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The exploration of our solar system is being radically changed since the beginning of operations of the James Webb Space Telescope (JWST) in mid 2022. JWST’s extraordinary sensitivity and instrumentation allow for sensitive searches for the building blocks of life and to test for habitability, also enabling new discoveries on small bodies to giant planets across our solar system and beyond.

Abstract In an attempt to understand the findings presented in the Comment by Greaves et al. (2023, https://doi.org/10.1029/2023GL103539), we followed their data analysis methodology, omitting the hot and cold‐load calibrations that are an important part of the standard SOFIA GREAT instrument calibration procedure. This process requires scaling of the Venus off‐source spectra by an arbitrary factor, which in turn introduces residuals of the intrinsic receiver bandpass shape as spurious components in the resulting line/continuum spectra. Although these additional artifacts can be reduced via Fourier‐domain spectral filtering, their removal depends on an ill‐constrained interpolation of the Venus continuum across the PH3 spectral line positions, resulting in an unreliable final spectrum. We therefore conclude that the PH3 lines claimed to be detected in the Comment by Greaves et al. (2023, https://doi.org/10.1029/2023GL103539) originate from data/analysis artifacts, and confirm our original result that there is no evidence for phosphine in the SOFIA Venus data.

The James Webb Space Telescope (JWST) North Ecliptic Pole (NEP) Time-domain Field (TDF) is a >14′ diameter field optimized for multiwavelength time-domain science with JWST. It has been observed across the electromagnetic spectrum both from the ground and from space, including with the Hubble Space Telescope (HST). As part of HST observations over three cycles (the “TREASUREHUNT” program), deep images were obtained with the Wide Field Camera on the Advanced Camera for Surveys in F435W and F606W that cover almost the entire JWST NEP TDF. Many of the individual pointings of these programs partially overlap, allowing an initial assessment of the potential of this field for time-domain science with HST and JWST. The cumulative area of overlapping pointings is ∼88 arcmin ^2 , with time intervals between individual epochs that range between 1 day and 4+ yr. To a depth of m _AB ≃ 29.5 mag (F606W), we present the discovery of 12 transients and 190 variable candidates. For the variable candidates, we demonstrate that Gaussian statistics are applicable and estimate that ∼80 are false positives. The majority of the transients will be supernovae, although at least two are likely quasars. Most variable candidates are active galactic nuclei (AGNs), where we find 0.42% of the general z ≲ 6 field galaxy population to vary at the ∼3 σ level. Based on a 5 yr time frame, this translates into a random supernova areal density of up to ∼0.07 transients arcmin ^−2 (∼245 deg ^−2 ) per epoch and a variable AGN areal density of ∼1.25 variables arcmin ^−2 (∼4500 deg ^−2 ) to these depths.

46P/Wirtanen is a Jupiter-family comet, probably originating from the solar system’s Kuiper Belt, that now resides on a 5.4 yr elliptical orbit. During its 2018 apparition, comet 46P passed unusually close to the Earth (within 0.08 au), presenting an outstanding opportunity for close-up observations of its inner coma. Here we present observations of HCN, H ^13 CN, and HC ^15 N emission from 46P using the Atacama Compact Array. The data were analyzed using the SUBLIME non-LTE radiative transfer code to derive ^12 C/ ^13 C and ^14 N/ ^15 N ratios. The HCN/H ^13 CN ratio is found to be consistent with a lack of significant ^13 C fractionation, whereas the HCN/HC ^15 N ratio of 68 ± 27 (using our most conservative 1 σ uncertainties), indicates a strong enhancement in ^15 N compared with the solar and terrestrial values. The observed ^14 N/ ^15 N ratio is also significantly lower than the values of ∼140 found in previous comets, implying a strong ^15 N enrichment in 46P’s HCN. This indicates that the nitrogen in Jupiter-family comets could reach larger isotopic enrichments than previously thought, with implications for the diversity of ^14 N/ ^15 N ratios imprinted into icy bodies at the birth of the solar system.

The ortho-to-para ratio (OPR) of formaldehyde (H _2 CO) has been used as a probe to estimate the formation temperature of molecules in interstellar, circumstellar, and cometary environments, relying on the assumption that nuclear spin conversion is extremely slow, preserving the OPR from molecular formation. An OPR for H _2 CO less than 3 corresponds to a spin temperature below 30 K and has been proposed to result from formation at low temperatures within an ice, whereas an OPR of 3 is interpreted as arising from warmer formation in the gas phase. In spite of this common assumption, there is no laboratory evidence in the literature to date in support of it. Here, in the first study of its kind for H _2 CO, we report rotational spectroscopy measurements of the OPR of H _2 CO sublimated after its formation in methanol (CH _3 OH) ice samples that were photolyzed by ultraviolet light at 10, 15, 20, and 40 K. None of the measured OPR values correlated with the ice formation temperature.

Gas-phase molecules in cometary atmospheres (comae) originate primarily from (1) outgassing by the nucleus, (2) sublimation of icy grains in the near-nucleus coma, and (3) coma (photo)chemical processes. However, the majority of cometary gases observed at radio wavelengths have yet to be mapped, so their production/release mechanisms remain uncertain. Here we present observations of six molecular species toward comet 46P/Wirtanen, obtained using the Atacama Large Millimeter/submillimeter Array during the comet’s unusually close (∼0.1 au) approach to Earth in 2018 December. Interferometric maps of HCN, CH _3 OH, CH _3 CN, H _2 CO, CS, and HNC were obtained at an unprecedented sky-projected spatial resolution of up to 25 km, enabling the nucleus and coma sources of these molecules to be accurately quantified. The HCN, CH _3 OH, and CH _3 CN spatial distributions are consistent with production by direct outgassing from (or very close to) the nucleus, with a significant proportion of the observed CH _3 OH originating from sublimation of icy grains in the near-nucleus coma (at a scale length L _p = 36 ± 7 km). On the other hand, H _2 CO, CS, and HNC originate primarily from distributed coma sources (with L _p values in the range 550–16,000 km), the identities of which remain to be established. The HCN, CH _3 OH, and HNC abundances in 46P are consistent with the average values previously observed in comets, whereas the H _2 CO, CH _3 CN, and CS abundances are relatively low.

Observations of the sungrazing comet C/2012 S1 (ISON) were carried out using the Atacama Large Millimeter/submillimeter Array at a heliocentric distance of 0.58–0.54 au (pre-perihelion) on 2013 November 16–17. Temporally resolved measurements of the coma distributions of HNC, CH3OH, H2CO, and dust were obtained over the course of about an hour on each day. During the period UT 10:10–11:00 on November 16, the comet displayed a remarkable drop in activity, manifested as a >42% decline in the molecular line and continuum fluxes. The H2CO observations are consistent with an abrupt, ≈50% reduction in the cometary gas production rate soon after the start of our observations. On November 17, the total observed fluxes remained relatively constant during a similar period, but strong variations in the morphology of the HNC distribution were detected as a function of time, indicative of a clumpy, intermittent outflow for this species. Our observations suggest that at least part of the detected HNC originated from degradation of nitrogen-rich organic refractory material, released intermittently from confined regions of the nucleus. By contrast, the distributions of CH3OH and H2CO during the November 17 observations were relatively uniform, consistent with isotropic outflow and stable activity levels for these species. These results highlight a large degree of variability in the production of gas and dust from comet ISON during its pre-perihelion outburst, consistent with repeated disruption of the nucleus interspersed with periods of relative quiescence. [ABSTRACT FROM AUTHOR]

We present spatially and spectrally resolved observations of CH3OH emission from comet C/2012 K1 (PanSTARRS), using the Atacama Large Millimeter/submillimeter Array on 2014 June 28–29. Two-dimensional maps of the line-of-sight average rotational temperature (Trot) were derived, covering spatial scales 0.″3–1.″8 (corresponding to sky-projected distances ρ ∼ 500–2500 km). The CH3OH column density distributions are consistent with isotropic, uniform outflow from the nucleus, with no evidence for extended sources of CH3OH in the coma. The radial profiles show a significant drop within a few thousand kilometers of the nucleus, falling from about 60 to 20 K between and 2500 km on June 28, whereas on June 29, Trot fell from about 120 to 40 K between ρ = 0 km and 1000 km. The observed Trot behavior is interpreted primarily as a result of variations in the coma kinetic temperature due to adiabatic cooling of the outflowing gas, as well as radiative cooling of the CH3OH rotational levels. Our excitation model shows that radiative cooling is more important for the transitions (at 338 GHz) than for the transitions (at 252 GHz), resulting in a strongly sub-thermal distribution of levels in the band at . For both bands, the observed temperature drop with distance is less steep than predicted by standard coma theoretical models, which suggests the presence of a significant source of heating in addition to the photolytic heat sources usually considered. [ABSTRACT FROM AUTHOR]

IRAS 19312+1950 is a peculiar object that has eluded firm characterization since its discovery, with combined maser properties similar to an evolved star and a young stellar object (YSO). To help determine its true nature, we obtained infrared spectra of IRAS 19312+1950 in the range 5–550 μm using the Herschel and Spitzer space observatories. The Herschel PACS maps exhibit a compact, slightly asymmetric continuum source at 170 μm, indicative of a large, dusty circumstellar envelope. The far-IR CO emission line spectrum reveals two gas temperature components: ≈0.22 M⊙ of material at 280 ± 18 K, and ≈1.6 M⊙ of material at 157 ± 3 K. The O i 63 μm line is detected on-source but no significant emission from atomic ions was found. The HIFI observations display shocked, high-velocity gas with outflow speeds up to 90 km s−1 along the line of sight. From Spitzer spectroscopy, we identify ice absorption bands due to H2O at 5.8 μm and CO2 at 15 μm. The spectral energy distribution is consistent with a massive, luminous (∼2 × 104L⊙) central source surrounded by a dense, warm circumstellar disk and envelope of total mass ∼500–700 M⊙, with large bipolar outflow cavities. The combination of distinctive far-IR spectral features suggest that IRAS 19312+1950 should be classified as an accreting, high-mass YSO rather than an evolved star. In light of this reclassification, IRAS 19312+1950 becomes only the fifth high-mass protostar known to exhibit SiO maser activity, and demonstrates that 18 cm OH maser line ratios may not be reliable observational discriminators between evolved stars and YSOs. [ABSTRACT FROM AUTHOR]

We report observations at millimeter and submillimeter wavelengths of comet C/2009 P1 (Garradd) from 2011 December 28 to 2012 April 24, using the Arizona Radio Observatory submillimeter telescope (SMT) and the James Clerk Maxwell Telescope (JCMT). Garradd is a dynamically young long-period comet from the Oort Cloud, with a periodicity of 127,000 yr, that reached perihelion on 2011 December 23 (at = 1.55 AU and Δ = 20.1 AU) and made its closest approach to the Earth on 2012 March 05 (at = 1.84 AU and Δ = 1.26 AU). We obtained gas production rates, and molecular abundances relative to water for HCN, ortho-, CS, CO and . A rotational temperature, K, was determined by observing multiple methanol lines with the JCMT. By averaging the abundance ratio relative to water from the SMT and the JCMT we derive: CO: 7.03%± 1.84%, HCN: 0.04% ± 0.01%, o-: 0.14% ± 0.03% as a parent molecule (and 0.28% ± 0.06% as an extended source), CS: 0.03% ± 0.01% and : . We concluded that Garradd is normal in , depleted in HCN, o- and CS and slightly enriched in CO with respect to typically observed cometary mixing ratios. We also studied the temporal evolution of HCN and CO and find that the production of HCN has a trend similar to water (but with short-term variation), with a decrease after perihelion, while that of CO shows contrary behavior: remaining constant or increasing after perihelion. [ABSTRACT FROM AUTHOR]