Solar System Value Research Articles

The ESO SupJup Survey V: exploring atmospheric variability and orbit of the super-Jupiter AB Pictoris b with CRIRES+

ABSTRACT A growing number of directly-imaged companions have been recently characterized, with robust constraints on carbon-to-oxygen ratios and even isotopic ratios. Many companions and isolated targets have also shown spectral variability. In this work, we observed the super-Jupiter AB Pictoris b across four consecutive nights using VLT/CRIRES+ as part of the ESO SupJup survey, exploring how the constraints on chemical composition and temperature profile change over time using spectral line shape variations between nights. We performed atmospheric retrievals of the high-resolution observations and found broadly consistent results across all four nights, but there were differences for some parameters. We clearly detect H$_2$O, $^{12}$CO, and $^{13}$CO in each night, but abundances varied by ${\sim} 2\sigma$, which was correlated to the deep atmosphere temperature profiles. We also found differences in the $^{12}$C$/^{13}$C ratios in each night by up to ${\sim} 3\sigma$, which seemed to be correlated with the cloud deck pressure. Our combined retrieval simultaneously analysing all nights together constrained broadly the average of each night individually, with the C/O$=0.59\pm 0.01$, consistent with solar composition, and $^{12}$C$/^{13}$C $= 102\pm 8$, slightly higher than the Interstellar Medium (ISM) and Solar System values. We also find a low projected rotational velocity, suggesting that AB Pictoris b is either intrinsically a slow rotator due to its young age or that the spin axis is observed pole-on with a ${\sim} 90^\circ$ misalignment with its orbit inclination. Future observations will be able to further explore the variability and orbit of AB Pictoris b as well as for other companions.

Measuring the 34S and 33S Isotopic Ratios of Volatile Sulfur during Planet Formation

Stable isotopic ratios constitute powerful tools for unraveling the thermal and irradiation history of volatiles. In particular, we can use our knowledge of the isotopic fractionation processes active during the various stages of star, disk, and planet formation to infer the origins of different volatiles with measured isotopic patterns in our own solar system. Observations of planet-forming disks with the Atacama Large Millimeter/submillimeter Array (ALMA) now readily detect the heavier isotopologues of C, O, and N, while the isotopologue abundances and isotopic fractionation mechanisms of sulfur species are less well understood. Using ALMA observations of the SO and SO2 isotopologues in the nearby, molecule-rich disk around the young star Oph-IRS 48 we present the first constraints on the combined 32S/34S and 32S/33S isotope ratios in a planet-forming disk. Given that these isotopologues likely originate in relatively warm gas (>50 K), like most other Oph-IRS 48 volatiles, SO is depleted in heavy sulfur, while SO2 is enriched compared to solar system values. However, we cannot completely rule out a cooler gas reservoir, which would put the SO sulfur ratios more in line with comets and other solar system bodies. We also constrain the S18O/SO ratio and find the limit to be consistent with solar system values given a temperature of 60 K. Together these observations show that we should not assume solar isotopic values for disk sulfur reservoirs, but additional observations are needed to determine the chemical origin of the abundant SO in this disk, inform on what isotopic fractionation mechanism(s) are at play, and aid in unraveling the history of the sulfur budget during the different stages of planet formation.

Isotopic evidence of long-lived volcanism on Io.

Jupiter's moon Io hosts extensive volcanism, driven by tidal heating. The isotopic composition of Io's inventory of volatile chemical elements, including sulfur and chlorine, reflects its outgassing and mass loss history, and thus records information about its evolution. We used millimeter observations of Io's atmosphere to measure sulfur isotopes in gaseous SO2 and SO, and chlorine isotopes in gaseous NaCl and KCl. We find 34S/32S = 0.0595 ± 0.0038 (equivalent to δ34S = +347 ± 86‰), which is highly enriched compared to average Solar System values and indicates that Io has lost 94 to 99% of its available sulfur. Our measurement of 37Cl/35Cl = 0.403 ± 0.028 (δ37Cl = +263 ± 88‰) shows that chlorine is similarly enriched. These results indicate that Io has been volcanically active for most (or all) of its history, with potentially higher outgassing and mass-loss rates at earlier times.

Measurement of D/H and 13C/12C ratios in methane ice on Eris and Makemake: Evidence for internal activity

James Webb Space Telescope's NIRSpec infrared imaging spectrometer observed the outer solar system dwarf planets Eris and Makemake in reflected sunlight at wavelengths spanning 1 through 5 μm. Both objects have high albedo surfaces that are rich in methane ice, with a texture that permits long optical path lengths through the ice for solar photons. There is evidence for N2 ice absorption around 4.2 μm on Eris, though not on Makemake. No CO ice absorption is seen at 4.67 μm on either body. For the first time, absorption bands of two heavy isotopologues of methane are observed at 2.615 μm (13CH4), 4.33 μm (12CH3D), and 4.57 μm (12CH3D). These bands enable us to measure D/H ratios of (2.5 ± 0.5) × 10−4 and (2.9 ± 0.6) × 10−4, along with 13C/12C ratios of 0.012 ± 0.002 and 0.010 ± 0.003 in the surface methane ices of Eris and Makemake, respectively. The measured D/H ratios are much lower than that of presumably primordial methane in comet 67P/Churyumov-Gerasimenko, but they are similar to D/H ratios in water in many comets and larger outer solar system objects. This similarity suggests that the hydrogen atoms in methane on Eris and Makemake originated from water, indicative of geochemical processes in past or even ongoing hot environments in their deep interiors. The 13C/12C ratios are consistent with commonly observed solar system values, suggesting no substantial enrichment in 13C as could happen if the methane currently on their surfaces was the residue of a much larger inventory that had mostly been lost to space. Possible explanations include geologically recent outgassing from the interiors as well as processes that cycle the surface methane inventory to keep the uppermost surfaces refreshed.

SOLIS

Context. Recent results in astrochemistry have revealed that some molecules, such as interstellar complex organic species and deuterated species, can serve as valuable tools in the investigation of star-forming regions. Sulphuretted species can also be used to follow the chemical evolution of the early stages of a Sun-like star formation process. Aims. The goal is to obtain a census of S-bearing species using interferometric images towards SVS13-A, a Class I object associated with a hot corino that is rich in interstellar complex organic molecules. Methods. To this end, we used the NGC 1333 SVS13-A data at 3 mm and 1.4 mm obtained with the IRAM-NOEMA interferometer in the framework of the SOLIS (Seeds of Life in Space) Large Program. The line emission of S-bearing species was imaged and analyzed using local thermodynamic equilibrium (LTE) and large velocity gradient (LVG) approaches. Results. We imaged the spatial distribution on ≤300 au scale of the line emission of 32SO, 34SO, C32S, C34S, C33S, OCS, H2C32S, H2C34S, and NS. The low excitation (9 K) 32SO line traces: (i) the low-velocity SVS13-A outflow and (ii) the fast (up to 100 km s−1 away from the systemic velocity) collimated jet driven by the nearby SVS13-B Class 0 object. Conversely, the rest of the lines are confined in the inner SVS13-A region, where complex organics were previously imaged. More specifically, the non-LTE LVG analysis of SO, SO2, and H2CS indicates a hot corino origin (size in the 60–120 au range). Temperatures between 50 K and 300 K, as well as volume densities larger than 105 cm−3 have been derived. The abundances of the sulphuretted are in the following ranges: 0.3–6 × 10−6 (CS), 7 × 10−9–1 × 10−7 (SO), 1–10 × 10−7 (SO2), a few 10−10 (H2CS and OCS), and 10−10–10−9 (NS). The N(NS)/N(NS+) ratio is larger than 10, supporting the assessment that the NS+ ion is mainly formed in the extended envelope. Conclusions. The [H2CS]/[H2CO] ratio, once measured at high-spatial resolutions, increases with time (from Class 0 to Class II objects) by more than one order of magnitude (from ≤10−2 to a few 10−1). This suggests that [S]/[O] changes along the process of Sun-like star formation. Finally, the estimate of the [S]/[H] budget in SVS13-A is 2–17% of the Solar System value (1.8 × 10−5), which is consistent with what was previously measured towards Class 0 objects (1–8%). This finding supports the notion that the enrichment of the sulphuretted species with respect to dark clouds remains constant from the Class 0 to the Class I stages of low-mass star formation. The present findings stress the importance of investigating the chemistry of star-forming regions using large observational surveys as well as sampling regions on the scale of the Solar System.

Solar and wind grid system value in the United States: The effect of transmission congestion, generation profiles, and curtailment

<h2>Summary</h2> The value of electricity generated from wind and solar sources declines as supply increases. This decline in value has varied over time and across regions, indicating that strategies to mitigate value decline will need to be carefully targeted. To help guide development of these strategies, we empirically determine wind and solar value at ∼2,100 plants within United States wholesale markets by using local prices and plant-specific generation profiles. We determine how each plant loses (or gains) value because of its output profile, transmission congestion, and curtailment. In regions where wind or solar account for roughly 20% of electricity generation, its value is 30% to 40% below the regional average value of a flat output profile at all plants. Solar value reductions are most sensitive to output profile and wind value reductions are sensitive to both profile and congestion, region dependent. Curtailment was not a major source of value reduction.

Solar PV System Performance Ratio Evaluation for Electric Vehicles Charging Stations in Transit Oriented Development (TOD) Areas

Transit Oriented Development (TOD) areas are locations that have limited land area. Solar PV systems are planned to be installed in these areas to support electric vehicles such as e-scooters, electric cars, motorcycles, and buses. However, solar PV systems in general require a large land area. The purpose of this paper is to find out and compare the Performance Ratios (PR) of a solar PV system installed on the rooftop with a floating solar PV system installed on the lake to determine which solar PV system fits better for TOD areas. PR analysis uses two methods, PVSyst software simulation and is validated using mathematical calculations. The result of the PR of floating solar PV is 76.39% using PVSyst simulation and 80.24% using mathematical calculation. Meanwhile, the PR of rooftop solar PV is 82.69% using PVSyst simulation and 73.41% using mathematical calculation. The significant factors that influence PR value are the energy produced by the solar PV system, its losses, and albedo value of the reflector surface for bifacial solar PV. Albedo value has to be maximized in order to obtain a higher performance ratio value. Based on this study, both rooftop and floating PV systems are equally suitable for TOD areas.

The infrared view of dust and molecules around V4334 Sgr (Sakurai’s object): a 20-yr retrospective

ABSTRACT We present an analysis of the evolution of circumstellar dust and molecules in the environment of the very late thermal pulse object V4334 Sgr (Sakurai’s object) over an ∼20-yr period, drawing on ground-, airborne-, and space-based infrared photometry and spectroscopy. The dust emission, which started in 1997, resembles a blackbody that cooled from ∼1200 K in 1998 August to ∼180 K in 2016 July. The dust mass, assuming amorphous carbon, was ∼5 × 10−10 M⊙ in 1998 August, and we estimate that the total dust mass was ∼2 × 10−5 M⊙ by ∼2016. The appearance of a near-infrared excess in 2008 suggests that a new episode of (or renewed) mass-loss began then. We infer lower limits on the bolometric luminosity of the embedded star from that of the dust shell, which rose to ∼16 000 L⊙ before declining to ∼3000 L⊙. There is evidence for weak 6–7 μm absorption, which we attribute to hydrogenated amorphous carbon formed in material ejected by Sakurai’s object during a mass ejection phase that preceded the 1997 event. We detect small hydrocarbon and other molecules in the spectra, and trace the column densities in hydrogen cyanide (HCN) and acetylene (C2H2). We use the former to determine the 12C/13C ratio to be 6.4 ± 0.7, 14 times smaller than the Solar system value.

Connections Between Nuclear Physics and the Origin of Life - Examining the Origin of Biomolecular Chirality

The discovery of bio-molecules in meteorites with an excess of one chiral state has created one of the biggest questions in astrobiology today. That is, what is the origin of bio-molecular homochirality? Studies of this question are highly interdisciplinary, and while several phenomenological models exist, we examine the relationship between fundamental symmetries at the particle level and the macroscopic formation of bio-molecules. A model has been developed which couples fundamental interactions with the formation of molecular chirality. In this magneto-chiral model atomic nuclei bound in amino acids interact via the weak interaction in stellar environments. Nuclei are coupled to the molecular geometry (chirality) via the shielding tensor, the same interaction responsible for NMR identification. Associated with this is the fact that isotopic abundances vary from solar system values. Interactions with leptons can selectively destroy one chiral state over the other while changing isotopic values. Possible sites are proposed in which this model may exist.

Isotopic Fractionation in 3He-rich SEP Events

A well established characteristic of 3He-rich solar energetic particle events is a pattern of abundance enhancements relative to normal solar system values that increase approximately monotonically with atomic number (or mass), leading to enhancements that can exceed 100× for the heaviest elements relative to oxygen. In a 2018 paper, Mason and Klecker (M&K) suggested that the heavy element enhancements could be due to characteristics of the stopping powers of low-energy nuclei penetrating thin layers of H gas or plasma. We present results of a new calculation of enhancements in a H gas and show them to be in reasonable agreement with the M&K results. Studies of heavy-element isotopic composition in 3He-rich events using data from ACE/SIS have also shown that heavier isotopes of an element typically exhibit significant abundance enhancements relative to lighter isotopes of the same element. We applied the new calculation to investigate whether the observed isotopic fractionation can be explained using the M&K H-gas model with the same parameters that account for the heavy-element abundances and found that the measured isotopic enhancements are significantly greater than the predicted values. A search of a larger parameter space was also not able to reconcile the elemental and isotopic enhancement values. However, this search did reveal trends in the dependence on the model parameters that merit further investigation.

Investigation of Mass Transfer with Different Models in a Solar Energy Food-Drying System

In drying systems, the examination of the drying rate values of the food product in advance gives important information about the raw material to be dried. In this study, thin-layer drying behavior of apple slices in a convective solar dryer was investigated. The experiments were carried out at a drying air temperature of 46–63 °C and a drying air speed of 0.7–1.8 m/s. In order to determine the drying kinetics, the mass change of apple slices was recorded under all drying air conditions. The effects of drying air temperature and speed, drying speed of apple slices, dimensionless moisture content, were investigated. In a solar drying system, thermal efficiency, solar radiation and air velocity values were measured. The drying kinetics of 15-mm thick apple slices were examined for three days in the solar drying system. Using the decision tree algorithm, which is a machine learning algorithm, a predictive model was created for moisture rate in drying experiments and four linear equations were obtained. According to obtained equations, the collector in the drying system depends on the inlet–outlet temperature values, the drying room inlet–outlet temperature values, the drying room humidity values and air velocity values. Moisture rate data were applied to twelve different models and their performance was determined by root mean square error (RMSE) analysis. The mathematical model with the least error rate was (RMSE: 0.09) Midilli model. A comparison was made between these drying models in the literature and the model generated by the decision tree algorithm. According to the results of RMSE error analysis, it was shown that the model created with the decision tree algorithm predicted the moisture rate values with less error values RMSE: 0.03) than the Midilli model.

Instabilities in the Early Solar System due to a Self-gravitating Disk.

Modern studies of the early solar system routinely invoke the possibility of an orbital instability among the giant planets triggered by gravitational interactions between the planets and a massive exterior disk of planetesimals. Previous works have suggested that this instability can be substantially delayed (~100s Myr) after the formation of the giant planets. Bodies in the disk are typically treated in a semi-active manner, wherein their gravitational force on the planets is included, but interactions between the planetesimals are ignored. We perform N-body numerical simulations using GENGA, which makes use of GPUs to allow for the inclusion of all gravitational interactions between bodies. Although our simulated Kuiper belt particles are more massive than the probable masses of real primordial Kuiper belt objects, our simulations indicate that the self-stirring of the primordial Kuiper belt is very important to the dynamics of the giant planet instability. We find that interactions between planetesimals dynamically heat the disk and typically prevent the outer solar system instability from being delayed by more than a few tens of million years after giant planet formation. Longer delays occur in a small fraction of systems that have at least 3.5 AU gaps between the planets and planetesimal disk. Our final planetary configurations match the solar system at a rate consistent with other previous works in most regards. Pre-instability heating of the disk typically yields final Jovian eccentricities comparable to the modern solar system value, which has been a difficult constraint to match in past works.

A Large-scale Survey of CO and Its Isotopologues toward the Rosette Molecular Cloud

Using the PMO-13.7m millimeter telescope at Delingha in China, we have conducted a large-scale simultaneous survey of $^{12}$CO, $^{13}$CO, and C$^{18}$O J=1-0 emission toward the Rosette molecular cloud (RMC) region with a sky coverage of 3.5 $\times$ 2.5 deg$^2$. The majority of the emission in the region comes from the RMC complex with velocities lying in the range from -2 km s$^{-1}$ to 20.5 km s$^{-1}$. Beyond this velocity range, 73 molecular clumps are identified with kinematic distances from 2.4 kpc to 11 kpc. Based on the spatial and velocity distribution, nine individual clouds, C1-C9, have been identified for the RMC complex. It appears that the C3 cloud is different from other clouds in the RMC complex in view of its characteristic velocity, excitation temperature, and velocity dispersion. Most of the young stellar clusters in the region are located in positions of both high column density and high excitation temperature. Seven new molecular filaments are discovered in the RMC complex. Evidence for cloud-cloud collision is found in the region of young stellar clusters REFL9 and PouF, showing that these young stellar clusters probably result from a cloud-cloud collision. The abundance ratios of $^{13}$CO to C$^{18}$O in the region have a mean value of 13.7 which is 2.5 times larger than the solar system value, showing that UV photons from the nearby OB clusters have strong influence on the chemistry of clouds in the RMC complex.

Halogens as tracers of protosolar nebula material in comet 67P/Churyumov–Gerasimenko

We report the first in situ detection of halogens in a cometary coma, that of 67P/Churyumov-Gerasimenko. Neutral gas mass spectra collected by the European Space Agencys Rosetta spacecraft during four periods of interest from the first comet encounter up to perihelion indicate that the main halogen-bearing compounds are HF, HCl and HBr. The bulk elemental abundances relative to oxygen are ∼8.9 × 10 −5 for F/O, ∼1.2 × 10 −4 for Cl/O, and ∼2.5 × 10 −6 for Br/O, for the volatile fraction of the comet. The cometary isotopic ratios for 37 Cl/ 35 Cl and 81 Br/ 79 Br match the solar system values within the error margins. The observations point to an origin of the hydrogen halides in molecular cloud chemistry, with frozen hydrogen halides on dust grains, and a subsequent incorporation into comets as the cloud condensed and the solar system formed.

Origin of nanodiamonds from Allende constrained by statistical analysis of C isotopes from small clusters of acid residue by NanoSIMS

Meteoritic nanodiamonds carry noble gases with anomalies in their stable isotopes that have drawn attention to their potentially presolar origin. Measurements of 12C/13C isotope ratios of presolar nanodiamonds are essential to understanding their origins, but bulk studies do not show notable deviations from the solar system 12C/13C ratio.We implemented a technique using secondary ion mass spectrometry with maximized spatial resolution to measure carbon isotopes in the smallest clusters of nanodiamonds possible. We measured C and Si from clusters containing as few as 1000 nanodiamonds, the smallest clusters of nanodiamonds measured to date by traditional mass spectrometry. This allowed us to investigate many possible complex compositions of the nanodiamonds, both through direct methods and statistical analysis of the distributions of observed isotopic ratios.Analysis of the breadth of distributions of carbon isotopic ratios for a number of ∼1000-nanodiamond aggregates indicates that the 12C/13C ratio may be drawn from multiple Gaussian distributions about different isotopic ratios, which implies the presence of presolar material. The mean isotopic ratio is consistent with the solar system value, so presolar components are required to be either low in concentration, or to have a mean ratio close to that of the solar system. Supernovae are likely candidates for the source of such a presolar component, although asymptotic giant branch stars are not excluded.A few aggregates show deviations from the mean 12C/13C ratio large enough to be borderline detections of enrichments in 13C. These could be caused by the presence of a small population of nanodiamonds formed from sources that produce extremely 13C-rich material, such as J-stars, novae, born-again asymptotic giant branch stars, or supernovae. Of these possible sources, only supernovae would account for the anomalous noble gases carried in the nanodiamonds.

Training and integrating rural women into technology: a study of Renewable Energy Technology in Bangladesh

Women in developing countries are often poorly integrated into new technology sectors, but technical and vocational training may be a means of empowering women to achieve such integration. This article addresses the challenges of integrating rural women in Bangladesh into the Solar Home System (SHS) value chain through training. It reviews a USAID-funded training project undertaken by Grameen Shakti (GS), a major Renewable Energy Technology (RET) enterprise in Bangladesh, and examines the outcomes for the rural women involved in the project. Over the period 2005–2010, the company trained 2797 rural women at an extensive network of rural technology centres. While GS reached its target of selling and installing one million SHS units throughout the country, it was less successful in integrating women trainees into the value chain, employing less than 3% of women trainees after training. These women employees assembled SHS components, but their jobs did not draw on their acquired skills in promotion, installation, and maintenance of the SHS. Of those not employed at GS, a proportion found income-generating activities elsewhere and felt they benefited from the training. This study reviews the training, gender segmentation in the value chain, and changes in technology and markets to help explain this outcome. Both cultural barriers and limits to project planning, monitoring, and implementation affected the outcome. Moreover, initiatives based on small-scale, village-level production appear vulnerable to mass production and rapidly changing market conditions.

In situ isotopic studies of the U-depleted Allende CAI Curious Marie: Pre-accretionary alteration and the co-existence of 26Al and 36Cl in the early solar nebula

The isotopic composition of oxygen as well as 26Al-26Mg and 36Cl-36S systematics were studied in Curious Marie, an aqueously altered Allende CAI characterized by a Group II REE pattern and a large 235U excess produced by the decay of short-lived 247Cm. Oxygen isotopic compositions in the secondary minerals of Curious Marie follow a mass-dependent fractionation line with a relatively homogenous depletion in 16O (Δ17O of −8‰) compared to unaltered minerals of CAI components. Both Mg and S show large excesses of radiogenic isotopes (26Mg∗ and 36S∗) that are uniformly distributed within the CAI, independent of parent/daughter ratio. A model initial 26Al/27Al ratio [(6.2±0.9)×10−5], calculated using the bulk Al/Mg ratio and the uniform δ26Mg∗∼+43‰, is similar to the canonical initial solar system value within error. The exceptionally high bulk Al/Mg ratio of this CAI (∼95) compared to other inclusions is presumably due to Mg mobilization by fluids. Therefore, the model initial 26Al/27Al ratio of this CAI implies not only the early condensation of the CAI precursor but also that aqueous alteration occurred early, when 26Al was still at or near the canonical value. This alteration event is most likely responsible for the U depletion in Curious Marie and occurred at most 50kyr after CAI formation, leading to a revised estimate of the early solar system 247Cm/235U ratio of (5.6±0.3)×10−5. The Mg isotopic composition in Curious Marie was subsequently homogenized by closed-system thermal processing without contamination by chondritic Mg. The large, homogeneous 36S excesses (Δ36S∗∼+97‰) detected in the secondary phases of Curious Marie are attributed to 36Cl decay (t1/2=0.3Myr) that was introduced by Cl-rich fluids during the aqueous alteration event that led to sodalite formation. A model 36Cl/35Cl ratio of (2.3±0.6)×10−5 is calculated at the time of aqueous alteration, translating into an initial 36Cl/35Cl ratio of ∼1.7–3×10−5 at solar system birth. The Mg and S radiogenic excesses suggest that 26Al and 36Cl co-existed in the early solar nebula, raising the possibility that, in addition to an irradiation origin, 36Cl could have also been derived from a stellar source.

A Low Abundance of 135Cs in the Early Solar System from Barium Isotopic Signatures of Volatile-depleted Meteorites

Abstract Precise knowledge of the abundances of short-lived radionuclides at the start of the solar system leads to fundamental information about the stellar environment of solar system formation. Previous investigations of the short-lived system (t 1/2 = 2.3 Ma) have resulted in a range of calculated initial amounts of 135Cs, with most estimates elevated to a level that requires extraneous input of material to the protoplanetary disk. Such an array of proposed 135Cs/133Cs initial solar system values has severely restricted the system’s use as both a possible chronometer and as an informant about supernovae input. However, if 135Cs was as abundant in the early solar system as previously proposed, the resulting deficits in its daughter product 135Ba would be easily detectable in volatile-depleted parent bodies (i.e., having sub-chondritic Cs/Ba) from the very early solar system. In this work, we show that angrites and eucrites, which were volatile-depleted within ∼1 million years of the start of the solar system, do not possess deficits in 135Ba compared to other planetary bodies. From this, we calculate an upper limit for the initial 135Cs/133Cs of 2.8 × 10−6, well below previous estimates. This significantly lower initial 135Cs/133Cs ratio now suggests that all of the 135Cs present in the early solar system was inherited simply from galactic chemical evolution and no longer requires an addition from an external stellar source such as an asymptotic giant branch star or SN II, corroborating evidence from several other short-lived radionuclides.

High precision Al–Mg systematics of forsterite-bearing Type B CAIs from CV3 chondrites

In order to further elucidate possible temporal relationships between different varieties of calcium-, aluminum-rich inclusions (CAIs), we measured the aluminum–magnesium isotopic systematics of seven examples of the rare type known as forsterite-bearing Type B (FoB) inclusions from four different CV3 carbonaceous chondrites: Allende, Efremovka, NWA 3118, and Vigarano. The primary phases (forsterite, Al–Ti-rich diopside, spinel, melilite, and anorthite) in each inclusion were analyzed in situ using high-precision secondary ion mass-spectrometry (SIMS). In all cases, minerals with low Al/Mg ratios (all except anorthite) yield well-defined internal Al–Mg isochrons, with a range of initial 26Al/27Al ratios [(26Al/27Al)0] ranging from (5.30±0.22)×10−5 down to (4.17±0.43)×10−5. Anorthite in all cases is significantly disturbed relative to the isochrons defined by the other phases in the same CAIs, and in several cases contains no resolved excesses of radiogenic 26Mg (δ26Mg∗) even at 27Al/24Mg ratios greater than 1000. The fact that some FoBs preserve (26Al/27Al)0 of ∼5.2×10−5, close to the canonical value of (5.23±0.13)×10−5 inferred from bulk magnesium-isotope measurements of CV CAIs (B. Jacobsen et al., 2008), demonstrates that FoBs began forming very early, contemporaneous with other more-refractory CAIs. The range of (26Al/27Al)0 values further shows that FoBs continued to be reprocessed over ∼200,000years of nebular history, consistent with results obtained for other types of igneous CAIs in CV chondrites. The absence of any correlation between of CAI+FoB formation or reprocessing times with bulk composition or CAI type means that there is no temporal evolutionary sequence between the diverse CAI types. The initial δ26Mg∗ value in the most primitive FoB (SJ101) is significantly lower than the canonical solar system value of −0.040±0.029‰.

Extreme early solar system chemical fractionation recorded by alkali-rich clasts contained in ordinary chondrite breccias

New K–Ca and Rb–Sr isotopic analyses have been performed on alkali-rich igneous rock fragments in the Yamato (Y)-74442 and Bhola LL-chondritic breccias to better understand the extent and timing of alkali enrichments in the early solar system. The Y-74442 fragments yield a K–Ca age of 4.41±0.28 Ga for λ(40K)=0.5543 Ga−1 with an initial 40Ca/44Ca ratio of 47.1618±0.0032. Studying the same fragments with the Rb–Sr isotope system yields an age of 4.420±0.031 Ga for λ(87Rb)=0.01402 Ga−1 with an initial ratio of 87Sr/86Sr=0.7203±0.0044. An igneous rock fragment contained in Bhola shows a similar alkali fractionation pattern to those of Y-74442 fragments but does not plot on the K–Ca or Rb–Sr isochron of the Y-74442 fragments. Calcium isotopic compositions of whole-rock samples of angrite and chondrites are primordial, indistinguishable from mantle-derived terrestrial rocks, and here considered to represent the initial composition of bulk silicate Earth. The initial ε40Ca value determined for the source of the alkali clasts in Y-74442 that is ∼0.5 ε-units higher than the solar system value implies an early alkali enrichment.Multi-isotopic studies on these alkali-rich fragments reveal that the source material of Y-74442 fragments had elemental ratios of K/Ca=0.43±0.18, Rb/Sr=3.45±0.66 and K/Rb∼170, that may have formed from mixtures of an alkali-rich component (possibly an alkali-enriched gaseous reservoir produced by fractionation of early nebular condensates) and chondritic components that were flash-heated during an impact event on the LL-chondrite parent body ∼4.42 Ga ago. Further enrichments of potassium and rubidium relative to calcium and strontium as well as a mutual alkali-fractionation (K/Rb∼50 and heavier alkali-enrichment) would have likely occurred during subsequent cooling and differentiation of this melt. Alkali fragments in Bhola might have undergone similar solid–vapor fractionation processes to those of Y-74442 fragments but appear to have formed via a distinct impact melting event.