Photochemistry Archives

Three independent reductions of the NIRCam F322W2 and F444W data agree within their uncertainties The top panel shows the F322W2 and F444W transmission spectra, as reduced using the Pegasus, Eureka, and tshirt pipelines, plotted with their associated 1 σ uncertainties using constant 0.015µm-wide spectral bins. All of the F322W2 spectra have been offset down by 163 ppm to correct for a bias offset in the F322W2 transit depths compared to the F444W and Spitzer data (see Appendix B.3). All three reductions agree on the shape of the transmission spectrum and show features due to H2O (2.5–3.2µm), CH4 (3.2–3.5µm), SO2 (3.9–4.1µm), and CO2 (2.6–2.9µm and 4.2–4.5µm). The absorption cross sections of the prominent species in this wavelength range, many of which are visually identifiable in the bottom panel. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Sulfur Dioxide and Other Molecular Species in the Atmosphere of the Sub-Neptune GJ 3470 b

by Keith CowingJune 11, 2024June 11, 2024

We report observations of the atmospheric transmission spectrum of the sub-Neptune exoplanet GJ 3470 b taken using the Near-Infrared Camera (NIRCam) on JWST. Combined with two archival HST/WFC3 transit observations […]

Weighting function distribution for nadir and limb viewing geometries for the 2017 observation. Beam locations were placed such that the top-of-atmosphere latitudes matched for both locations for each observation, taking into account Titan’s tilt. Weighting distributions are not coadded, as plotted, but calculated individually for each extraction region. Titan’s solid body radius (2575 km; dashed circle), top of atmosphere (1200 km above the surface; solid circle), and top-of-atmosphere latitudes are shown. The FWHM of the ALMA beam is denoted by the dashed ellipses. -- astro-ph.EP

Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Icy Worlds, Imaging & Spectroscopy, Mapping, Geodesy, Cartography, Bathymetry, Status Report, Titan

Variability in Titan’s Mesospheric HCN and Temperature Structure as Observed by ALMA

by Keith CowingFebruary 6, 2024February 6, 2024

The temperature structure of Titan’s upper atmosphere exhibits large variability resulting from numerous spatially and temporally irregular external energy sources, seasonal changes, and the influence of molecular species produced via […]

Ternary diagrams depicting the porosity levels required for selected ices to float on the ternary mixture. The light blue and pink diamond symbols indicate observed compositions of Titan’s northern and southern polar lakes, with diamond-shaped boxes showing the uncertainty (Poggiali et al., 2020). -- astro-ph.EP

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Saturn, Status Report, Titan

The Fate of Simple Organics on Titan’s Surface: A Theoretical Perspective

by Keith CowingJanuary 8, 2024January 8, 2024

Atmospheric photochemistry on Titan continuously transforms methane and nitrogen gases into various organic compounds.

Schematic diagram demonstrating interstellar ices within dark clouds made of molecular hydrogen being processed by photochemistry involving the production of electronically excited water and radiation chemistry involving the production of ionized water and secondary electrons. This work focuses on the interaction depicted in the second of the two CRs (blue lines) in which a CR interacts in the ice mantle to produce secondary electrons. Reproduced from Ref. 4. Copyright 2019, The Royal Society of Chemistry. -- astro-ph.HE

Astrochemistry, Status Report

The Role of Low-energy (< 20 eV) Secondary Electrons in the Extraterrestrial Synthesis of Prebiotic Molecules

by Keith CowingDecember 6, 2023December 6, 2023

We demonstrate for the first time that Galactic cosmic rays with energies as high as 1e10 eV can trigger a cascade of low-energy (< 20 eV) secondary electrons that could […]

Comparison of measured and simulated absorbances of C2H6 (top) and C2H2 (bottom) for a spectral resolution of 0.45 cm-1 in the case of the H2:CH4:N2 gas mixture after 24 hr of irradiation at 473 K. The simulated spectra were obtained following the procedure described in Section 2.2. -- astro-ph.EP

Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Experimental Investigation of the Photochemical Production of Hydrocarbons in Warm Gas Giant Exoplanet Atmospheres

by Keith CowingOctober 19, 2023October 19, 2023

In warm (equilibrium temperature <1000 K) gas giant exoplanet atmospheres, the observation of trace species in abundances deviating from thermochemical equilibrium predictions could be used as an indicator of disequilibrium […]

The left panel shows the synthetic transmission spectra of the evening and morning limbs of WASP-39b with a resolution of R = 300. The atmospheric structure and chemical composition are based on 2D VULCAN, incorporating temperature and wind profiles obtained from the Exo-FMS GCM. The models excluding horizontal transport are labelled 1D for comparison. The right panel shows the morning-evening averaged transmission spectra when assuming different atmospheric metallicities within 2D VULCAN. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Status Report

Day-night Transport Induced Chemistry And Clouds On WASP-39b I: Gas-phase Composition

by Keith CowingJune 14, 2023June 14, 2023

JWST has recently detected the first robust photochemical product on an exoplanet: sulfur dioxide (SO2) on WASP-39b (Rustamkulov et al. 2023; Alderson et al. 2023; Tsai et al. 2023b).

Van Krevelen diagrams of a) 2 month old sample, b) 1.8 year old sample, c) 3.5 year old sample. The intensity of the points is given by the color code ranging from blue (lowest abundance) to red (highest abundance). Mass spectra of five different families present in the sample are given for the d) 2 month old sample, e) 1.8 year old sample, f) 3.5 year old sample. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Status Report, Titan

Humid Evolution of Haze in the Atmosphere of Super-Earths in the Habitable Zone

by Keith CowingJune 2, 2023June 2, 2023

Photochemical hazes are expected to form and significantly contribute to the chemical and radiative balance of exoplanets with relatively moderate temperatures, possibly in the habitable zone of their host star.

Two example cases comparing the outputs of one of the NN models with the corresponding TEA outputs. Left: Case where the NN’s predictions closely match the outputs of TEA, at a temperature of ∼1053 K, log C/H of -3.57, log N/H of -4.17, and log O/H of -3.31 over the full range of pressures considered in Table 1. Right: Case where the NN performs less accurately, at a temperature of ∼2112 K, M/H of 2.5, and C/O of 0.9 (log C/H of -0.956, log N/H of -1.556, and log O/H of -0.910). Despite the less accurate performance, the NN’s predictions are within an order of magnitude of the true values except for H2O, CO2, and HCN at the lowest pressures. Only abundances ≥ 10−15 are shown for clarity. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Status Report

Towards 3D Retrieval of Exoplanet Atmospheres: Assessing Thermochemical Equilibrium Estimation Methods

by Keith CowingApril 4, 2023April 4, 2023

Characterizing exoplanetary atmospheres via Bayesian retrievals requires assuming some chemistry model, such as thermochemical equilibrium or parameterized abundances. The higher-resolution data offered by upcoming telescopes enables more complex chemistry models […]

Astrochemistry, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Imaging & Spectroscopy, Press Release, TRAPPIST-1

Exploring Nitrous Oxide As An Indication Of Life

by Keith CowingFebruary 5, 2023February 5, 2023

Researchers supported by NASA have used a model to predict the concentration of nitrous oxide (N2O) in the atmosphere of planets over a range of conditions. On Earth, N2O can […]

Astronomy & Telescopes, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Press Release

Direct Evidence of Photochemistry In An Exoplanet Atmosphere

by Keith CowingNovember 21, 2022November 21, 2022

Photochemistry is a fundamental process of planetary atmospheres that is integral to habitability, atmospheric composition and stability, and aerosol formation. However, no unambiguous photochemical products have been detected in exoplanet […]

Photochemistry

Sulfur Dioxide and Other Molecular Species in the Atmosphere of the Sub-Neptune GJ 3470 b

Variability in Titan’s Mesospheric HCN and Temperature Structure as Observed by ALMA

The Fate of Simple Organics on Titan’s Surface: A Theoretical Perspective

The Role of Low-energy (< 20 eV) Secondary Electrons in the Extraterrestrial Synthesis of Prebiotic Molecules

Experimental Investigation of the Photochemical Production of Hydrocarbons in Warm Gas Giant Exoplanet Atmospheres

Day-night Transport Induced Chemistry And Clouds On WASP-39b I: Gas-phase Composition

Humid Evolution of Haze in the Atmosphere of Super-Earths in the Habitable Zone

Towards 3D Retrieval of Exoplanet Atmospheres: Assessing Thermochemical Equilibrium Estimation Methods

Exploring Nitrous Oxide As An Indication Of Life

Direct Evidence of Photochemistry In An Exoplanet Atmosphere

How A Deep-sea Protein Adapts To An Extreme Environment

Fingerprints Inside Our Sun Could Reveal If It Once Swallowed A Planet

Climates Of Gl 514 b

Cosmic Radiation at Flight Altitudes Rises When the Sun Is Less Active

The History Of Enzyme Evolution Embedded In Metabolism