Ice Band Research Articles

JWST Ice Band Profiles Reveal Mixed Ice Compositions in the HH 48 NE Disk

Planet formation is strongly influenced by the composition and distribution of volatiles within protoplanetary disks. With JWST, it is now possible to obtain direct observational constraints on disk ices, as recently demonstrated by the detection of ice absorption features toward the edge-on HH 48 NE disk as part of the Ice Age Early Release Science program. Here, we introduce a new radiative transfer modeling framework designed to retrieve the composition and mixing status of disk ices using their band profiles, and apply it to interpret the H2O, CO2, and CO ice bands observed toward the HH 48 NE disk. We show that the ices are largely present as mixtures, with strong evidence for CO trapping in both H2O and CO2 ice. The HH 48 NE disk ice composition (pure versus polar versus apolar fractions) is markedly different from earlier protostellar stages, implying thermal and/or chemical reprocessing during the formation or evolution of the disk. We infer low ice-phase C/O ratios around 0.1 throughout the disk, and also demonstrate that the mixing and entrapment of disk ices can dramatically affect the radial dependence of the C/O ratio. It is therefore imperative that realistic disk ice compositions are considered when comparing planetary compositions with potential formation scenarios, which will fortunately be possible for an increasing number of disks with JWST.

Analysis of the Antarctic Marginal Ice Zone Based on Unsupervised Classification of Standalone Sea Ice Model Data

AbstractThe Antarctic marginal ice zone, the regularly wave‐affected outer band of the sea ice covered Southern Ocean, typically contains an unconsolidated ice cover comprised of smaller, thinner floes than the inner ice pack. Thus, it is a highly dynamic region and susceptible to rapid expansion and contraction, making it a focal area for understanding and predicting the response of Antarctic sea ice to a changing climate. This novel study uses unsupervised statistical clustering of sea ice data simulated by a global sea ice model (standalone CICE6 combined with a wave propagation module and prescribed ocean) to address the outstanding challenge of separating the marginal ice zone from the inner ice pack in sea ice data sets. The method identifies a marginal ice zone with the desired characteristics and floe size is shown to be the key variable in the classification. Simulated marginal ice zone widths are similar to those derived from satellite observations of wave penetration distances, but contrast with those using the standard 15%–80% areal sea ice concentration proxy, particularly during austral winter. The simulated marginal ice zone is found to undergo a seasonal transition due to new ice formation in winter, increased drift in spring, and increased rates of wave‐induced breakup and melting in summer. The understanding gained from the study motivates incorporation of wave and floe‐scale processes in sea ice models, and the methods are available for application to outputs from high‐resolution and coupled sea ice–ocean–wave models for more detailed studies of the marginal ice zone (in both hemispheres).

JWST Reveals CO Ice, Concentrated CO2 Deposits, and Evidence for Carbonates Potentially Sourced from Ariel’s Interior

The Uranian moon Ariel exhibits a diversity of geologically young landforms, with a surface composition rich in CO2 ice. The origin of CO2 and other species, however, remains uncertain. We report observations of Ariel’s leading and trailing hemispheres, collected with NIRSpec (2.87–5.10 μm) on the James Webb Space Telescope. These data shed new light on Ariel's spectral properties, revealing a double-lobed CO2 ice scattering peak centered near 4.20 and 4.25 μm, with the 4.25 μm lobe possibly representing the largest CO2 Fresnel peak yet observed in the solar system. A prominent 4.38 μm 13CO2 ice feature is also present, as is a 4.90 μm band that results from 12CO2 ice. The spectra reveal a 4.67 μm 12CO ice band and a broad 4.02 μm band that might result from carbonate minerals. The data confirm that features associated with CO2 and CO are notably stronger on Ariel’s trailing hemisphere compared to its leading hemisphere. We compared the detected CO2 features to synthetic spectra of CO2 ice and mixtures of CO2 with CO, H2O, and amorphous carbon, finding that CO2 could be concentrated in deposits thicker than ∼10 mm on Ariel’s trailing hemisphere. Comparison to laboratory data indicates that CO is likely mixed with CO2. The evidence for thick CO2 ice deposits and the possible presence of carbonates on both hemispheres suggests that some carbon oxides could be sourced from Ariel’s interior, with their surface distributions modified by charged particle bombardment, sublimation, and seasonal migration of CO and CO2 from high to low latitudes.

Nuclear Quantum Effects on the Electronic Structure of Water and Ice.

The electronic properties and optical response of ice and water are intricately shaped by their molecular structure, including the quantum mechanical nature of the hydrogen atoms. Despite numerous previous studies, a comprehensive understanding of the nuclear quantum effects (NQEs) on the electronic structure of water and ice at finite temperatures remains elusive. Here, we utilize molecular simulations that harness efficient machine-learning potentials and many-body perturbation theory to assess how NQEs impact the electronic bands of water and hexagonal ice. By comparing path-integral and classical simulations, we find that NQEs lead to a larger renormalization of the fundamental gap of ice, compared to that of water, ultimately yielding similar bandgaps in the two systems, consistent with experimental estimates. Our calculations suggest that the increased quantum mechanical delocalization of protons in ice, relative to water, is a key factor leading to the enhancement of NQEs on the electronic structure of ice.

PROJECT-J: JWST Observations of HH46 IRS and Its Outflow. Overview and First Results

We present the first results of the JWST program PROJECT-J (PROtostellar JEts Cradle Tested with JWST), designed to study the Class I source HH46 IRS and its outflow through NIRSpec and MIRI spectroscopy (1.66–28 μm). The data provide line images (∼6.″6 in length with NIRSpec, and up to ∼20″ with MIRI) revealing unprecedented details within the jet, the molecular outflow, and the cavity. We detect, for the first time, the redshifted jet within ∼90 au from the source. Dozens of shock-excited forbidden lines are observed, including highly ionized species such as [Ne iii] 15.5 μm, suggesting that the gas is excited by high velocity (>80 km s−1) shocks in a relatively high-density medium. Images of H2 lines at different excitations outline a complex molecular flow, where a bright cavity, molecular shells, and a jet-driven bow shock interact with and are shaped by the ambient conditions. Additional NIRCam 2 μm images resolve the HH46 IRS ∼110 au binary system and suggest that the large asymmetries observed between the jet and the H2 wide-angle emission could be due to two separate outflows being driven by the two sources. The spectra of the unresolved binary show deep ice bands and plenty of gaseous lines in absorption, likely originating in a cold envelope or disk. In conclusion, JWST has unraveled for the first time the origin of the HH46 IRS complex outflow demonstrating its capability to investigate embedded regions around young stars, which remain elusive even at near-IR wavelengths.

JWST detections of amorphous and crystalline HDO ice toward massive protostars

Tracing the origin and evolution of interstellar water is key to understanding many of the physical and chemical processes involved in star and planet formation. Deuterium fractionation offers a window into the physicochemical history of water due to its sensitivity to local conditions. The aim of this work is to utilize the increased sensitivity and resolution of the James Webb Space Telescope (JWST) to quantify the HDO/H$_ $O ratio in ices toward young stellar objects (YSOs) and to determine if the HDO/H$_ $O ratios measured in the gas phase toward massive YSOs (MYSOs) are representative of the ratios in their ice envelopes. Two protostars observed in the Investigating Protostellar Accretion (IPA) program using JWST NIRSpec were analyzed: HOPS 370, an intermediate-mass YSO (IMYSO), and IRAS 20126+4104, a MYSO. The HDO ice toward these sources was quantified via its 4.1 mu m band. The contributions from the CH$_ $OH combination modes to the observed optical depth in this spectral region were constrained via the CH$_ $OH 3.53 mu m band to ensure that the integrated optical depth of the HDO feature was not overestimated. H$_ $O ice was quantified via its 3 mu m band. New laboratory IR spectra of ice mixtures containing HDO, H$_ $O, CH$_ $OH, and CO were collected to aid in the fitting and chemical interpretation of the observed spectra. HDO ice is detected above the 3sigma level in both sources. It requires a minimum of two components, one amorphous and one crystalline, to obtain satisfactory fits. The H$_ $O ice band at 3 mu m similarly requires both amorphous and crystalline components. The observed peak positions of the crystalline HDO component are consistent with those of annealed laboratory ices, which could be evidence of heating and subsequent recooling of the ice envelope (i.e., thermal cycling). The CH$_ $OH 3.53 mu m band is fit best with two cold components, one consisting of pure CH$_ $OH and the other of CH$_ $OH in an H$_ $O-rich mixture. From these fits, ice HDO/H$_ $O abundance ratios of 4.6pm 1.8times 10$^ $ and 2.6pm 1.2times 10$^ $ are obtained for HOPS 370 and IRAS 20126+4104, respectively. The simultaneous detections of both crystalline HDO and crystalline H$_ $O corroborate the assignment of the observed feature at 4.1 mu m to HDO ice. The ice HDO/H$_ $O ratios are similar to the highest reported gas HDO/H$_ $O ratios measured toward MYSOs and the hot inner regions of isolated low-mass protostars, suggesting that at least some of the gas HDO/H$_ $O ratios measured toward massive hot cores are representative of the HDO/H$_ $O ratios in ices. The need for an H$_ $O-rich CH$_ $OH component in the CH$_ $OH ice analysis supports recent experimental and observational results that indicate that some CH$_ $OH ice may form prior to the CO freeze-out stage in H$_ $O-rich ice layers.

JWST observations of 13CO2 ice

The structure and composition of simple ices can be severely modified during stellar evolution by protostellar heating. Key to understanding the involved processes are thermal and chemical tracers that can be used to diagnose the history and environment of the ice. The 15.2 µm bending mode of 12CO2 in particular has proven to be a valuable tracer of ice heating events but suffers from grain shape and size effects. A viable alternative tracer is the weaker 13CO2 isotopologue band at 4.39 µm, which has now become accessible at high S/N with the James Webb Space Telescope (JWST). In this study, we present JWST NIRSpec observations of 13CO2 ice in five deeply embedded Class 0 sources that span a wide range in masses and luminosities (0.2–104 L⊙) taken as part of the Investigating Protostellar Accretion Across the Mass Spectrum (IPA) program. The band profiles vary significantly depending on the source, with the most luminous sources showing a distinct narrow peak at 4.38 µm. We first applied a phenomenological approach with which we demonstrate that a minimum of three to four Gaussian profiles are needed to fit the absorption feature of 13CO2. We then combined these findings with laboratory data and show that a 15.2 µm 12CO2 bending-mode-inspired five-component decomposition can be applied to the isotopologue band, with each component representative of CO2 ice in a specific molecular environment. The final solution consists of cold mixtures of CO2 with CH3OH, H2O, and CO as well as segregated heated pure CO2 ice at 80 K. Our results are in agreement with previous studies of the 12CO2 ice band, further confirming that 13CO2 is a useful alternative tracer of protostellar heating and ice composition. We also propose an alternative solution consisting only of heated mixtures of CO2:CH3OH and CO2:H2O ices and warm pure CO2 ice at 80 K (i.e., no cold CO2 ices) for decomposing the ice profiles of HOPS 370 and IRAS 20126, the two most luminous sources in our sample that show strong evidence of ice heating resulting in ice segregation.

Cryoconite holes geomorphometry, spatial distribution and radiative impact over the Hells Gate Ice Shelf, East Antarctica

Abstract Cryoconite holes are structures characteristic of the glacierised ablation areas, formed from dark sediment deposition which melt the glacier ice leading to their cylindrical structure formation. The present study focuses on an unstudied blue ice area of East Antarctica over the Hells Gate Ice Shelf in Northern Victoria Land. Taking advantage of neural network methodology applied on drone acquisitions, an automatic detection of cryoconite holes was carried out (88% of accuracy), mapping ~3500 m2 (0.4% fractional cover) of cryoconite holes over an area of 900 000 m2. The surveyed area showed heterogeneity in cryoconite hole distribution, with some regions showing an area fraction of holes (regions exhibiting frozen ponds and ice bands) as high as 8%. Thanks to this detection, the spatially integrated radiative forcing of cryoconite holes over blue ice surface was estimated to be almost 1 Wm−2. This estimation was based on the measured albedo difference between the two surfaces, which averages 0.31. However, the radiative forcing is strongly increased if calculated at a single cryoconite hole scale, showing an average of ~200 Wm−2. In conclusion, the present research represents a first attempt of analysing cryoconite holes as factors impacting the blue ice in Northern Victoria Land, deepening our understanding of their glaciological role at the margins of the East Antarctic Ice Sheet.

Theoretical investigations of the vibrational spectra and hydrogen bond vibrations of two-dimensional ice I

In 2020, experimental observations of a stable two-dimensional (2D) ice I structure on a gold substrate were reported. As an atomic-level material, 2D ice has potential applications in many fields. However, the vibrational spectra of 2D ice I, including its infrared (IR) absorption, Raman scattering, and inelastic neutron-scattering spectra, have not been collected, owing to the complexity of the experimental conditions required to do so. We used first-principle density functional theory calculations to model 2D ice I and proved that it can stably exist without a gold substrate. We also simulated the vibrational phonon density of states and the IR and Raman spectra of 2D ice I. The vibrational frequencies in the translational band of 2D ice I were lower than those of 3D ice, owing to the hydrogen bonds of the former being weaker than those of the latter. The dynamic process analysis of hydrogen bonds showed that the vibrational modes of 2D ice I are quite different with that of 3D ice showing a different vibrational spectrum.

Applying q-Gaussians to the OH-stretching Raman bands of Water and Ice

Applying q-Gaussians to the OH-stretching Raman bands of Water and Ice

The Galaxy Activity, Torus, and Outflow Survey (GATOS)

We use JWST/MIRI MRS spectroscopy of a sample of six local obscured type 1.9/2 active galactic nuclei (AGN) to compare their nuclear mid-IR absorption bands with the level of nuclear obscuration traced by X-rays. This study is the first to use subarcsecond angular resolution data of local obscured AGN to investigate the nuclear mid-IR absorption bands with a wide wavelength coverage (4.9–28.1 μm). All the nuclei show the 9.7 μm silicate band in absorption. We compare the strength of the 9.7 and 18 μm silicate features with torus model predictions. The observed silicate features are generally well explained by clumpy and smooth torus models. We report the detection of the 6 μm dirty water ice band (i.e., a mix of water and other molecules such as CO and CO2) at subarcsecond scales (∼0.26″ at 6 μm; inner ∼50 pc) in a sample of local AGN with different levels of nuclear obscuration in the range log NHX-Ray (cm−2)∼22 − 25. We find good correlation between the 6 μm water ice optical depths and NHX-Ray. This result indicates that the water ice absorption might be a reliable tracer of the nuclear intrinsic obscuration in AGN. The weak water ice absorption in less obscured AGN (log NHX-ray (cm−2)≲23.0 cm−2) might be related to the hotter dust temperature (> TsubH2O ∼ 110 K) expected to be reached in the outer layers of the torus due to their more inhomogeneous medium. Our results suggest it might be necessary to include the molecular content, such as H2O, aliphatic hydrocarbons (CH−), and more complex polycyclic aromatic hydrocarbon (PAH) molecules, in torus models to better constrain key parameters such as the torus covering factor (i.e., nuclear obscuration).

JWST Reveals Widespread CO Ice and Gas Absorption in the Galactic Center Cloud G0.253+0.016

We report JWST NIRCam observations of G0.253+0.016, the molecular cloud in the Central Molecular Zone known as “The Brick,” with the F182M, F187N, F212N, F410M, F405N, and F466N filters. We catalog 56,146 stars detected in all six filters using the crowdsource package. Stars within and behind The Brick exhibit prodigious absorption in the F466N filter that is produced by a combination of CO ice and gas. In support of this conclusion, and as a general resource, we present models of CO gas and ice and CO2 ice in the F466N, F470N, and F410M filters. Both CO gas and ice contribute to the observed stellar colors. We show, however, that CO gas does not absorb the Pfβ and Huϵ lines in F466N, but that these lines show excess absorption, indicating that CO ice is present and contributes to observed F466N absorption. The most strongly absorbed stars in F466N are extincted by ∼2 mag, corresponding to >80% flux loss. This high observed absorption requires very high column densities of CO, and thus a total CO column that is in tension with standard CO abundance and/or gas-to-dust ratios. This result suggests the CO/H2 ratio and dust-to-gas ratio are greater in the Galactic Center than in the Galactic disk. Ice and/or gas absorption is observed even in the cloud outskirts, implying that additional caution is needed when interpreting stellar photometry in filters that overlap with ice bands throughout galactic centers.

Applying DRIFT Spectroscopy for High Temperature Electrochemical Cells-Lessons from SMOX Based Gas Sensors

In operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, the metal oxide sample is illuminated by the infrared beam, and the scattered (rather than transmitted) light is collected with appropriate optics for analysis. In addition to being better suited for operando methods, DRIFT spectroscopy has also been found to be more surface sensitive than other IR techniques suitable for powder samples, such as TIRS, ATR-IRS, and PM-IRRAS.(Roedel et al., 2008) DRIFT spectroscopy has allowed for significant gains in understanding the surface chemistry of semiconducting metal oxide (SMOX) based sensors to be made.Despite the potential usefulness in unravelling different surface mechanisms, ranging from the influence of humidity on the oxygen reduction reaction in fuel cell cathodes to insights about the anodic coking mechanisms when using hydrocarbon fuels, the use of DRIFTs for metal oxide electrochemical cells is still in its infancy, with only a handful of near operando studies being reported. (Cumming et al., 2015; Hauser et al., 2020; Tezel et al., 2022) One critical consideration is the potentially problematic intrinsic IR radiation of samples and the limited stability of cell materials at the high relevant operation temperatures. Nonetheless, using clever cooling systems that prevent the windows from overheating and intricate cell designs to allow for separate oxygen and fuel supply, Cumming et al. and more recently Hauser et al. were able to measure DRIFT spectra at elevated temperatures on cells. (Cumming et al., 2015; Hauser et al., 2020) In both cases, DRIFT spectra were depicted up to 600 ˚C without reports of significant errors due to radiation stemming from the sample. As a result, it is promising that through further optimization, DRIFT spectroscopy could become a useful tool for studying metal oxide based electrochemical systems.For the further optimization, lessons learned during the development of operando cells for SMOX based gases sensors are pertinent. Here a way forward for the optimization will be presented. Starting with practical aspects of DRIFT spectroscopy, e.g. need for precisely controlled room environments in non-evacuated systems or increased signal intensity through window optimization. Common artefacts will be shown, and avoidance strategies will be shown, e.g. ice bands that can be removed through detector evacuation. Additional considerations that are relevant specifically when working with metals oxides will be reviewed and the advantages of selecting the referencing method of Olinger and Griffiths over the traditionally used Kubelka-Munk will be elaborated.(Cumming et al., 2015; Jill M Olinger & Peter R Griffiths, 1988) The usefulness of using isotopically labelled gases to differentiate surface species, e.g. separate metal-oxygen groups from metal-hydroxides, will be discussed. Finally, the potential pitfalls of comparing different samples quantitatively will be highlighted. Overall, this presentation will provide a useful guideline for the future design of an operando DRIFT chamber for oxide based electrochemical cells.BibliographyCumming, D. J., Tumilson, C., Taylor, S. F. R., Chansai, S., Call, A. v., Jacquemin, J., Hardacre, C., & Elder, R. H. (2015). Development of a diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) cell for the in situ analysis of co-electrolysis in a solid oxide cell. Faraday Discussions, 182, 97–111. https://doi.org/10.1039/c5fd00030kHauser, D., Nenning, A., Opitz, A. K., Klötzer, B., & Penner, S. (2020). Spectro-electrochemical setup for in situ and operando mechanistic studies on metal oxide electrode surfaces. Review of Scientific Instruments, 91(8). https://doi.org/10.1063/5.0007435Jill M Olinger, & Peter R Griffiths. (1988). Quantitative effects of an Absorbing Matrix on Near-Infrared Diffuse Reflectance Spectra. Anal. Chem., 60(21), 2427–2435.Roedel, E., Urakawa, A., Kureti, S., & Baiker, A. (2008). On the local sensitivity of different IR techniques: Ba species relevant in NOx storage-reduction. Physical Chemistry Chemical Physics, 10(40), 6190–6198. https://doi.org/10.1039/b808529cTezel, E., Guo, D., Whitten, A., Yarema, G., Freire, M., Denecke, R., McEwen, J.-S., & Nikolla, E. (2022). Elucidating the Role of B-Site Cations toward CO2 Reduction in Perovskite-Based Solid Oxide Electrolysis Cells . Journal of The Electrochemical Society, 169(3), 034532. https://doi.org/10.1149/1945-7111/ac5e9b

Chemical and visual characterisation of EGRIP glacial ice and cloudy bands within

Abstract. Impurities in polar ice play a critical role in ice flow, deformation, and the integrity of the ice core record. Especially cloudy bands, visible layers with high impurity concentrations, are prominent features in ice from glacial periods. Their physical and chemical properties are poorly understood, highlighting the need to analyse them in more detail. We bridge the gap between decimetre and micrometre scales by combining the visual stratigraphy line scanner, fabric analyser, microstructure mapping, Raman spectroscopy, and laser ablation inductively coupled plasma mass spectrometry 2D impurity imaging. We classified approximately 1300 cloudy bands from glacial ice from the East Greenland Ice-core Project (EGRIP) ice core into seven different types. We determine the localisation and mineralogy of more than 1000 micro-inclusions at 13 depths. The majority of the minerals found are related to terrestrial dust, such as quartz, feldspar, mica, and hematite. We further found carbonaceous particles, dolomite, and gypsum in high abundance. Rutile, anatase, epidote, titanite, and grossular are infrequently observed. The 2D impurity imaging at 20 µm resolution revealed that cloudy bands are clearly distinguishable in the chemical data. Na, Mg, and Sr are mainly present at grain boundaries, whereas dust-related analytes, such as Al, Fe, and Ti, are located in the grain interior, forming clusters of insoluble impurities. We present novel vast micrometre-resolution insights into cloudy bands and describe the differences within and outside these bands. Combining the visual and chemical data results in new insights into the formation of different cloudy band types and could be the starting point for future in-depth studies on impurity signal integrity and internal deformation in deep polar ice cores.

Two Forms of Ice Identified in Mars-like Clay Using Neutron Spectroscopy

The capacity of clay minerals to store large amounts of water is utilized in a number of industrial and environmental applications on Earth, for example, as components in geosynthetic clay liners in landfills or ingredients in water-based drilling fluids, and could prove important on Mars to identify future human landing sites where water could be harvested. The subzero behavior of water interacting within the interlayer space of clay minerals is of particular interest in most applications but remains poorly understood. To better understand the hydrothermal mechanism by which water ice bonds and separates from clay interlayers, we have utilized neutron spectroscopy, spectral analysis, and phonon band assignment. The inelastic neutron scattering from sodium montmorillonite, hydrated at 24, 73, and 166% water content, as well as an oven-dried sample, were measured to assess the vibrational density of states. The water contents studied provide a range of pore dimensions within clay gels that have varying degrees of confinement. The type of ice formed from water held in larger intra- and interparticle pores differs substantially from that confined within the interlayer (pseudo-two-layer hydrate), and the differences vary with hydration level. Spectral subtraction over an energy transfer range 50 < E < 550 cm–1 (8 < E < 70 meV) produces clearly two different forms of ice: hexagonal and cubic in the two wetter samples. A form of interfacial ice, presumably of a lower density, is observed in the vibrational density of states spectrum of the sample hydrated to a pseudo-two-layer hydrate (ie 24% gravimetric water content (GWC), 10 H2O/Na+). No hexagonal or cubic ice is observed in this sample. The four vibrational modes within the translation band of hexagonal ice are apparent within the sample hydrated to 166% gravimetric water content, in which pores greater than 20 nm are largely water-filled. By considering hydrogen bonding of the water to the clay surface, our data indicate an increase in the strength of the H-bond due to a shorter distance to the hydroxyl. We attribute this decrease to the pores in the clay generating a localized negative pressure or “suction” effect, thus attracting the water.

Survey of Ices toward Massive Young Stellar Objects. I. OCS, CO, OCN−, and CH3OH

An important tracer of the origin and evolution of cometary ices is the comparison with ices found in dense clouds and toward young stellar objects (YSOs). We present a survey of ices in the 2–5 μm spectra of 23 massive YSOs, taken with the NASA InfraRed Telescope Facility SpeX spectrometer. The 4.90 μm absorption band of OCS ice is detected in 20 sight lines, more than 5 times the previously known detections. The absorption profile shows little variation and is consistent with OCS embedded in CH3OH-rich ices, and proton-irradiated H2S or SO2-containing ices. The OCS column densities correlate well with those of CH3OH and OCN−, but not with H2O and apolar CO ice. This association of OCS with CH3OH and OCN− firmly establishes their formation location deep inside dense clouds or protostellar envelopes. The median composition of this ice phase toward massive YSOs, as a percentage of H2O, is CO:CH3OH:OCN−:OCS = 24:20:1.53:0.15. CS, due to its low abundance, is likely not the main precursor to OCS. Sulfurization of CO is likely needed, although the source of this sulfur is not well constrained. Compared to massive YSOs, low-mass YSOs and dense clouds have similar or somewhat lower CO and CH3OH ice abundances, but less OCN− and more apolar CO, while OCS awaits detection. Comets tend to be underabundant in carbon-bearing species, but this does not appear to be the case for OCS, perhaps signalling OCS production in protoplanetary disks.

Probing the surface environment of large T-type asteroids

Context. The thermal and radiative environments encountered by asteroids have shaped their surface features. Recent observations have focused on asteroids in the main belt and showed indications for ices and organics in the interiors of the asteroids that were likely significant on prebiotic Earth. They stand out in reflectance spectra as darker, redder colours than most colocated asteroids. Aims. We probe the surface environment of large (&gt;80km in diameter) T-type asteroids. This taxonomic type is relatively ill-constrained as an independent group. We discuss their place of origin based on our probing. Methods. We performed spectroscopic observations of two T-type asteroids, (96) Aegle and (570) Kythera, over the L band (2.8–4.0 µm) using the Subaru telescope. The spectra of other T-type asteroids are available in the literature, as are survey datasets. Based on this, we strove to find commonalities and global trends in this group. We also used the archival polarimetric data of the asteroids and meteorite spectra from laboratory experiments to constrain their surface texture and composition. Results. Our targets exhibit red L-band continuum slopes, (0.30±0.04) µm−1 for (96) Aegle and (0.31 ± 0.03) µm−1 for (570) Kythera, that are similar to those of (1) Ceres and 67P/Churyumov-Gerasimenko, and have an OH-absorption feature with band centres &lt;2.8 µm. For (96) Aegle, we find an indication of a shallow N–H band near 3.1 µm and a C–H band of organic materials over 3.4–3.6 µm, whereas no diagnostic bands of water ice and other volatiles exceeding the noise of the data were seen for both asteroids. The large T-type asteroids except for (596) Scheila display spectral shapes similar to those of to our targets. About 50% of large T-type asteroids contain an absorption band near 0.6−0.65 µm that is likely associated with hydrated minerals. For T-type asteroids (except for Jupiter Trojans) of all sizes, we found a weak correlation that the smaller the diameter and the closer to the Sun, the redder the visible (0.5−0.8 µm) slope. Conclusions. The 2.9 µm band depths of large T-type asteroids suggest that they might have experienced aqueous alteration comparable to Ch-type asteroids, but that it was more intense than for most of the main-belt asteroids. The polarimetric phase curve of the T-type asteroids is well described by a particular surface structure. The 0.5−4.0 µm reflectance spectra of large T-type asteroids appear most similar to those of CI chondrites with grain sizes of ~25−35 µm. Taken as a whole, we propose that large T-type asteroids may have been dislodged roughly around 10 au in the early Solar System.

Influence of grain growth on CO2 ice spectroscopic profiles

Context. Interstellar dust grain growth in dense clouds and protoplanetary disks, even when moderate, affects the observed interstellar ice profiles as soon as a significant fraction of dust grains are in the size range close to the wave vector at the considered wavelength. The continuum baseline correction made prior to analysing ice profiles influences the subsequent analysis and hence the estimated ice composition, which are typically obtained by band fitting using thin film ice mixture spectra. Aims. We explore the effect of grain growth on the spectroscopic profiles of ice mantle constituents, focusing particularly on carbon dioxide, with the aim of understanding how it can affect interstellar ice mantle spectral analysis and interpretation. Methods. Using the discrete dipole approximation for scattering and absorption of light, the mass absorption coefficients of several distributions of grains – composed of ellipsoidal silicate cores with water and carbon dioxide ice mantles – are calculated. A few models also include amorphous carbon in the core and pure carbon monoxide in the ice mantle. We explore the evolution of the size distribution starting in the dense core phase in order to simulate the first steps of grain growth up to three microns in size. The resulting mass absorption coefficients are injected into RADMC-3D radiative transfer models of spherical dense core and protoplanetary disk templates to retrieve the observable spectral energy distributions. Calculations are performed using the full scattering capabilities of the radiative transfer code. We then focus on the particularly relevant calculated profile of the carbon dioxide ice band at 4.27 µm. Results. The carbon dioxide anti-symmetric stretching mode profile is a meaningful indicator of grain growth. The observed profiles towards dense cores obtained with the Infrared Space Observatory and Akari satellites already show profiles possibly indicative of moderate grain growth. Conclusions. The observation of true protoplanetary disks at high inclination with the James Webb Space Telescope should present distorted profiles that will allow constraints to be placed on the extent of dust growth. The more evolved the dust size distribution, the more the extraction of the ice mantle composition will require both understanding and taking grain growth into account.

On the origin of molecular oxygen on the surface of Ganymede

Since its first identification on the surface of Ganymede in 1995, molecular oxygen (O2) ice has been at the center of a scientific debate as the surface temperature of the Jovian moon is on average well above the freezing point of O2. Laboratory evidence suggested that solid O2 may either exist in a cold (<50 K) subsurface layer of the icy surface of Ganymede, or it is in an atmospheric haze of the moon. Alternatively, O2 is constantly replenished at the surface through ion irradiation of water-containing ices. A conclusive answer on the existence of solid O2 on the surface of Ganymede is hampered by the lack of detailed, extensive observational datasets. We present new ground-based, high-resolution spectroscopic observations of Ganymede's surface obtained at the Telescopio Nazionale Galileo. These are combined with dedicated laboratory measurements of ultraviolet-visible (UV–vis) photoabsorption spectra of O2 ice, both pure and mixed with other species of potential interest for the Galilean satellites. Our study confirms that the two bands identified in the visible spectra of Ganymede's surface are due to the (1,0) and (0,0) transition bands of O2 ice. Oxygen-rich ice mixtures including water (H2O) and carbon dioxide (CO2) can reproduce observational reflectance data of the Ganymede's surface better than pure O2 ice in the temperature range 20–35 K. Solid H2O and CO2 also provide an environment where O2 ice can be trapped at higher temperatures than its pure ice desorption under vacuum space conditions. Our experiments at different temperatures show also that the (1,0)/(0,0) ratio in case of the CO2:O2 = 1:2 ice mixture at 35 K has the closest value to observations, while at 30 K the (1,0)/(0,0) ratio seems to be mixture independent with the exception of the N2:O2 = 1:2 ice mixture. The present work will be part of a laboratory spectroscopic database in support of the ESA/JUICE mission to the Jovian system.

Longitudinal Variation of H2O Ice Absorption on Miranda

Many tidally locked icy satellites in the outer solar system show leading/trailing hemispherical asymmetries in the strength of near-infrared (NIR) H2O ice absorption bands, in which the absorption bands are stronger on the leading hemisphere. This is often attributed to a combination of magnetospheric irradiation effects and impact gardening, which can modify grain size, expose fresh ice, and produce dark contaminating compounds that reduce the strength of absorption features. Previous research identified this leading/trailing asymmetry on the four largest classical Uranian satellites but did not find a clear leading/trailing asymmetry on Miranda, the smallest and innermost classical moon. We undertook an extensive observational campaign to investigate variations of the NIR spectral signature of H2O ice with longitude on Miranda’s northern hemisphere. We acquired 22 new spectra with the TripleSpec spectrograph on the ARC 3.5 m telescope and four new spectra with GNIRS on Gemini North. Our analysis also includes three unpublished and seven previously published spectra taken with SpeX on the 3 m IRTF. We confirm that Miranda has no substantial leading/trailing hemispherical asymmetry in the strength of its H2O ice absorption features. We additionally find evidence for an anti-Uranus/sub-Uranus asymmetry in the strength of the 1.5 μm H2O ice band that is not seen on the other Uranian satellites, suggesting that additional endogenic or exogenic processes influence the longitudinal distribution of H2O ice band strengths on Miranda.