Nitrite, an intermediate product of the oxidation of ammonia to nitrate (nitrification), accumulates in upper oceans, forming the primary nitrite maximum (PNM). Nitrite concentrations in the PNM are relatively low in the western North Pacific subtropical gyre (wNPSG), where eddies are frequent and intense. To explain these low nitrite concentrations, we investigated nitrification in cyclonic eddies in the wNPSG. We detected relatively low half-saturation constants (i.e., high substrate affinities) for ammonia and nitrite oxidation at 150 to 200 meter water depth. Eddy-induced displacement of high-affinity nitrifiers and increased substrate supply enhanced ammonia and nitrite oxidation, depleting ambient substrate concentrations in the euphotic zone. Nitrite oxidation is more strongly enhanced by the cyclonic eddies than ammonia oxidation, reducing concentrations and accelerating the turnover of nitrite in the PNM. These findings demonstrate a spatial decoupling of the two steps of nitrification in response to mesoscale processes and provide insights into physical-ecological controls on the PNM.

We present preexplosion optical and infrared (IR) imaging at the site of the type II supernova (SN II) 2023ixf in Messier 101 at 6.9 Mpc. We astrometrically registered a ground-based image of SN 2023ixf to archival Hubble Space Telescope (HST), Spitzer Space Telescope (Spitzer), and ground-based near-IR images. A single point source is detected at a position consistent with the SN at wavelengths ranging from HST R band to Spitzer 4.5 mu m. Fitting with blackbody and red supergiant (RSG) spectral energy distributions (SEDs), we find that the source is anomalously cool with a significant mid-IR excess. We interpret this SED as reprocessed emission in a 8600 R-circle dot circumstellar shell of dusty material with a mass similar to 5 x 10(-5)M(circle dot) surrounding a log(L/L-circle dot) = 4.74 +/- 0.07 and T-eff 3920(-160)(+200) K RSG. This luminosity is consistent with RSG models of initial mass 11M(circle dot), depending on assumptions of rotation and overshooting. In addition, the counterpart was significantly variable in preexplosion Spitzer 3.6 and 4.5 mu m imaging, exhibiting similar to 70% variability in both bands correlated across 9 yr and 29 epochs of imaging. The variations appear to have a timescale of 2.8 yr, which is consistent with kappa-mechanism pulsations observed in RSGs, albeit with a much larger amplitude than RSGs such as alpha Orionis (Betelgeuse).

Carbon monoxide (CO) is predicted to be the dominant carbon-bearing molecule in giant planet atmospheres and, along with water, is important for discerning the oxygen and therefore carbon-to-oxygen ratio of these planets. The fundamental absorption mode of CO has a broad, double-branched structure composed of many individual absorption lines from 4.3 to 5.1 mu m, which can now be spectroscopically measured with JWST. Here we present a technique for detecting the rotational sub-band structure of CO at medium resolution with the NIRSpec G395H instrument. We use a single transit observation of the hot Jupiter WASP-39b from the JWST Transiting Exoplanet Community Early Release Science (JTEC ERS) program at the native resolution of the instrument (R similar to 2700) to resolve the CO absorption structure. We robustly detect absorption by CO, with an increase in transit depth of 264 +/- 68 ppm, in agreement with the predicted CO contribution from the best-fit model at low resolution. This detection confirms our theoretical expectations that CO is the dominant carbon-bearing molecule in WASP-39b's atmosphere and further supports the conclusions of low C/O and supersolar metallicities presented in the JTEC ERS papers for WASP-39b.

Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking the formation and evolution of exoplanetary systems(1,2). Access to the chemical inventory of an exoplanet requires high-precision observations, often inferred from individual molecular detections with low-resolution space-based(3-5) and high-resolution ground-based(6-8) facilities. Here we report the medium-resolution (R & AP; 600) transmission spectrum of an exoplanet atmosphere between 3 and 5 mu m covering several absorption features for the Saturn-mass exoplanet WASP-39b (ref. (9)), obtained with the Near Infrared Spectrograph (NIRSpec) G395H grating of JWST. Our observations achieve 1.46 times photon precision, providing an average transit depth uncertainty of 221 ppm per spectroscopic bin, and present minimal impacts from systematic effects. We detect significant absorption from CO2 (28.5 sigma) and H2O (21.5 sigma), and identify SO2 as the source of absorption at 4.1 mu m (4.8 sigma). Best-fit atmospheric models range between 3 and 10 times solar metallicity, with sub-solar to solar C/O ratios. These results, including the detection of SO2, underscore the importance of characterizing the chemistry in exoplanet atmospheres and showcase NIRSpec G395H as an excellent mode for time-series observations over this critical wavelength range(10).

Close-in giant exoplanets with temperatures greater than 2,000K ('ultra-hot Jupiters') have been the subject of extensive efforts to determine their atmospheric properties using thermal emission measurements from the Hubble Space Telescope (HST) and Spitzer Space Telescope1-3. However, previous studies have yielded inconsistent results because the small sizes of the spectral features and the limited information content of the data resulted in high sensitivity to the varying assumptions made in the treatment of instrument systematics and the atmosphericretrieval analysis3-12. Here we present a dayside thermal emission spectrum of the ultra-hot Jupiter WASP-18b obtained with the NIRISS13 instrument on the JWST. The data span 0.85 to 2.85mum in wavelength at an average resolving power of 400 and exhibit minimal systematics. The spectrum shows three wateremission features (at >6sigma confidence) and evidence for optical opacity, possiblyattributable to H-, TiO and VO (combined significance of 3.8sigma). Models that fit the data require a thermal inversion, molecular dissociation as predicted by chemical equilibrium, a solar heavy-element abundance ('metallicity', [Formula: see text] times solar) and a carbon-to-oxygen (C/O) ratio less than unity. The data also yield a dayside brightness temperature map, which shows a peak in temperature near the substellar point that decreases steeply and symmetrically with longitude towards the terminators.

One of the frontiers for advancing what is known about dark matter lies in using strong gravitational lenses to characterize the population of the smallest dark matter haloes. There is a large volume of information in strong gravitational lens images - the question we seek to answer is to what extent we can refine this information. To this end, we forecast the detectability of a mixed warm and cold dark matter scenario using the anomalous flux ratio method from strong gravitational lensed images. The halo mass function of the mixed dark matter scenario is suppressed relative to cold dark matter but still predicts numerous low-mass dark matter haloes relative to warm dark matter. Since the strong lensing signal receives a contribution from a range of dark matter halo masses and since the signal is sensitive to the specific configuration of dark matter haloes, not just the halo mass function, degeneracies between different forms of suppression in the halo mass function, relative to cold dark matter, can arise. We find that, with a set of lenses with different configurations of the main deflector and hence different sensitivities to different mass ranges of the halo mass function, the different forms of suppression of the halo mass function between the warm dark matter model and the mixed dark matter model can be distinguished with 40 lenses with Bayesian odds of 30:1.

Distinguishing deep lower mantle heterogeneities and resolving their physical and chemical properties are challenging due to the difficulty in achieving severe high-temperature and high-pressure conditions simultaneously in mineral experiments. Deep-seated mantle plumes bring these heterogeneities to the Earth's surface, therefore providing a unique insight into the Earth's deep interior. Here, we link the surface temperature fluctuation of mantle plume to the properties of deep-mantle heterogeneities via three-dimensional geodynamic modeling. Our results show that high-viscosity primordial mantle materials significantly increase the surface plume temperature due to their excessive viscous heating, whereas high-density oceanic crust slightly reduces it. Give some estimates for the maximum plume fluctuation temperature through time, the survival of scattered primordial blobs with a high viscosity contrast of -10-50 times in the deep-mantle reservoir is required. The temperature variations of the thermochemical mantle plume likely control the observed multiple volcanic episodes of large igneous provinces and periodic changes of volcanic flux along hotspot tracks.& COPY; 2023 Elsevier B.V. All rights reserved.

Photochemistry is a fundamental process of planetary atmospheres that regulates the atmospheric composition and stability(1). However, no unambiguous photochemical products have been detected in exoplanet atmospheres so far. Recent observations from the JWST Transiting Exoplanet Community Early Release Science Program(2,3) found a spectral absorption feature at 4.05 mu m arising from sulfur dioxide (SO2) in the atmosphere of WASP-39b. WASP-39b is a 1.27-Jupiter-radii, Saturn-mass (0.28 M-J) gas giant exoplanet orbiting a Sun-like star with an equilibrium temperature of around 1,100 K (ref. (4)). The most plausible way of generating SO2 in such an atmosphere is through photochemical processes(5,6). Here we show that the SO2 distribution computed by a suite of photochemical models robustly explains the 4.05-mu m spectral feature identified by JWST transmission observations(7) with NIRSpec PRISM (2.7s)(8) and G395H (4.5s)(9). SO2 is produced by successive oxidation of sulfur radicals freed when hydrogen sulfide (H2S) is destroyed. The sensitivity of the SO2 feature to the enrichment of the atmosphere by heavy elements (metallicity) suggests that it can be used as a tracer of atmospheric properties, with WASP-39b exhibiting an inferred metallicity of about 10x solar. We further point out that SO2 also shows observable features at ultraviolet and thermal infrared wavelengths not available from the existing observations.

Photoevaporation is a potential explanation for several features within exoplanet demographics. Atmospheric escape observed in young Neptune-sized exoplanets can provide insight into and characterize which mechanisms drive this evolution and at what times they dominate. AU Mic b is one such exoplanet, slightly larger than Neptune (4.19 R (& OPLUS;)). It closely orbits a 23 Myr pre-main-sequence M dwarf with an orbital period of 8.46 days. We obtained two visits of AU Mic b at Ly & alpha; with Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph. One flare within the first HST visit is characterized and removed from our search for a planetary transit. We present a nondetection in our first visit, followed by the detection of escaping neutral hydrogen ahead of the planet in our second visit. The outflow absorbed & SIM;30% of the star's Ly & alpha; blue wing 2.5 hr before the planet's white-light transit. We estimate that the highest-velocity escaping material has a column density of 10(13.96) cm(-2) and is moving 61.26 km s(-1) away from the host star. AU Mic b's large high-energy irradiation could photoionize its escaping neutral hydrogen in 44 minutes, rendering it temporarily unobservable. Our time-variable Ly & alpha; transit ahead of AU Mic b could also be explained by an intermediate stellar wind strength from AU Mic that shapes the escaping material into a leading tail. Future Ly & alpha; observations of this system will confirm and characterize the unique variable nature of its Ly & alpha; transit, which, combined with modeling, will tune the importance of stellar wind and photoionization.