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The C-H-O-N-S elements that constitute the outgassed atmosphere and exosphere have likely been delivered by chondritic materials to the Earth during planetary accretion and subsequently processed over billions of years of planetary differentiation. Although these elements are generally considered to be volatile, a large part of the accreted C-H-O-N-S on Earth must have been sequestered in the core and mantle, with the remaining part concentrated at the Earth’s surface (exosphere: atmosphere + ocean + crust ). The likely reason for this is that, depending on the prevailing pressure (P), temperature (T) and oxidation state (oxygen fugacity, fO 2 ) in the planet’s interior, the C-H-O-N-S elements can behave as siderophile, lithophile, refractory, magmatophile, or atmophile. It is not clear if these elements might be sequestered in the interiors of planets elsewhere, since the governing parameters of P-T-fO 2 during the diverse magmatic processes controlling magmatic differentiation vary greatly over time and from planet to planet. The magma ocean outgassed the first atmosphere, which was probably also the largest in terms of mass, but its nature and composition remain poorly known. Meanwhile, a significant, but unknown, part of the accreted C-H-O-N-S elements was sequestered in the core. These will probably never be liberated into the atmosphere. A secondary atmosphere was then fuelled by volcanism, driven by mantle convection and most likely enhanced by plate tectonics. The Earth still has active volcanism, and the volume and volatile contents of its magma are closely linked to geodynamics. Earth’s volcanoes have long emitted relatively oxidized gases, in contrast to Mars and Mercury. Mantle oxidation state seems to increase with planetary size, although the role of plate tectonics in changing the Earth’s mantle oxidation state remains poorly understood. Water contents of magma from elsewhere in the solar system are not so different from those produced by the Earth’s depleted mantle. Other elements (e.g. N, S, C) are unevenly distributed. A great diversity of speciation and quantity of magmatic gas emitted is found in planetary systems, with the key inputs being: 1 – degassing of the magma ocean, 2 – mantle oxidation state (and its evolution), and 3 – plate tectonics (vs. other styles of mantle convection). Many other parameters can affect these three inputs, of which planetary size is probably one of the most important.

Provenance records from sediments deposited offshore of the West Antarctic Ice Sheet (WAIS) can help identify past major ice retreat, thus constraining ice‐sheet models projecting future sea‐level rise. Interpretations from such records are, however, hampered by the ice obscuring Antarctica's geology. Here, we explore central West Antarctica's subglacial geology using basal debris from within the Byrd ice core, drilled to the bed in 1968. Sand grain microtextures and a high kaolinite content (∼38–42%) reveal the debris consists predominantly of eroded sedimentary detritus, likely deposited initially in a warm, pre‐Oligocene, subaerial environment. Detrital hornblende 40Ar/39Ar ages suggest proximal late Cenozoic subglacial volcanism. The debris has a distinct provenance signature, with: common Permian‐Early Jurassic mineral grains; absent early Ross Orogeny grains; a high kaolinite content; and high 143Nd/144Nd and low 87Sr/86Sr ratios. Detecting this “fingerprint” in Antarctic sedimentary records could imply major WAIS retreat, revealing the WAIS's sensitivity to future warming. Plain Language Summary Ice loss from the West Antarctic Ice Sheet (WAIS) could potentially raise global sea level by up to 4 m over the coming decades to centuries. However, projections of sea‐level contributions from the WAIS are highly uncertain. Understanding when the WAIS was smaller in warm times in the Earth's more recent history would reduce these uncertainties, but direct evidence for the most recent large‐scale WAIS retreat is lacking. Tracing the source of sediments deposited offshore will help detect WAIS retreat because, under a smaller WAIS, there would be more erosion of presently ice‐covered areas in central West Antarctica. However, the subglacial geology of central West Antarctica is poorly known, making it difficult to identify a WAIS retreat signal in sedimentary records. Here, we present new results from debris in the Byrd ice core, drilled in the center of the WAIS to its base in 1968. The mineralogical, geochemical and age compositions of the debris provide a distinct geological “fingerprint” that should be identifiable in sedimentary records. This fingerprint can be searched for in existing and upcoming Antarctic drill core records, which will ultimately help constrain the environmental conditions that would lead to future WAIS retreat and the resulting sea‐level rise. Key Points Debris from the base of the Byrd ice core comprises predominantly of sedimentary strata weathered before the onset of Antarctic glaciation 40Ar/39Ar dated hornblende grains support evidence for recent subglacial volcanism Byrd geochemical data reveal the provenance signature expected in marine sediments following major West Antarctic Ice Sheet retreat

Primitive interplanetary dust is expected to contain the earliest solar system components, including minerals and organic matter. We have recovered, from central Antarctic snow, ultracarbonaceous micrometeorites whose organic matter contains extreme deuterium (D) excesses (10 to 30 times terrestrial values), extending over hundreds of square micrometers. We identified crystalline minerals embedded in the micrometeorite organic matter, which suggests that this organic matter reservoir could have formed within the solar system itself rather than having direct interstellar heritage. The high D/H ratios, the high organic matter content, and the associated minerals favor an origin from the cold regions of the protoplanetary disk. The masses of the particles range from a few tenths of a microgram to a few micrograms, exceeding by more than an order of magnitude those of the dust fragments from comet 81P/Wild 2 returned by the Stardust mission.

In 1966, drilling at Camp Century, Greenland, recovered 3.44 m of subglacial material from beneath 1350 m of ice. Although prior analysis of this material showed that the core includes glacial sediment, ice, and sediment deposited during an interglacial period, the subglacial material had never been thoroughly studied. To better characterize this material, we analyzed 26 of the 30 core samples remaining in the archive. We performed a multiscale analysis including X-ray diffraction (XRD), micro-computed tomography (μCT), and scanning electron microscopy (SEM) to delineate stratigraphic units and assign facies based on inferred depositional processes. At the macroscale, quantitative X-ray diffraction revealed that quartz and feldspar dominated the sediment and that there was minimal variation in relative mineral abundance between samples. Mesoscale evaluation of the frozen material, using μCT scans, showed clear variations in the stratigraphy of the core characterized by the presence of bedding, grading, and sorting. Microscale grain size and shape analysis, conducted using scanning electron microscopy, showed an abundance of fine-grained materials in the lower part of the core and no correspondence between grain shape parameters and sedimentary structures. These multiscale data define five distinct stratigraphic units within the core based on sedimentary process; k-means clustering analysis supports this unit delineation. Our observations suggest that ice retreat uncovered the Camp Century region, exposing weathered basal till (Unit 1), now covered by a remnant of basal ice or firn (Unit 2). Continued ice-free conditions led to till disruption by liquid water causing a mass movement (Unit 3) and deposition of water-worked sediment (units 4–5). Analysis of the Camp Century subglacial material reveals a diverse stratigraphy preserved below the ice that recorded episodes of glaciated and deglaciated conditions in northwestern Greenland. Our physical, geochemical, and mineralogic analyses illuminate the history of deposition, weathering, and sediment transport preserved under the ice and show the promise of subglacial materials to increase our knowledge of past ice sheet behavior over time.

Metasomatism refers to the process during which a pre-existing rock undergoes compositional and mineralogical transformations associated with chemical reactions triggered by the reaction of fluids which invade the protolith. It changes chemical compositions of minerals, promotes their dissolution and precipitation of new minerals. In this paper, we review metasomatic alteration of type 3 ordinary (H, L, LL) and carbonaceous (CV, CO, CK) chondrites, including ( i ) secondary mineralization, ( ii ) physicochemical conditions, ( iii ) chronology ( 53 Mn- 53 Cr, 26 Al- 26 Mg, 129 I- 129 Xe) of metasomatic alteration, ( iv ) records of metasomatic alteration in H, O, N, C, S, and Cl isotopic systematics, ( v ) effects of metasomatic alteration on O- and Al-Mg-isotope systematics of primary minerals in chondrules and refractory inclusions, and ( vi ) sources of water ices in metasomatically altered CV, CO, and ordinary chondrites, and outline future studies.