Ground-based Atmospheric Characterization of Super-Earth L 98-59 d at High Spectral Resolution

Abstract

Atmospheric characterization of exoplanets using ground-based high-resolution transmission spectroscopy has traditionally focussed on large and close-in planets, such as hot Jupiters. In this work, we aim to extend this technique to smaller and more temperate planets by studying the atmospheric composition of the temperate super-Earth planet L 98-59 d ($\sim$$1.5{\mathrm{R}}_{\oplus }$; $\sim$$1.9{\mathrm{M}}_{\oplus }$). Using high-resolution transmission spectra obtained using IGRINS on the Gemini-South telescope, we demonstrate the feasibility for atmospheric characterization of super-Earths using ground-based facilities, and confirm the previous tentative JWST inference of hydrogen sulfide (H2S) in the atmosphere of L 98-59 d at $\lesssim$3.9$\sigma$ ($B\sim 390$). This is the first ground-based inference of a molecular species in the atmosphere of a super-Earth planet, and reveals the sensitivity of spectrographs on 8m-class telescopes to the atmospheric characterization of such planets. By exploring a grid of atmospheric models, we find that the data favors a cloud-free atmosphere with an abundance of H2S corresponding to $\sim$1-10$\times$ solar metallicity. We additionally place constraints on the atmospheric abundances of other molecular species. Assuming cloud-free models, super-solar abundances for CH4 and NH3 are ruled out at 3.6$\sigma$ and $4.6\sigma$, respectively. Our results are consistent with previous suggestions that L 98-59 d is a super-Earth with possible disequilibrium production of H2S driven by volcanic outgassing from the surface. Future studies combining multiple observations with different facilities may be able to further constrain the atmospheric composition of this planet. This work underscores the promise of atmospheric characterization of super-Earth exoplanets using high-resolution spectroscopy with ground-based facilities.

Accepted for publication in MNRAS 01 March 2026

References in corpus (41)

• The Transiting Exoplanet Survey Satellite
• Most 1.6 Earth-Radius Planets are not Rocky
• Density, not radius, separates rocky and water-rich small planets orbiting M dwarf stars
• Photochemically-produced SO${}_2$ in the atmosphere of WASP-39b
• ExoMol molecular line lists - XVI: The rotation-vibration spectrum of hot H${}_2$S
• Detection of Fe I in the atmosphere of the ultra-hot Jupiter WASP-121b, and a new likelihood-based approach for Doppler-resolved spectroscopy
• A solar C/O and sub-solar metallicity in a hot Jupiter atmosphere
• Five carbon- and nitrogen-bearing species in a hot giant planet's atmosphere
• High Tide or Riptide on the Cosmic Shoreline? A Water-Rich Atmosphere or Stellar Contamination for the Warm Super-Earth GJ~486b from JWST Observations
• Atmospheric Reconnaissance of TRAPPIST-1 b with JWST/NIRISS: Evidence for Strong Stellar Contamination in the Transmission Spectra
• Habitability and Biosignatures of Hycean Worlds
• A JWST transmission spectrum of a nearby Earth-sized exoplanet
• The L 98-59 System: Three Transiting, Terrestrial-Sized Planets Orbiting a Nearby M-dwarf
• GENESIS: New Self-Consistent Models of Exoplanetary Spectra
• Photoevaporation vs. core-powered mass-loss: model comparison with the 3D radius gap
• Warm terrestrial planet with half the mass of Venus transiting a nearby star
• Double Trouble: Two Transits of the Super-Earth GJ 1132 b Observed with JWST NIRSpec G395H
• Relative abundance constraints from high-resolution optical transmission spectroscopy of WASP-121b, and a fast model-filtering technique for accelerating retrievals
• The Roasting Marshmallows Program with IGRINS on Gemini South I: Composition and Climate of the Ultra Hot Jupiter WASP-18 b
• Aurora: A Generalised Retrieval Framework for Exoplanetary Transmission Spectra
• Marvel analysis of the measured high-resolution rovibrational spectra of H2S
• HyDRA-H: Simultaneous Hybrid Retrieval of Exoplanetary Emission Spectra
• Seeing above the Clouds with High Resolution Spectroscopy
• LHS 1140 b is a potentially habitable water world
• Robustness Measures for Molecular Detections using High-Resolution Transmission Spectroscopy of Exoplanets
• Atmospheric retrievals suggest the presence of a secondary atmosphere and possible sulfur species on L 98-59 d from JWST NIRSpec G395H transmission spectroscopy
• Arid or Cloudy: Characterizing the Atmosphere of the super-Earth 55 Cancri e using High-Resolution Spectroscopy
• Black Mirror: The impact of rotational broadening on the search for reflected light from 51 Pegasi b with high resolution spectroscopy
• A Near-Infrared Chemical Inventory of the Atmosphere of 55 Cancri e
• JWST Reveals CH${}_4$, CO${}_2$, and H${}_2$O in a Metal-rich Miscible Atmosphere on a Two-Earth-Radius Exoplanet
• High-Resolution Transmission Spectroscopy of the Terrestrial Exoplanet GJ 486b
• Hubble WFC3 Spectroscopy of the Terrestrial Planets L~98-59~c \& d: No Evidence for a Clear Hydrogen Dominated Primary Atmosphere
• Characterising Atmospheres of Cloudy Temperate Mini-Neptunes with JWST
• The hot Neptune WASP-166 b with ESPRESSO III: A blue-shifted tentative water signal constrains the presence of clouds
• Prebiosignature Molecules Can Be Detected in Temperate Exoplanet Atmospheres with JWST
• The sulphur species in hot rocky exoplanet atmospheres
• IGRINS observations of WASP-127 b: H${}_2$O, CO, and super-Solar atmospheric metallicity in the inflated sub-Saturn
• Self-limited tidal heating and prolonged magma oceans in the L 98-59 system
• On the Effect of Stellar Activity on Low-resolution Transit Spectroscopy and the Use of High Resolution as Mitigation
• Retrieving day- and nightside atmospheric properties of the ultra-hot Jupiter TOI-2109b. Detection of Fe and CO emission lines and evidence for inefficient heat transport
• Exoplaneteers Keep Overestimating Sigma Significances

Cited by in corpus (1)

• A Validated Low-to-Intermediate Mass Planetary Interior Structure Model and New Mass-Radius Relations