MIRI Archives

The mid-infrared transmission spectrum of TOI-270 d obtained with the JWST MIRI LRS instrument and the JExoRES pipeline. The data points with error bars (in dark red) show the observed spectrum. The horizontal error bars correspond to the spectral bin width. The dark blue curve denotes the median retrieved spectral fit to this MIRI dataset using the canonical retrieval discussed in Section 3.2, while the two lighter shaded regions denote the 1σ and 2σ intervals. The yellow points denote the binned median model. -- astro-ph.EP

The Mid-Infrared Transmission Spectrum of the Temperate Sub-Neptune TOI-270 d

by Keith CowingJuly 8, 2026July 7, 2026

[astro-ph.EP] Observations of temperate sub-Neptunes with JWST have ushered in a new era for atmospheric characterization of small exoplanets.

Integrated MIRI-MRS spectrum of HK Tau A (top) and B (bottom) in grey, with the black line representing the continuum baseline. In the top panel, the insets zoom into wavelength regions where molecular emission from 12CO, H2O, 12CO2 , and H2 is visible. In the bottom panel, the shaded bands in the indicate the main ices absorption regions. H2 rotational lines are marked with blue ticks, and gas emission features are labelled where present. -- astro-ph.EP

Astrochemistry

MINDS: Complementary Inclinations In The Binary Ssystem HK Tau Reveal Gas- And Ice-phase Chemistry

by Keith CowingJuly 7, 2026July 7, 2026

[astro-ph.EP] HK Tau is a roughly equal mass pre-main sequence binary system consisting of a low-inclination primary (57 deg) and an edge-on (83 deg) secondary. We present JWST/MIRI observations targeting […]

Continuum-subtracted emissivity of 3I/ATLAS in the 6-7 µm region in black, compared to a set of reference spectra which are described in the main text.

Comets and Asteroids

The Dust Mineralogy of Interstellar Comet 3I/ATLAS from JWST/MIRI Observations

by Keith CowingJuly 3, 2026July 3, 2026

[astro-ph.EP] We present the first spectroscopic mineralogical analysis of the dust coma of an interstellar object (ISO) from JWST mid-infrared spectroscopy of 3I/ATLAS (3I).

NIRSpec average spectrum of Titan (black) compared with a radiative transfer calculation in which the surface albedo decreases smoothly with wavelength beyond 4.9 µm (red). The blue line shows the difference between the observed and synthetic spectra, shifted by 0.005 for clarity. The 5.11-µm absorption is clearly missing in the model. The small mismatch below 4.93 µm is due to a component of the non-LTE CO emission not included in the model. -- astro-ph.EP

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Icy Worlds, Imaging & Spectroscopy, Pluto, Status Report, Titan

An Unidentified Absorption Feature At 5.11 μm On The Surface Of Titan And Pluto From JWST Spectroscopy

by Keith CowingJune 12, 2026June 12, 2026

Titan possesses a thick N2-CH4 atmosphere that makes it difficult to study its surface spectroscopically. The chemical composition of the solid surface of Titan thus remains very uncertain.

Top: coma maps of H2O, CO2, and CH4, computed as the molecular column density from a pixel-by-pixel retrieval analysis for Observations 6, 15, and 6, respectively. The sunward and target velocity directions are denoted by the white arrows. The target centroids, computed as the photocenter in the median-stacked images (Figure 1), are marked with the black points. For H2O and CO2, the white contours correspond to emission levels of 50% and 20% relative to the maximum value and illustrate the slight antisunward extension of the respective comae. The contours are omitted in the CH4 panel, due to the poorer signal-to-noise ratio of the data. Bottom: corresponding median-stacked images across the continuum wavelengths within each fluorescence region. The H2O coma map shows a significant enhancement in the emission level at large nucleocentric distances relative to the dust continuum, indicating extended H2O production within the coma. -- The Astrophysical Journal Letters

Astrochemistry, Astronomy & Telescopes, Biogeochemical Cycles & Geobiology, Biophysics, Biosignatures & Paleobiology, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Interstellar, Press Release

Webb Detects Methane on Interstellar Comet 3I/ATLAS

by Keith CowingJune 2, 2026June 2, 2026

NASA’s James Webb Space Telescope has collected its first mid-infrared chemical fingerprint of an interstellar object during a recent revisit to comet 3I/ATLAS. The team’s results published recently in The […]

Transmission spectra of all cloud models for WASP-107b compared with the JWST NIRCam observations (black points). Dotted lines show small-particle models dominated by Rayleigh scattering (0.1 µm Na2S, KCl, MgSiO3); dashed lines are over-clouded models with suppressed molecular features (1 µm Na2S and MgSiO3); dot-dashed lines are under-clouded models with large features (10 µm Na2S; 5, 10 µm KCl; 10 µm MgSiO3). Solid lines indicate the three best-fit models: 5 µm Na2S (blue), 1 µm KCl (green), and 5 µm MgSiO3 (red). -- astro-ph.EP

Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Press Release

The Tale Of The 3 Planets: 3D Cloud Feedback Enhances The Spectral Diversity Of Warm Jupiters

by Keith CowingApril 30, 2026April 30, 2026

JWST has shown a large diversity in warm Jupiter spectra, despite only small variations in the planetary parameters. However, the main driver of this diversity remains unclear. We aim to […]

Artist's impression of the planet Epsilon Indi Ab, with water clouds atop its ammonia-dominated atmosphere. Credit E. C. Matthews, MPIA / T. Müller, HdA

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Gas Giants, Press Release

Astronomers Find An Exo-Jupiter, And It Seems To Have Clouds

by Keith CowingApril 23, 2026April 23, 2026

A team of astronomers led by Elisabeth Matthews at the Max Planck Institute for Astronomy (MPIA) has made a discovery that highlights the limits of most current models of exoplanet […]

The retrieved transmission spectrum using the results from the free retrieval plotted as a black line, along with the transmission data from NIRCam F322W2, F444W, and MIRI LRS plotted as black dots with 1 sigma error bars. Contributing absorption is plotted in various colors to show where gas species contribute the transmission spectrum. From the gas contributions we can see by eye that the absorption of CS2 matches the features at 4.6 µm and 6.5 µm nicely. --astro-ph.EP

Astrochemistry, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Gas Giants, Imaging & Spectroscopy, Status Report

The Identification of CS2 and Evidence for Carbon-Sulfur Chemical Coupling in a Warm Giant Exoplanet Atmosphere

by Keith CowingApril 17, 2026April 17, 2026

Transmission spectroscopy with the James Webb Space Telescope (JWST) is revealing growing chemical complexity in giant exoplanet atmospheres. Of particular interest is sulfur, which had essentially no observational constraints before […]

Best-fit white light (5.06–10.55 µm) curves of HD 3167 b’s secondary eclipse from our SPARTA (blue), Eureka! (red), and exoTEDRF (green) reductions. (Top) Binned raw white light fluxes. The best-fit full SPARTA model (with integration-level x decorrelation), Eureka, and exoTEDRF models are shown alongside the quadratic ramp component shown as dashed lines. (Middle) Binned fluxes after dividing by the best-fit systematics model for each reduction. Retrieved eclipse depths and uncertainties are shown on the right. (Bottom) Binned residuals of the best-fit full models. For all plots, Eureka!/exoTEDRF data are offset by 0.001/0.002 days for visual clarity. -- astro-ph.EP

Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Lava / magma ocean / Volcanic Worlds, Status Report

An Atmosphere On The Ultra-Short Period Super-Earth HD 3167 b

by Keith CowingApril 17, 2026April 17, 2026

‘Lava worlds’-Earth-sized planets hot enough (Teq >~ 1100 K) to melt their dayside silicate surfaces-have emerged as promising candidates for atmospheric detection and characterization. Thermal emission observations show an apparent […]

PSF-subtracted images of all targets. The observation subarray of each target is indicated. The first seven images are zoomed in to area of 11.0” × 11.0” for clearer view of the central regions. For the last three targets, the small size (4.4” × 4.4”) is due to the choice of the observation subarray. The location of the star PSF center is denoted by the white cross. Sources around LHS 1478, TOI-1468, and TOI-270 are labeled with letters, which are likely background sources. The arrow near HD 260655 indicates a low-S/N identification of possible close companion. We further examined this detection in Section 4.4. North is up and east is to the left. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, Stellar Cartography

A Search For Wide-orbit Planets Around M-dwarfs Using Deep MIRI 15-micron Images

by Keith CowingApril 12, 2026April 12, 2026

Wide-orbit (>10 AU) gas giant planets shape the architecture of planetary systems, yet their occurrence rate remains poorly constrained.

MIRI

The Mid-Infrared Transmission Spectrum of the Temperate Sub-Neptune TOI-270 d

MINDS: Complementary Inclinations In The Binary Ssystem HK Tau Reveal Gas- And Ice-phase Chemistry

The Dust Mineralogy of Interstellar Comet 3I/ATLAS from JWST/MIRI Observations

An Unidentified Absorption Feature At 5.11 μm On The Surface Of Titan And Pluto From JWST Spectroscopy

Webb Detects Methane on Interstellar Comet 3I/ATLAS

The Tale Of The 3 Planets: 3D Cloud Feedback Enhances The Spectral Diversity Of Warm Jupiters

Astronomers Find An Exo-Jupiter, And It Seems To Have Clouds

The Identification of CS2 and Evidence for Carbon-Sulfur Chemical Coupling in a Warm Giant Exoplanet Atmosphere

An Atmosphere On The Ultra-Short Period Super-Earth HD 3167 b

A Search For Wide-orbit Planets Around M-dwarfs Using Deep MIRI 15-micron Images

Laying Odds On The Potential For Martian Water

Assessing The Susceptibility Of Microalgae To Space Conditions Using Stratospheric Balloons

IMPRESS: A Planetary Penetrator Network for Astrobiology, Prospecting, and Exploration of Mars

Probing Primordial Chirality in the Matter Distribution

Small-Scale Mineral And Microbial Heterogeneities Near A Fumarole At The Furnas Hydrothermal Zone On The Azores