We present Keck Planet Imager and Characterizer (KPIC) high-resolution (R similar to 35,000) K-band thermal emission spectroscopy of the ultrahot Jupiter WASP-33b. The use of KPIC's single-mode fibers greatly improves both blaze and line-spread stabilities relative to slit spectrographs, enhancing the cross-correlation detection strength. We retrieve the dayside emission spectrum with a nested-sampling pipeline, which fits for orbital parameters, the atmospheric pressure-temperature profile, and the molecular abundances. We strongly detect the thermally inverted dayside and measure mass-mixing ratios for CO (logCO(MMR) = -1.1(-0.6)(+0.4)), H2O (logH(2)O(MMR) = -4.1(-0.9)(+0.7)), and OH (logOH(MMR) = -2.1(-1.1)(+0.5)), suggesting near-complete dayside photodissociation of H2O. The retrieved abundances suggest a carbon- and possibly metal-enriched atmosphere, with a gas-phase C/O ratio of 0.8(-0.2)(+0.1), consistent with the accretion of high-metallicity gas near the CO2 snow line and post-disk migration or with accretion between the soot and H2O snow lines. We also find tentative evidence for (CO)-C-12/(CO)-C-13 similar to 50, consistent with values expected in protoplanetary disks, as well as tentative evidence for a metal-enriched atmosphere (2-15 x solar). These observations demonstrate KPIC's ability to characterize close-in planets and the utility of KPIC's improved instrumental stability for cross-correlation techniques.

We present high-resolution K-band emission spectra of the quintessential hot Jupiter HD 189733 b from the Keck Planet Imager and Characterizer. Using a Bayesian retrieval framework, we fit the dayside pressure-temperature profile, orbital kinematics, mass-mixing ratios of H2O, CO, CH4, NH3, HCN, and H2S, and the (CO)-C-13/(CO)-C-12 ratio. We measure mass fractions of logH(2)O = -2.0(-0.4)(+0.4) and logCO = -2.2(-0.5)(+0.5), and place upper limits on the remaining species. Notably, we find logCH(4) < -4.5 at 99% confidence, despite its anticipated presence at the equilibrium temperature of HD 189733 b assuming local thermal equilibrium. We make a tentative (similar to 3 sigma) detection of (CO)-C-13, and the retrieved posteriors suggest a C-12/C-13 ratio similar to or substantially less than the local interstellar value. The possible C-13 enrichment would be consistent with accretion of fractionated material in ices or in the protoplanetary disk midplane. The retrieved abundances correspond to a substantially substellar atmospheric C/O = 0.3 +/- 0.1, while the carbon and oxygen abundances are stellar to slightly superstellar, consistent with core-accretion models which predict an inverse correlation between C/O and metallicity. The specific combination of low C/O and high metallicity suggests significant accretion of solid material may have occurred late in the formation process of HD 189733 b.

Tension remains between the observed and modeled properties of substellar objects, but objects in binary orbits, with known dynamical masses, can provide a way forward. HD 72946 B is a recently imaged brown dwarf companion to a nearby, solar-type star. We achieve similar to 100 mu as relative astrometry of HD 72946 B in the K band using VLTI/GRAVITY, unprecedented for a benchmark brown dwarf. We fit an ensemble of measurements of the orbit using orbitize! and derive a strong dynamical mass constraint M B = 69.5 +/- 0.5 M Jup assuming a strong prior on the host star mass M A = 0.97 +/- 0.01 M circle dot from an updated stellar analysis. We fit the spectrum of the companion to a grid of self-consistent BT-Settl-CIFIST model atmospheres, and perform atmospheric retrievals using petitRADTRANS. A dynamical mass prior only marginally influences the sampled distribution of effective temperature, but has a large influence on the surface gravity and radius, as expected. The dynamical mass alone does not strongly influence retrieved pressure-temperature or cloud parameters within our current retrieval setup. Independently of the cloud prescription and prior assumptions, we find agreement within +/- 2 sigma between the C/O of the host (0.52 +/- 0.05) and brown dwarf (0.43-0.63), as expected from a molecular cloud collapse formation scenario, but our retrieved metallicities are implausibly high (0.6-0.8) in light of the excellent agreement of the data with the solar-abundance model grid. Future work on our retrieval framework will seek to resolve this tension. Additional study of low surface gravity objects is necessary to assess the influence of a dynamical mass prior on atmospheric analysis.

We present the first volatile contents (H2O, CO2, Cl, F, S) of young (< 6 Ma) submarine basaltic glasses from the Phoenix and West Scotia mid-ocean ridges and the Bransfield Strait back-arc of the South Shetland subduction zone in the Antarctic Peninsula. The volatile contents of the MORB glasses correspond well with those of published Pacific MORB and reflect covariations in source enrichment and extent of melting. Our results support the hypothesis that decreasing spreading rates at the Phoenix Ridge resulted in preferential melting of less abundant enriched MORB mantle, due to its greater fertility and higher volatile contents, relative to the more abundant depleted MORB mantle. The volatile contents of the Bransfield Strait back-arc glasses correlate with geochemical indicators of subduction processes and reveal an along-axis spatial distribution consistent with a toroidal inflow of sub-slab asthenosphere around the edges of the subducting plate into the mantle wedge. This inflow should be considered when assessing spatial and geochemical variability at subduction zones, particularly those with slab windows and tears. A small group of Bransfield Strait samples have volatile contents that do not correlate with geochemical signals of subduction influence. We speculate that these samples reflect flux melting of residual enriched mantle brought beneath the Bransfield Strait via corner flow following recent alkaline magmatism in the far eastern regions of the Antarctic Peninsula. Our new data on lavas from the W7 segment of the West Scotia Ridge reveal their source was significantly affected by subduction processes. Unexpectedly, these lavas have CO2-H2O pressures of vapor saturation that suggest they were collected in-situ and erupted relatively recently (-6 Ma), at odds with previous interpretations of their origins. We suggest they originated from a subduction-modified mantle (lithosphere or asthenosphere) left behind by the eastward-migrating South Sandwich subduction zone sometime over the past -30 Myr. These lavas demonstrate the long-lasting effects of subduction processes on the upper mantle and their potential to influence melt compositions even in non-subduction environments today. We use the compositions of lavas from the Phoenix Ridge and Bransfield Strait to estimate mantle potential temperatures; our results agree well with global estimates for mid-ocean ridges and subduction zones, respectively.

The thermal structure of subduction zones is fundamental to our understanding of physical and chemical processes that occur at active convergent plate margins. These include magma generation and related arc volcanism, shallow and deep seismicity, and metamorphic reactions that can release fluids. Computational models can predict the thermal structure to great numerical precision when models are fully described but this does not guarantee accuracy or applicability. In a trio of companion papers, the construction of thermal subduction zone models, their use in subduction zone studies, and their link to geophysical and geochemical observations are explored. In part I, the motivation to understand the thermal structure is presented based on experimental and observational studies. This is followed by a description of a selection of thermal models for the Japanese subduction zones.

The thermal structure of subduction zones is fundamental to our understanding of the physical and chemical processes that occur at active convergent plate margins. These include magma generation and related arc volcanism, shallow and deep seismicity, and metamorphic reactions that can release fluids. Computational models can predict the thermal structure to great numerical precision when models are fully described but this does not guarantee accuracy or applicability. In a trio of companion papers, the construction of thermal subduction zone models, their use in subduction zone studies, and their link to geophysical and geochemical observations are explored. In this part II, the finite element techniques that can be used to predict thermal structure are discussed in an introductory fashion along with their verification and validation.Steady-state thermal structure for the updated subduction zone benchmark. a) Temperature predicted by TF for case 1; b) temperature difference between TF and Sepran using the penalty function (PF) method for case 1 at fm=1 where fm represents the smallest element sizes in the finite element grids near the coupling point; c) slab top temperature comparison for case 1; and d)-f) as a)-c) but now for case 2. The star indicates the position or temperature conditions at the coupling point.

The thermal structure of subduction zones is fundamental to our understanding of the physical and chemical processes that occur at active convergent plate margins. These include magma generation and related arc volcanism, shallow and deep seismicity, and metamorphic reactions that can release fluids. Computational models can predict the thermal structure to great numerical precision when models are fully described but this does not guarantee accuracy or applicability. In a trio of companion papers, the construction of thermal subduction zone models, their use in subduction zone studies, and their link to geophysical and geochemical observations are explored. In this last part, we discuss how independent finite element approaches predict the thermal structure of the global subduction system and investigate how well these predictions correspond to geophysical, geochemical, and petrological observations.