Linking asteroids and meteorites to the primordial planetesimal population

Meteorites provide a unique insight into early Solar System processes. However, to fully interpret this record requires that these meteorites are related back to their source asteroids and ultimately to the original planetesimal population that formed early in Solar System history. As a first step in this process an assessment has been undertaken of the likely number of distinct source asteroids sampled by meteorites and related extraterrestrial materials. The results of this survey indicate that there are between 95 and 148 parent bodies represented in our sample collections. This number has been steadily increasing as new “anomalous” meteorites are characterized. Attempts to link these parent bodies to identified asteroidal sources has so far been of limited success, due to the non-unique reflectance spectra of almost all known asteroids. Asteroid (4) Vesta and the HEDs (howardites, eucrite, diogenite) meteorites is the best example of a relatively non-disputed asteroid-meteorite linkage. As part of this study the “parent body” concept has been examined and it is found to be a widely, but loosely, used term in the literature to designate “a body that supplies meteorites to Earth.” This concept could be rendered more meaningful by discriminating between primary and secondary parent bodies. A primary parent body is the source asteroid from which the meteorite is ultimately derived, and a secondary parent body is an asteroid derived through impact or break-up of the primary body. A clear example of this usage is provided by (4) Vesta, with the main asteroid being the primary parent body and the Vestoids representing secondary parent bodies. The concept of primary vs. secondary parent bodies may have important implications for early Solar System evolution. Chondritic parent bodies are known to have accreted between 1 and 4 Myr after CAIs. This timing difference may reflect the fact that their source asteroids, particularly those of the carbonaceous chondrites, are secondary bodies, with the original CAI-bearing primary bodies destroyed during early collisional processing. The number of primary parent bodies represented by meteorites (95 to 148) appears low when compared to the estimated number of asteroids in the main belt (> 100,000 with diameters exceeding ∼2 km). A range of potential reasons may explain this apparent mismatch: i) meteorites provide an unrepresentative sampling of the main belt, ii) the belt may only contain a limited number of primary parent bodies, iii) meteorites may be preferentially derived from the ∼120 identified asteroid families, iv) loosely consolidated types are filtered by Earth’s atmosphere, v) multiple, near-identical, “clone” parent bodies may be present in the belt. At present, it is not possible to determine which of these potential mechanisms are dominant and all may be operating to a greater or lesser extent. Based on classical accretion models the meteorite record appears to be highly unrepresentative of the primordial asteroid population. In contrast, pebble accretion models suggest that these first-generation bodies may have been relatively large, in which case meteorites may provide a more unbiased record of early Solar System processes

Linking volatiles and microstructures in apatite from eucrites

Volatile elements play a key role in the dynamics of planetary evolution. As such there has been significant interest in their abundance and isotopic composition, particularly in the trace mineral apatite which is known to contain appreciable amounts of volatile elements [e.g. 1-4]. Whilst these works account for the textural context of the apatite grain and the surrounding minerals, the internal microstructure of the apatite has not been considered. Electron Backscatter Diffraction (EBSD) in extraterrestrial samples has mostly beenused to interpret the microstructures of zircon/baddeleyite for age dating and larger-scale plastic deformation features of samples [e.g 5-7]. Recently, however, the microtextures of meteoritic and lunar apatite and merrillite have been investigated [8-10]. As apatite is one of the major hosts of volatiles in planetary materials, any variation in structure observed may affect its volatile composition. In this study we therefore investiage the microstructure of apatite grains in eucrites with previously reported H [11] and preliminary Cl [12] isotopic data in order to investigate the relationship between crys-tallographic features and their volatile contents and isotopic compositions

Apatite Microstructures and its Volatile Composition in Eucrites

Apatiteis a common phosphate mineral in planetary materials known to contain appreciable amounts of volatiles (F, Cl, OH) [e.g. 1-4]. As such, apatite has recently been of significant interest in assessing the volatile evolution of various bodies within the Solar System via in-situ analysis (e.g. [5-7]). Whilst these works account for the textural context of the apatite grain and the surrounding mineralogy, less attention has been given to understanding as to how the structure of grains may be influenced by metamorphism and shock deformation. Electron Backscatter Diffraction (EBSD) analyses provide structural information at the μmand sub-μmlength scales. In extraterrestrial samples, it is largely used to interpret larger-scale plastic deformation [8] and shock deformation in geochronometers such as zircon and baddeleyite [e.g. 9-11]. Importantly, these studies highlight the importance of understanding deformation at the μm-scale when interpreting complex U-Pbdata and the mobility of Pb, a moderately volatile element. As yet, there have been no studies of how deformation-induced microstructures may influence the abundance and isotopic composition of volatiles in apatite in eucrites. In this study we investigate the microstructure of apatite grains in eucritesfor which H and Cl isotopic composition have been previously reported [12, 13], in order to explore the relationship between crystallographic features of apatite and its volatile content and isotopic composition in eucritesof different shock grades

The SCARE 2023 guideline: updating consensus Surgical CAse REport (SCARE) guidelines

BACKGROUND: The Surgical CAse REport (SCARE) guidelines were first published in 2016 as a tool for surgeons to document and report their surgical cases in a standardised and comprehensive manner. However, with advances in technology and changes in the healthcare landscape, it is important to revise and update these guidelines to ensure they remain relevant and valuable for surgeons. MATERIALS AND METHODS: The updated guidelines were produced through a Delphi consensus exercise. Members of the SCARE 2020 guidelines Delphi group, editorial board members, and peer reviewers were invited to participate. Potential contributors were contacted by e-mail. An online survey was completed to indicate their agreement with the proposed changes to the guideline items. RESULTS: A total of 54 participants were invited to participate and 44 (81.5%) completed the survey. There was a high degree of agreement among reviewers, with 36 items (83.7%) meeting the threshold for inclusion. CONCLUSION: Through a completed Delphi consensus exercise we present the SCARE 2023 guidelines. This will provide surgeons with a comprehensive and up-to-date tool for documenting and reporting their surgical cases while highlighting the importance of patient-centred care

More than just a side effect: Dynamic knee valgus and deadbug bridging performance in youth soccer players and alpine skiers have similar absolute values and asymmetry magnitudes but differ in terms of the direction of laterality

From a preventative perspective, leg axis and core stabilization capacities are important for soccer players and alpine skiers; however, due to different sport-specific demands, the role of laterality clearly differs and may result in functional long-term adaptations. The aims of this study are 1) to determine whether there are differences in leg axis and core stability between youth soccer players and alpine skiers and 2) between dominant and non-dominant sides, and 3) to explore the outcomes of applying common sport-specific asymmetry thresholds to these two distinct cohorts. Twenty-one highly trained/national-level soccer players (16.1 years, 95% CI: 15.6, 16.5) and 61 alpine skiers (15.7 years, 95% CI: 15.6, 15.8) participated in this study. Using a marker-based 3D motion capture system, dynamic knee valgus was quantified as the medial knee displacement (MKD) during drop jump landings, and core stability was quantified as the vertical displacement during deadbug bridging exercise (DBB $_{displacement}$ ). For the analysis of sports and side differences, a repeated-measures multivariate analysis of variance was used. For the interpretation of laterality, coefficients of variation (CV) and common asymmetry thresholds were applied. There were no differences in MKD or DBB $_{displacement}$ between soccer players and skiers or between the dominant and non-dominant sides, but there was an interaction effect side*sports for both variables (MKD: p = 0.040, η$^{2}$ p = 0.052; DBB $_{displacement}$ : p = 0.025, η$^{2}$ p = 0.061). On average, MKD was larger on the non-dominant side and DBB $_{displacement}$ laterality on the dominant side in soccer players, whereas this pattern was reversed in alpine skiers. Despite similar absolute values and asymmetry magnitudes of dynamic knee valgus and deadbug bridging performance in youth soccer players and alpine skiers, the effect on the direction of laterality was opposite even though much less pronounced. This may imply that sport-specific demands and potential laterality advantages should be considered when dealing with asymmetries in athletes