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We review a large body of available meteoritic and stellar halogen data in the literature used for solar system abundances (i.e., representative abundances of the solar system at the time of its formation) and associated analytical problems. Claims of lower solar system chlorine, bromine and iodine abundances from recent analyses of CI-chondrites are untenable because of incompatibility of such low values with nuclear abundance systematics and independent measurements of halogens in the Sun and other stars. We suspect analytical problems associated with these peculiar rock types have led to lower analytical results in several studies. We review available analytical procedures and concentrations of halogens in chondrites. Our recommended values are close to pre-viously accepted values. Average concentrations by mass for CI-chondrites are F = 92 ± 20 ppm, Cl = 717 ± 110 ppm, Br = 3.77 ± 0.90 ppm, and I = 0.77 ± 0.31 ppm. The meteoritic abundances on the atomic scale normalized to N(Si) =106 are N(F) = 1270 ± 270, N(Cl) = 5290 ± 810, N(Br) = 12.3 ± 2.9, and N(I) = 1.59 ± 0.64. The meteoritic logarithmic abundances scaled to present-day photospheric abundances with log N(H) = 12 are A(F) = 4.61 ± 0.09, A(Cl) = 5.23 ± 0.06, A(Br) = 2.60 ± 0.09, and A(I) = 1.71 ± 0.15. These are our recommended present-day solar system abundances. These are compared to the present-day solar values derived from sunspots of N(F) = 776 ± 260, A(F) = 4.40 ± 0.25, and N(Cl) = 5500 ± 810, A(Cl) = 5.25 ± 0.12. The recommended solar system abundances based on meteorites are consistent with F and Cl abundance ratios measured independently in other stars and other astronomical environments. The recently determined chlorine abundance of 776 ± 21 ppm by Yokoyama et al. (2022) for the CI-chondrite-like asteroid Ryugu is consistent with the chlorine abundance evaluated for CI-chondrites here. Historically, the halogen abundances have been quite uncertain and unfortunately remain so. We still need reliable measurements from large, representative, and well-homogenized CI-chondrite samples. The analysis of F, Br, and I in Ryugu samples should also help to obtain more reliable halogen abundances. Updated equilibrium 50 % condensation temperatures from our previous work (Lodders, 2003; Fegley and Schaefer, 2010; Fegley and Lodders, 2018) are 713 K (F), 427 K (Cl), 392 K (Br) and 312 K (I) at a total pressure of 10^ 4 bar for a solar composition gas. We give condensation temperatures considering solid-solution as well as kinetic inhibition effects. Condensation temperatures computed with lower halogen abundances do not represent the correct condensation temperatures from a solar composition gas. 

olar elemental abundances, or solar system elemental abundances refer to the complement of chemical elements in the entire solar system. The sun contains more than 99-percent of the mass in the solar system and therefore the composition of the sun is a good proxy for the composition of the overall solar system. The solar system composition can be taken as the overall composition of the molecular cloud within the interstellar medium from which the solar system formed 4.567 billion years ago. Active research areas in astronomy and cosmochemistry model collapse of a molecular cloud of solar composition into a star with a planetary system, and the physical and chemical fractionation of the elements during planetary formation and differentiation. The solar system composition is the initial composition from which all solar system objects (the sun, terrestrial planets, gas giant planets, planetary satellites and moons, asteroids, Kuiper-belt objects, and comets) were derived. Other dwarf stars (with hydrostatic Hydrogen-burning in their cores) like our Sun (type G2V dwarf star) within the solar neighborhood have compositions similar to our Sun and the solar system composition. In general, differential comparisons of stellar compositions provide insights about stellar evolution as functions of stellar mass and age, and ongoing nucleosynthesis; but also about galactic chemical evolution when elemental compositions of stellar populations across our Milky Way Galaxy is considered. Comparisons to solar composition can reveal element destruction (e.g., Li) in the sun and in other dwarf stars. The comparisons also show element production of e.g., C, N, O, and the heavy elements made by the s-process in low- to intermediate mass stars (3-7 solar masses) after these evolved from their dwarf-star stage into red giant stars (where hydrogen and helium burning can occur in shells around their cores). The solar system abundances are and have been a critical test composition for nucleosynthesis models and models of Galactic chemical evolution, which aim ultimately to track the production of the elements heavier than hydrogen and helium in the generation of stars that came forth after the Big Bang 13.4 billion years ago. Article at: https://oxfordre.com/planetaryscience/view/10.1093/acrefore/9780190647926.001.0001/acrefore-9780190647926-e-145 

Lithium’s story spans the history of the universe and is one that links to all its largest-scale processes: big bang nucleosyntheses, the evolution of stars, and galactic chemical evolution. Lithium was the only metal produced in the big bang, alongside the gases H and He. Stars destroy both stable isotopes of Li easily, yet we still have Li today, even after generations of stars have come and gone. Ongoing production of Li by galactic cosmic rays and by a limited number of Li-producing nuclear reactions and transport processes in some rare types of stars keeps lithium present in the universe. 

Condensation of the ultrarefractory REE as oxides before Ca-bearing condensates at lower total pressures and [Fe/H] removes the need for removal of hibonite or perovskite from equilibrium with gas within an extremely small T interval after they become stable. 

We describe a novel fractionation mechanism that can significantly alter the bulk composition of rocky planets by fractional vaporization and subsequent loss of a steam atmosphere into which rocky elements can dissolve. 

Presolar grains constitute the remnants of stars that existed before the formation of the solar system. In addition to providing direct information on the materials from which the solar system formed, these grains provide ground-truth information for models of stellar evolution and nucleosynthesis. Here we report the in situ identification of two unique presolar graphite grains from the primitive meteorite LaPaz Icefield 031117. Based on these two graphite grains, we estimate a bulk presolar graphite abundance of {5}-3+7 ppm in this meteorite. One of the grains (LAP-141) is characterized by an enrichment in 12C and depletions in 33,34S, and contains a small iron sulfide subgrain, representing the first unambiguous identification of presolar iron sulfide. The other grain (LAP-149) is extremely 13C-rich and 15N-poor, with one of the lowest 12C/13C ratios observed among presolar grains. Comparison of its isotopic compositions with new stellar nucleosynthesis and dust condensation models indicates an origin in the ejecta of a low-mass CO nova. Grain LAP-149 is the first putative nova grain that quantitatively best matches nova model predictions, providing the first strong evidence for graphite condensation in nova ejecta. Our discovery confirms that CO nova graphite and presolar iron sulfide contributed to the original building blocks of the solar system.