NIRSpec Archives

Spatial distributions of MnS (left) and Na2S (right) clouds as a function of longitude, averaged over all latitudes, and pressure in our cloudy SPARC/MITgcm model. The color mapping represents the mass mixing ratio of the cloud particle, with the same scaling in each panel. -- astro-ph.EP

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

A Panchromatic Characterization Of The Evening And Morning Atmosphere Of WASP-107 b

by Keith CowingJuly 28, 2025July 28, 2025

Limb-resolved transmission spectroscopy has the potential to transform our understanding of exoplanetary atmospheres. By separately measuring the transmission spectra of the evening and morning limbs, these atmospheric regions can be […]

Illustration of the range of possible internal compositions for temperate sub-Neptunes like K2-18 b, and a roadmap to characterize them through atmospheric observations. A liquid-water ocean separating the atmosphere from the interior necessarily implies a small atmosphere, which may be composed of either H2 or heavier molecules. In contrast, a massive atmosphere is expected to be well-mixed with the volatile envelope underneath. We propose characterizing such massive envelopes along two principal axes: the H2-to-H2O ratio and the metallicities defined by carbon, nitrogen, and sulfur. In a standard H2-dominated envelope, the oxygen abundance tracks that of C, N, and S with the solar abundance ratio. In a mixed or steam-rich envelope, oxygen (and thus H2O) is more abundant; in a soot-rich envelope, it is less so. Nitrogen and sulfur may be depleted relative to carbon due to preferential partitioning into the mantle or core. The existence of a water-dominated layer between the envelope and the rocky interior remains uncertain, but is retained here as a possibility. Regardless of envelope composition, water may condense in the atmospheres of K2-18 b and cooler sub-Neptunes, rendering direct H2O measurements from transmission spectra unreliable as diagnostics of the bulk composition. Instead, detecting and quantifying a suite of gases, such as CH4, CO2, CO, NH3, and SO2, and their relative abundances offers a more robust pathway to distinguish among envelope compositions, physical states, and the potential presence of a liquid-water ocean. -- astro-ph.EP

Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Icy Worlds, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

A Water-rich Interior In The Temperate Sub-Neptune K2-18 b Revealed By JWST

by Keith CowingJuly 18, 2025July 18, 2025

Temperate sub-Neptunes Are Compelling Targets For Detecting Liquid-water Oceans Beyond The Solar System. If water-rich and lacking massive hydrogen-helium envelopes, these planets could sustain liquid layers beneath their atmospheres despite […]

(top) The JWST spectrum of Cha 1107-7626 taken with NIRSpec-PRISM (green) and MIRI-LRS (blue). Overplotted are the ISPI and Spitzer photometric points from Luhman et al. (2008). (bottom) The spectral data plotted above, zoomed-in on two spectral features in the mid-IR, which we identify as methane and ethylene (see Section 5). -- astro-ph.EP

Astrochemistry, Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Interstellar, Status Report

Detection Of Hydrocarbons In The Disk Around An Actively-Accreting Planetary-Mass Object

by Keith CowingMay 21, 2025May 21, 2025

We present the 0.6–12-micron spectrum of Cha 1107-7626, a 6-10 Jupiter-mass free-floating object in the ∼2 Myr-old Chamaeleon-I star-forming region, from observations with the NIRSpec and MIRI instruments onboard the […]

Transmission spectra of K2-18 b from exoTEDRF (blue), JExoRES (black), SPARTA (orange) and Eureka! (green). For NIRISS and NIRSpec, faded points show higher resolution (R=100 and 200, respectively) spectra, and solid colors are binned for clarity. Smaller panels show error-normalized differences relative to exoTEDRF. The JExoRES spectra used different binning and are interpolated in the difference panels. -- astro-ph.EP

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, Venus

Insufficient Evidence For DMS And DMDS In The Atmosphere Of K2-18 b

by Keith CowingMay 20, 2025September 18, 2025

Recent JWST observations of the temperate sub-Neptune K2-18 b have been interpreted as suggestive of a liquid water ocean with possible biological activity. Signatures of DMS and DMDS have been […]

Contributions of molecules in the JWST MIRI range for the transmission spectrum of K2-18 b, assuming 1% CO2 and CH4, and 10−5 by volume for each of DMS, diethyl sulfide, methacrylonitrile, trans-2-pentene, 2-butene and propyne. -- astro-ph.EP

Astrochemistry, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

A Systematic Search for Trace Molecules in Exoplanet K2-18 b

by Keith CowingMay 16, 2025May 16, 2025

The first transmission spectrum of the habitable-zone sub-Neptune K2-18 b with JWST has opened a new avenue for atmospheric characterisation of temperate low-mass exoplanets.

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

Hot sub-Neptune Exoplanet TOI-421 b NIRISS/NIRSpec Transmission Spectrum

by Keith CowingMay 6, 2025

This is a transmission spectrum captured by the NASA/ESA/CSA James Webb Space Telescope that reveals the presence of water (H2O) and the possible presence of sulfur dioxide (SO2) and carbon […]

Breakdown of our best-fit model for the transit spectrum of TOI-270 d. Absorption bands of CH4, CO2 are clearly visible and one isolated absorption band of CS2 contributes at 4.6 µm. The impact of water, CO and SO2 on the spectrum is negligible. The model has been smoothed for visual clarity. astro-ph.EP

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

Evidence For Sulfur Chemistry In The Atmosphere Of The Warm Sub-Neptune TOI-270 d

by Keith CowingApril 18, 2025April 18, 2025

Context: Recent JWST measurements allow access to the near-infrared spectrum of the sub-Neptune TOI-270 d, for which two different interpretations, a high-metallicity miscible envelope and a lower metallicity hycean world, […]

Spectral maps illustrating the distribution in the band centers, depths, and areas for (top) Europa’s 1.5 µm band (1.48 – 1.74 µm) -- astro-ph.EP

Analog Studies, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Caves, Craters, Mountains, Subsurface, Lava Tubes, Cryobiology, Europa, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Jupiter, Mapping, Geodesy, Cartography, Bathymetry, Status Report, Water/Hycean Worlds & Oceanography

JWST Reveals Spectral Tracers of Recent Surface Modification on Europa

by Keith CowingApril 8, 2025April 8, 2025

Europa has been modified by a variety of geologic processes, exposing internally-derived materials that are heavily irradiated by charged particles trapped in Jupiter’s magnetosphere.

At the left, an enhanced-color image of Neptune from NASA’s Hubble Space Telescope. At the right, that image is combined with data from NASA’s James Webb Space Telescope. The cyan splotches, which represent auroral activity, and white clouds, are data from Webb’s Near-Infrared Spectrograph (NIRSpec), overlayed on top of the full image of the planet from Hubble’s Wide Field Camera 3. - STSCI

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Ice Giant, Icy Worlds, Imaging & Spectroscopy, Neptune, People Of Astrobiology, Press Release, Radiation, Space Weather & Heliophysics

Webb Space Telescope Captures Neptune’s Auroras For First Time

by Keith CowingApril 4, 2025May 12, 2025

For the first time, NASA’s James Webb Space Telescope has captured bright auroral activity on Neptune. Auroras occur when energetic particles, often originating from the Sun, become trapped in a […]

This artist’s concept shows what the isolated planetary-mass object SIMP 0136 could look like based on recent observations from NASA’s James Webb Space Telescope and previous observations from Hubble, Spitzer, and numerous ground-based telescopes. Researchers used Webb’s NIRSpec (Near-Infrared Spectrograph) and MIRI (Mid-Infrared Instrument) to measure subtle changes in the brightness of infrared light as the object completed two 2.4-hour rotations. -- NASA, ESA, CSA, and Joseph Olmsted (STScI)

Astronomy & Telescopes, Atmospheres, Climate, Weather, Brown Dwarfs, Exoplanets, -moons, -comets, Gas Giants, Icy Worlds, Imaging & Spectroscopy, Press Release

Webb Exposes Complex Atmosphere of Free-Floating Super-Jupiter SIMP 0136

by Keith CowingMarch 4, 2025March 4, 2025

An international team of researchers has discovered that previously observed variations in brightness of a free-floating planetary-mass object known as SIMP 0136 must be the result of a complex combination […]