance spectroscopy, NMR spectroscopy, Raman spectroscopy and electron microprobe analyses. The description of the experiments and analyses is explained the manuscript. # Title of Dataset Data used in manuscript GCA-D-23-00571 entitled Experimental Investigation of the Bonding of Sulfur in Highly Reduced Silicate Glasses and Melts by A. Pommier, M. J. Tauber, H. Pirotte, G.D. Cody, A. Steele, E.S. Bullock, B. Charlier, and B.O. Mysen (Geochimica et Cosmochimica Acta). The spreadsheet lists all the measurements shown in the figures of the manuscript. Each tab correspond to a figure: -Figures 2 and 3: electron microprobe analyses. -Figures 4 and 5: impedance spectroscopy -Figure 6: NMR spectroscopy -Figures 8 and 9: Raman spectroscopy -Figure 10: NBO/T estimates The reader is referred to the manuscript for details about the experimental procedures and results. ## Description of the data and file structure * Figure 2 tab: Each sample name starts with BBC. For each sample, electron microprobe analyses are shown for traverses across the sample and the content of each oxide is in wt.%. * Figure 3 tab: Microprobe traverse in sample BBC16. The content of each oxide is in wt.%. * Figure 4: Impedance spectra of samples BBC13 and BBC17 at selected temperatures. For each temperature, the different columns correspond to the frequency, time, real component (Z') and imaginary component (Z"). * Figure 5 tab: electrical resistance (R) and conductivity (EC) of different samples as a function of temperature (T). Each sample name starts with BBC. For each sample, the different columns correspond to temperature (in degC and K), inverse T, resistance, conductivity and Ln (conductivity). * Figure 6: NMR spectra for four starting glasses (VT48, 52, 53, 54). The first column is the chemical shift, and the other columns correspond to the intensity of each sample. * Figure 7: Raman spectrum of starting glass VT55. The first column is the Raman shift, and the second column corresponds to the intensity of the sample. * Figure 8: Raman spectra of sulfide components in starting glass VT52 and samples from experiments BBC17 and BBC18. For each sample, the first column is the Raman shift, and the second column corresponds to the intensity of the sample. Copyright: CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
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Abstract
Sulfur plays a major role in martian geochemistry and sulfate minerals are important repositories of water. However, their hydration states on Mars are poorly constrained. Therefore, understanding the hydration and distribution of sulfate minerals on Mars is important for understanding its geologic, hydrologic, and atmospheric evolution as well as its habitability potential. NASA's Perseverance rover is currently exploring the Noachian-age Jezero crater, which hosts a fan-delta system associated with a paleolake. The crater floor includes two igneous units (the Seitah and Maaz formations), both of which contain evidence of later alteration by fluids including sulfate minerals. Results from the rover instruments Scanning Habitable Environments with Raman and Luminescence for Organics and Chemistry and Planetary Instrument for X-ray Lithochemistry reveal the presence of a mix of crystalline and amorphous hydrated Mg-sulfate minerals (both MgSO4 center dot[3-5]H2O and possible MgSO4 center dot H2O), and anhydrous Ca-sulfate minerals. The sulfate phases within each outcrop may have formed from single or multiple episodes of water activity, although several depositional events seem likely for the different units in the crater floor. Textural and chemical evidence suggest that the sulfate minerals most likely precipitated from a low temperature sulfate-rich fluid of moderate pH. The identification of approximately four waters puts a lower constraint on the hydration state of sulfate minerals in the shallow subsurface, which has implications for the martian hydrological budget. These sulfate minerals are key samples for future Mars sample return.
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Abstract
Chloroflexus sp. MS-CIW-1 was isolated from a phototrophic mat in Mushroom Spring, an alkaline hot spring in Yellowstone National Park, WY, USA. We report the draft genome of 4.8 Mb consisting of 6 contigs with 3755 protein-coding genes and a GC content of 54.45%.
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Abstract
Mass coral bleaching is one of the clearest threats of climate change to the persistence of marine biodiversity. Despite the negative impacts of bleaching on coral health and survival, some corals may be able to rapidly adapt to warming ocean temperatures. Thus, a significant focus in coral research is identifying the genes and pathways underlying coral heat adaptation. Here, we review state-of-the-art methods that may enable the discovery of heat-adaptive loci in corals and identify four main knowledge gaps. To fill these gaps, we describe an experimental approach combining seascape genomics with CRISPR/Cas9 gene editing to discover and validate heat-adaptive loci. Finally, we discuss how information on adaptive genotypes could be used in coral reef conservation and management strategies.
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Abstract
Anaerobic digestion is a bioenergy technology that can play a vital role in achieving net-zero emissions by converting organic matter into biomethane and biogenic carbon dioxide. By implementing bioenergy with carbon capture and storage (BECCS), carbon dioxide can be separated from biomethane, captured, and permanently stored, thus generating carbon dioxide removal (CDR) to offset hard-to-abate emissions. Here, we quantify the global availability of waste biomass for BECCS and their CDR and biomethane technical potentials. These biomass feedstocks do not create additional impacts on land, water, and biodiversity and can allow a more sustainable development of BECCS while still preserving soil fertility. We find that up to 1.5 Gt CO2 per year, or 3% of global GHG emissions, are available to be deployed for CDR worldwide. The conversion of waste biomass can generate up to 10 700 TWh of bioenergy per year, equivalent to 10% of global final energy consumption and 27% of global natural gas supply. Our assessment quantifies the climate mitigation potential of waste biomass and its capacity to contribute to negative emissions without relying on extensive biomass plantations.
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Abstract
Trait differences between invasive plants and the plants in their recipient communities moderate the impact of invaders on community composition. Callery pear (Pyrus calleryana Decne.) is a fast-growing, stress-tolerant tree native to China that has been widely planted for its ornamental value. In recent decades, P. calleryana has naturalized throughout the eastern United States, where it spreads rapidly and achieves high abundance in early-successional environments. Here we compare the impacts of low-density, establishment-phase P. calleryana to those of functionally similar native trees on the understory community diversity and total cover of three early-successional meadows in Indiana's Eastern Corn Belt Plains. In contrast to our prediction that P. calleryana would have greater negative effects on the total abundance and diversity of the understory plant community compared with native tuliptree (Liriodendron tulipifera L.), American sycamore (Platanus occidentalis L.), or non-tree control plots, we found that these low-density populations of P. calleryana had no significant impact on total cover, species richness, or diversity indices for the understory community compared with the native trees and non-tree control plots. Likewise, the studied populations of P. calleryana had no significant impact on the native, introduced, woody, or native tree subsets of the understory community. These results indicate that in young, low-density populations situated in early-successional meadows, the trait differences between P. calleryana and functionally similar native trees are not of a great enough magnitude to produce changes in community composition. Going forward, complementary research on the impacts of P. calleryana on community composition and ecosystem processes in areas with long-established, dense invasions or invasions in more sensitive ecosystems would allow us to more fully understand how this widespread invader disrupts its host ecosystems.
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Abstract
We present a spectroscopic analysis of Eridanus IV (Eri IV) and Centaurus I (Cen I), two ultrafaint dwarf galaxies of the Milky Way. Using IMACS/Magellan spectroscopy, we identify 28 member stars of Eri IV and 34 member stars of Cen I. For Eri IV, we measure a systemic velocity of vsys=-31.5-1.2+1.3kms-1 , and velocity dispersion sigma v=6.1-0.9+1.2kms-1 . Additionally, we measure the metallicities of 16 member stars of Eri IV. We find a metallicity of [Fe/H]=-2.87-0.07+0.08 , and resolve a dispersion of sigma [Fe/H]=0.20 +/- 0.09. The mean metallicity is marginally lower than all other known ultrafaint dwarf galaxies, making it one of the most metal-poor galaxies discovered thus far. Eri IV also has a somewhat unusual right-skewed metallicity distribution. For Cen I, we find a velocity v sys = 44.9 +/- 0.8 km s-1, and velocity dispersion sigma v=4.2-0.5+0.6kms-1 . We measure the metallicities of 27 member stars of Cen I, and find a mean metallicity [Fe/H] = -2.57 +/- 0.08, and metallicity dispersion sigma[Fe/H]=0.38-0.05+0.07 . We calculate the systemic proper motion, orbit, and the astrophysical J-factor for each system, the latter of which indicates that Eri IV is a good target for indirect dark matter detection. We also find no strong evidence for tidal stripping of Cen I or Eri IV. Overall, our measurements confirm that Eri IV and Cen I are dark-matter-dominated galaxies with properties largely consistent with other known ultrafaint dwarf galaxies. The low metallicity, right-skewed metallicity distribution, and high J-factor make Eri IV an especially interesting candidate for further follow-up.
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Abstract
We present high-cadence ultraviolet through near-infrared observations of the Type Ia supernova (SN Ia) 2023bee at D = 32 +/- 3 Mpc, finding excess flux in the first days after explosion, particularly in our 10 minutes cadence TESS light curve and Swift UV data. Compared to a few other normal SNe Ia with early excess flux, the excess flux in SN 2023bee is redder in the UV and less luminous. We present optical spectra of SN 2023bee, including two spectra during the period where the flux excess is dominant. At this time, the spectra are similar to those of other SNe Ia but with weaker Si ii, C ii, and Ca ii absorption lines, perhaps because the excess flux creates a stronger continuum. We compare the data to several theoretical models on the origin of early excess flux in SNe Ia. Interaction with either the companion star or close-in circumstellar material is expected to produce a faster evolution than observed. Radioactive material in the outer layers of the ejecta, either from double detonation explosion or from a 56Ni clump near the surface, cannot fully reproduce the evolution either, likely due to the sensitivity of early UV observable to the treatment of the outer part of ejecta in simulation. We conclude that no current model can adequately explain the full set of observations. We find that a relatively large fraction of nearby, bright SNe Ia with high-cadence observations have some amount of excess flux within a few days of explosion. Considering potential asymmetric emission, the physical cause of this excess flux may be ubiquitous in normal SNe Ia.
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Thousands of galaxies flood this near-infrared image of galaxy cluster SMACS 0723. High-resolution imaging from NASA’s James Webb Space Telescope combined with a natural effect known as gravitational lensing made this finely detailed image possible. Credit: NASA, ESA, CSA, STScI
February 09, 2024
Feature Story

JWST is Alan Dressler’s dream come true

Henrique Marquez Reggiani at the Carnegie Observatories Open House
February 09, 2024
Spotlight

Postdoc Spotlight: Henrique Marquez Reggiani

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