Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining the dominant chemical processes at work and, if in equilibrium, revealing planet formation histories. Transmission spectroscopy (for example, refs. (1,2)) provides the necessary means by constraining the abundances of oxygen- and carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution and high precision, which, together, are not achievable with previous observatories. Now that JWST has commenced science operations, we are able to observe exoplanets at previously uncharted wavelengths and spectral resolutions. Here we report time-series observations of the transiting exoplanet WASP-39b using JWST's Near InfraRed Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength photometric light curves span 2.0-4.0 micrometres, exhibit minimal systematics and reveal well defined molecular absorption features in the planet's spectrum. Specifically, we detect gaseous water in the atmosphere and place an upper limit on the abundance of methane. The otherwise prominent carbon dioxide feature at 2.8 micrometres is largely masked by water. The best-fit chemical equilibrium models favour an atmospheric metallicity of 1-100-times solar (that is, an enrichment of elements heavier than helium relative to the Sun) and a substellar C/O ratio. The inferred high metallicity and low C/O ratio may indicate significant accretion of solid materials during planet formation (for example, refs. (3,4)(,)) or disequilibrium processes in the upper atmosphere (for example, refs. (5,6)).

The Saturn-mass exoplanet WASP-39b has been the subject of extensive efforts to determine its atmospheric properties using transmission spectroscopy(1-4). However, these efforts have been hampered by modelling degeneracies between composition and cloud properties that are caused by limited data quality(5-9). Here we present the transmission spectrum of WASP-39b obtained using the Single-Object Slitless Spectroscopy (SOSS) mode of the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument on the JWST. This spectrum spans 0.6-2.8 mu m in wavelength and shows several water-absorption bands, the potassium resonance doublet and signatures of clouds. The precision and broad wavelength coverage of NIRISS/SOSS allows us to break model degeneracies between cloud properties and the atmospheric composition of WASP-39b, favouring a heavy-element enhancement ('metallicity') of about 10-30 times the solar value, a sub-solar carbon-to-oxygen (C/O) ratio and a solar-to-super-solar potassium-to-oxygen (K/O) ratio. The observations are also best explained by wavelength-dependent, non-grey clouds with inhomogeneous coverageof the planet's terminator.

Transmission spectroscopy(1-3) of exoplanets has revealed signatures of water vapour, aerosols and alkali metals in a few dozen exoplanet atmospheres(4,5). However, these previous inferences with the Hubble and Spitzer Space Telescopes were hindered by the observations' relatively narrow wavelength range and spectral resolving power, which precluded the unambiguous identification of other chemical species-in particular the primary carbon-bearing molecules(6,7). Here we report a broad-wavelength 0.5-5.5 mu m atmospheric transmission spectrum of WASP-39b(8), a 1,200 K, roughly Saturn-mass, Jupiter-radius exoplanet, measured with the JWST NIRSpec's PRISM mode(9) as part of the JWST Transiting Exoplanet Community Early Release Science Team Program(10-12). We robustly detect several chemical species at high significance, including Na (19 sigma), H2O (33 sigma), CO2 (28 sigma) and CO (7 sigma). The non-detection of CH4, combined with a strong CO2 feature, favours atmospheric models with a super-solar atmospheric metallicity. An unanticipated absorption feature at 4 mu m is best explained by SO2 (2.7 sigma), which could be a tracer of atmospheric photochemistry. These observations demonstrate JWST's sensitivity to a rich diversity of exoplanet compositions and chemical processes.

Modulation of photoassimilate export from the chloroplast is essential for controlling the distribution of fixed carbon in the cell and maintaining optimum photosynthetic rates. In this study, we identified chloroplast TRIOSE PHOSPHATE/PHOSPHATE TRANSLOCATOR 2 (CreTPT2) and CreTPT3 in the green alga Chlamydomonas (Chlamydomonas reinhardtii), which exhibit similar substrate specificities but whose encoding genes are differentially expressed over the diurnal cycle. We focused mostly on CreTPT3 because of its high level of expression and the severe phenotype exhibited by tpt3 relative to tpt2 mutants. Null mutants for CreTPT3 had a pleiotropic phenotype that affected growth, photosynthetic activities, metabolite profiles, carbon partitioning, and organelle-specific accumulation of H2O2. These analyses demonstrated that CreTPT3 is a dominant conduit on the chloroplast envelope for the transport of photoassimilates. In addition, CreTPT3 can serve as a safety valve that moves excess reductant out of the chloroplast and appears to be essential for preventing cells from experiencing oxidative stress and accumulating reactive oxygen species, even under low/moderate light intensities. Finally, our studies indicate subfunctionalization of the TRIOSE PHOSPHATE/PHOSPHATE TRANSLOCATOR (CreTPT) transporters and suggest that there are differences in managing the export of photoassimilates from the chloroplasts of Chlamydomonas and vascular plants.

The connection between the escape fraction of ionizing radiation (f(esc) ) and the properties of galaxies, such as stellar mass (M*), age, star-formation rate (SFR), and dust content, are key inputs for reionization models, but many of these relationships remain untested at high redshift. We present an analysis of a sample of 96 z similar to 3 galaxies from the Keck Lyman Continuum Spectroscopic Survey (KLCS). These galaxies have both sensitive Keck/LRIS spectroscopic measurements of the Lyman continuum (LyC) region, and multiband photometry that places constraints on stellar population parameters. We construct composite spectra from subsamples binned as a function of galaxy property and quantify the ionizing-photon escape for each composite. We find a significant anti-correlation between f(esc) and M-*, consistent with predictions from cosmological zoom-in simulations. We also find significant anti-correlation between f(esc) and E(B-V), encoding the underlying physics of LyC escape in our sample. We also find no significant correlation between f(esc) and either stellar age or specific SFR (= SFR/M-*), challenging interpretations that synchronize recent star formation and favorable conditions for ionizing escape. The galaxy properties now shown to correlate with f(esc) in the KLCS are Ly alpha equivalent width, UV Luminosity, M-*, SFR, and E(B-V), but not age or sSFR. This comprehensive analysis of galaxy properties and LyC escape at high redshift will be used to guide future models and observations of the reionization epoch.

Oxygen isotopic compositions of silicates in eclogites and whiteschists from the Kokchetav massif were analyzed by whole-grain CO2-laser fluorination methods. Systematic analyses yield extremely low delta(18)O for eclogites, as low as -3.9parts per thousand for garnet; these values are comparable with those reported for the Dabie-Sulu UHP eclogites. Oxygen isotopic compositions are heterogeneous in samples of eclogite, even on an outcrop scale. Schists have rather uniform oxygen isotope values compared to eclogites, and low delta(18)O is not observed. Isotope thermometry indicates that both eclogites and schists achieved high-temperature isotopic equilibration at 500-800 degreesC. This implies that retrograde metamorphic recrystallization barely modified the peak-metamorphic oxygen isotopic signatures. A possible geological environment to account for the low-delta(18)O basaltic protolith is a continental rift, most likely subjected to the conditions of a cold climate. After the basalt interacted with low delta(18)O meteoric water, it was tectonically inserted into the surrounding sedimentary units prior to, or during subduction and UHP metamorphism.

Multiple sulfur isotope system is a powerful new tracer for atmospheric, volcanic, and biological influences on sulfur cycles in the anoxic early Earth. Here, we report high-precision quadruple sulfur isotope analyses (S-32/S-33/S-34/S-36) of barite, pyrite in barite, and sulfides in related hydrothermal and igneous rocks Occurring in the ca. 3.5 Ga Dresser Formation, Western Australia. Our results indicate that observed isotopic variations are mainly controlled by mixing of mass-dependently (MD) and non-mass-dependently fractionated (non-MD) Sulfur reservoirs. Based on the quadruple Sulfur isotope systematics (delta S-34-Delta S-33-Delta S-36) for these minerals, four end-member Sulfur reservoirs have been recognized: (1) non-MD sulfate (delta S-34 = -5 +/- 2%; Delta S-33 = -3 +/- 1%); (2) MD sulfate (delta S-34 = +10 +/- 3%; (3) non-MD sulfur (delta S-34 > +6%; Delta S-33 > +4%); and (4) igneous MD sulfur (delta S-34 = Delta S-33 = 0%. The first and third components show it clear non-MD signatures, thus probably represent Sulfate and sulfur aerosol inputs. The MD sulfate component (2) is enriched in S-34(+10 +/- 3%) and may have originated from microbial and/ or abiotic disproportionation of volcanic S or SO2. Our results reconfirm that the Dresser barites contain small amounts of pyrite depleted in S-34 by 15-22% relative to the host barite. These barite-pyrite pairs exhibit a mass-dependent relationship of delta S-33/delta S-34 with slope less than 0.512, which is consistent with that expected for microbial Sulfate reduction and is significantly different from that of equilibrium fractionation (0.515). The barite-pyrite pairs also show up to 1% difference in Delta S-36 values and steep Delta S-36/Delta S-33 slopes, which deviate from the main Archean array (Delta S-36/Delta S-33 = -0.9) and are comparable to isotope effects exhibited by sulfate reducing microbes (Delta S-36/Delta S-33 = -5 to -11). These new lines of evidence support the existence of sulfate reducers at ca. 3.5 Ga, whereas microbial sulfur disproportionation may have been more limited than recently suggested. (C) 2008 Elsevier Ltd. All rights reserved.