Photochemical haze Archives

[LEFT] Haze mass mixing ratio, q1 [g g−1 ] (left column), and haze particle size , rh [nm] (right column), for the short formation timescale simulation at 10−5 bar (top row), 10−4 bar (second row), 10−3 bar (third row) and 10−2 bar (bottom row) pressure levels. The sub-stellar point is located at (0◦, 0◦). {RIGHT} same as LEFT but for the long haze formation timescale. -- astro-ph.EP

Three Dimensional Temporal Evolution Of Photochemical Haze In Exoplanet Atmospheres I. Description And Test Application To HD 189733b

by Keith CowingJune 20, 2026June 20, 2026

The formation and global spatial distribution of photochemically produced haze particles remain a key process in exoplanet atmospheres for understanding their observed properties. We aim to develop a flexible haze […]

Transmission spectrum of GJ 1214b using the 5% CH4-derived haze sample atmospheric composition. The sample from K84, G18/C23 C/O = 1 sample, and H24’s sample at 300 K are overplotted for reference. We include the observations from L. Kreidberg et al. (2014); E. M. R. Kempton et al. (2023b); E. Schlawin et al. (2024) with offsets for comparisons between models. The error bars account for 1σ uncertainties in the observations. Top: Spectra from 0.5 to 8 µm, where there are large differences in the resulting transmission spectrum between the sample and previous literature optical constants. Our samples pre- and post-irradiation produce largely flat spectra. Bottom: Spectra from 2 to 3 µm. We see slight changes between our preand post-irradiation transmission spectra, where our hazes are letting gaseous CO2 found in the simulated atmosphere to be more or less visible. -- astro-ph.EP

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

Ultraviolet Radiation Effects on the Optical Properties of Water-Dominated Exoplanet Hazes

by Keith CowingJune 8, 2026June 8, 2026

Temperate sub-Neptune and terrestrial exoplanets could contain large inventories of water in various phases, such as water-dominated atmospheres or even oceans. Observations have shown that many exoplanets, including water worlds, […]

Transit spectrum of K2-18 b based on the detection with Kepler (Montet et al. 2015) and characterisation with HST/WFC (Benneke et al. 2017), Spitzer (Benneke et al. 2019), JWST/NIRISS &/NIRSpec (Madhusudhan et al. 2023; Schmidt et al. 2025) and JWST/MIRI (Madhusudhan et al. 2025; Liu et al. 2025). Different panels compare different pipelines for the NIRISS and NIRSpec analyses. -- astro-ph.EP

Astrochemistry, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Icy Worlds, Imaging & Spectroscopy, Status Report

The Atmosphere Of K2-18 b: The Role Of Hazes, Clouds And Photoelectrons

by Keith CowingMarch 30, 2026March 30, 2026

The atmospheric characterisation of temperate exoplanets is becoming accessible with JWST, providing a critical connection between Solar System planets and the more commonly observed hot-Jupiters.

Mars-like Exoplanet -- Grok via Astrobiology.com

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Oxygenated False Positive Biosignatures in Mars-like Exoplanet Atmospheres

by Keith CowingMarch 14, 2026March 14, 2026

Oxygen is a well-studied biosignature. Studying potential abiotic pathways for O2 build-up in exoplanet atmospheres is essential for evaluating whether the detection of O2 would constitute a biosignature detection on […]

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

Photochemical Haze Formation on Titan and Uranus: A Comparative Review

by Keith CowingAugust 15, 2025August 15, 2025

The formation and evolution of haze layers in planetary atmospheres play a critical role in shaping their chemical composition, radiative balance, and optical properties.

Encircled in purple stratospheric haze, Saturn's largest moon, Titan, appears as a softly glowing sphere in this colorized image taken on July 3, 2004, one day after Cassini's first flyby of that moon. Titan has a dense atmosphere composed primarily of nitrogen with a few percent methane. -- NASA Larger image

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Gas Giants, Imaging & Spectroscopy, Status Report, Titan, Venus

Measurement of Photochemical Haze Refractive Indices and Hygroscopicity: Influence of CO2 in CH4/H2S/N2 Mixtures

by Keith CowingJune 10, 2025June 10, 2025

Atmospheric organic hazes are widespread across various planetary bodies and have significant effects on both the surface and atmosphere. In this study, we investigate the optical and hygroscopic properties of […]

Summary of the haze properties assumed in the simulations. The left panel shows number density and mean radius of the haze distribution that was used as input in the GCM simulations. The middle panel shows the differential optical depth for soot (solid) and tholin (dashed) hazes at 1 µm (representative for the incoming starlight) and 8 µm (representative for the outgoing thermal radiation) for the nominal haze opacity case. The pressure levels where the optical depth reaches 0.01 (circle), 0.1 (star), and 1 (square) are highlighted. For soot at 1 µm, the optical depth reaches 0.01 at a pressure of 6 · 10−7 bar, outside the pressure range shown. The right panel shows the wavelength-averaged single scattering albedo weighted by the stellar flux. For the “maximally reflective” case, the optical depth is identical to the soot case, but the single scattering albedo is fixed to 0.9999. -- astro-ph.EP

Astrochemistry, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Habitable Zones, Ice Giant, Icy Worlds, Imaging & Spectroscopy, Status Report

The Radiative Effects of Photochemical Hazes on the Atmospheric Circulation and Phase Curves of Sub-Neptunes

by Keith CowingMarch 31, 2025May 12, 2025

Measuring the atmospheric composition of hazy sub-Neptunes like GJ 1214 b through transmission spectroscopy is difficult because of the degeneracy between mean molecular weight and haziness.

Phase folded JWST/MIRI observations of TRAPPIST-1 b. a. Phase-folded light curve of the secondary eclipse of TRAPPIST-1 b at 12.8 µm, derived from the observations of 5 eclipses as part of GTO 1279 observations. b. Phase-folded light curve of the secondary eclipse of TRAPPIST-1 b at 15 µm, derived from re-analyses of the observations of 5 eclipses as part of GTO 1177. These figures are derived from the “fiducial analysis” described in the Methods. Blue dots corresponds the corrected flux at the original time sampling, black dots shows the 10min binned corrected flux with an error equal to the standard deviation of the points within the bin, and the red curve show the eclipse model. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, TRAPPIST-1

Combined Analysis of the 12.8 and 15 μm JWST/MIRI Eclipse Observations of TRAPPIST-1 b

by Keith CowingDecember 18, 2024December 18, 2024

The first JWST/MIRI photometric observations of TRAPPIST-1 b allowed for the detection of the thermal emission of the planet at 15 μm, suggesting that the planet could be a bare […]

The weighted abundance of CO calculated using Equation 1 has been shown as a heat map as a function of C/O and Kzz in each panel. Each row corresponds to a different Teq value from 1100 K to 600 K from top to bottom. Each column correspond to a different Tint value between 30 K and 500 K from left to right. Note that the C/O has been shown relative to the assumed solar value of 0.458 in this plot. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Gas Giants, Habitable Zones, Ice Giant, Imaging & Spectroscopy, Neptune, Status Report

Effects of Planetary Parameters on Disequilibrium Chemistry in Irradiated Planetary Atmospheres: From Gas Giants to Sub-Neptunes

by Keith CowingOctober 23, 2024May 12, 2025

A primary goal of characterizing exoplanet atmospheres is to constrain planetary bulk properties, such as their metallicity, C/O ratio, and intrinsic heat. However, there are significant uncertainties in many aspects […]

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.

Photochemical haze

Three Dimensional Temporal Evolution Of Photochemical Haze In Exoplanet Atmospheres I. Description And Test Application To HD 189733b

Ultraviolet Radiation Effects on the Optical Properties of Water-Dominated Exoplanet Hazes

The Atmosphere Of K2-18 b: The Role Of Hazes, Clouds And Photoelectrons

Oxygenated False Positive Biosignatures in Mars-like Exoplanet Atmospheres

Photochemical Haze Formation on Titan and Uranus: A Comparative Review

Measurement of Photochemical Haze Refractive Indices and Hygroscopicity: Influence of CO2 in CH4/H2S/N2 Mixtures

The Radiative Effects of Photochemical Hazes on the Atmospheric Circulation and Phase Curves of Sub-Neptunes

Combined Analysis of the 12.8 and 15 μm JWST/MIRI Eclipse Observations of TRAPPIST-1 b

Effects of Planetary Parameters on Disequilibrium Chemistry in Irradiated Planetary Atmospheres: From Gas Giants to Sub-Neptunes

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

PJ Harvey Announces New Song “Voyager”

Fifty Years after Viking: The Promise of Solar System Microbiology and Microbial Ecology

Characterising Transiting Exoplanets At Long Orbital Period: Lessons Learned For PLATO From 10 Years Of Monitoring The HIP41378 System

Implications Of Self-consistent H2O Ice Optical Constants On Radiative Transfer Models Of Disks

The GAPS Programme at TNG LXXIV. A Reanalysis Of The Planetary Systems TOI-1272 And TOI-1694 With HARPS-N And Retraction Of The Planetary Interpretation Of TOI-1272 c