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Data availability and requirements relevant for the Ariel space mission and other exoplanet atmosphere applications

Katy L. Chubb, Séverine Robert, Clara Sousa-Silva, Sergei N. Yurchenko, Nicole F. Allard, Vincent Boudon, Jeanna Buldyreva, Benjamin Bultel, Athena Coustenis, Aleksandra Foltynowicz, Iouli E. Gordon, Robert J. Hargreaves, Christiane Helling, Christian Hill, Helgi Rafn Hrodmarsson, Tijs Karman, Helena Lecoq-Molinos, Alessandra Migliorini, Michaël Rey, Cyril Richard, Ibrahim Sadiek, Frédéric Schmidt, Andrei Sokolov, Stefania Stefani, Jonathan Tennyson, Olivia Venot, Sam O. M. Wright, Rosa Arenales-Lope, Joanna K. Barstow, Andrea Bocchieri, Nathalie Carrasco, Dwaipayan Dubey, Oleg Egorov, Antonio García Muñoz, Ehsan, Gharib-Nezhad, Leonardos Gkouvelis, Fabian Grübel, Patrick Gerard Joseph Irwin, Antonín Knížek, David A. Lewis, Matt G. Lodge, Sushuang Ma, Zita Martins, Karan Molaverdikhani, Giuseppe Morello, Andrei Nikitin, Emilie Panek, Miriam Rengel, Giovanna Rinaldi, Jack W. Skinner, Giovanna Tinetti, Tim A. van Kempen, Jingxuan Yang, Tiziano Zingales

TL;DR

This white paper addresses the data needs for exoplanet atmosphere characterisation with a focus on the Ariel mission (0.5–7.8 μm, $R \approx 100$). It inventories data types including molecular/atomic line lists, line shapes, cross-sections, CIA/continuum, aerosols, atmospheric chemistry, and UV photodissociation, evaluating current sources (e.g., ExoMol, HITRAN/HITEMP, NASA Ames, TheoReTS) and ongoing efforts. The work highlights gaps (notably high-temperature and UV/optical data, isotopologues, and advanced line-shape treatments) and proposes concrete paths, including lab measurements, theory enhancements, and standardized data platforms. A central outcome is the Ariel-data GitHub hub, designed to streamline requests, data linking, and interoperability among data-users and data-providers, thereby enabling robust, comparable atmospheric retrievals for Ariel and related studies.

Abstract

The goal of this white paper is to provide a snapshot of the data availability and data needs primarily for the Ariel space mission, but also for related atmospheric studies of exoplanets and brown dwarfs. It covers the following data-related topics: molecular and atomic line lists, line profiles, computed cross-sections and opacities, collision-induced absorption and other continuum data, optical properties of aerosols and surfaces, atmospheric chemistry, UV photodissociation and photoabsorption cross-sections, and standards in the description and format of such data. These data aspects are discussed by addressing the following questions for each topic, based on the experience of the "data-provider" and "data-user" communities: (1) what are the types and sources of currently available data, (2) what work is currently in progress, and (3) what are the current and anticipated data needs. We present a GitHub platform for Ariel-related data, with the goal to provide a go-to place for both data-users and data-providers, for the users to make requests for their data needs and for the data-providers to link to their available data. Our aim throughout the paper is to provide practical information on existing sources of data whether in databases, theoretical, or literature sources.

Data availability and requirements relevant for the Ariel space mission and other exoplanet atmosphere applications

TL;DR

This white paper addresses the data needs for exoplanet atmosphere characterisation with a focus on the Ariel mission (0.5–7.8 μm, ). It inventories data types including molecular/atomic line lists, line shapes, cross-sections, CIA/continuum, aerosols, atmospheric chemistry, and UV photodissociation, evaluating current sources (e.g., ExoMol, HITRAN/HITEMP, NASA Ames, TheoReTS) and ongoing efforts. The work highlights gaps (notably high-temperature and UV/optical data, isotopologues, and advanced line-shape treatments) and proposes concrete paths, including lab measurements, theory enhancements, and standardized data platforms. A central outcome is the Ariel-data GitHub hub, designed to streamline requests, data linking, and interoperability among data-users and data-providers, thereby enabling robust, comparable atmospheric retrievals for Ariel and related studies.

Abstract

The goal of this white paper is to provide a snapshot of the data availability and data needs primarily for the Ariel space mission, but also for related atmospheric studies of exoplanets and brown dwarfs. It covers the following data-related topics: molecular and atomic line lists, line profiles, computed cross-sections and opacities, collision-induced absorption and other continuum data, optical properties of aerosols and surfaces, atmospheric chemistry, UV photodissociation and photoabsorption cross-sections, and standards in the description and format of such data. These data aspects are discussed by addressing the following questions for each topic, based on the experience of the "data-provider" and "data-user" communities: (1) what are the types and sources of currently available data, (2) what work is currently in progress, and (3) what are the current and anticipated data needs. We present a GitHub platform for Ariel-related data, with the goal to provide a go-to place for both data-users and data-providers, for the users to make requests for their data needs and for the data-providers to link to their available data. Our aim throughout the paper is to provide practical information on existing sources of data whether in databases, theoretical, or literature sources.
Paper Structure (83 sections, 11 equations, 5 figures, 16 tables)

This paper contains 83 sections, 11 equations, 5 figures, 16 tables.

Table of Contents

  1. Introduction
  2. The Ariel space mission
  3. Atmospheric modelling and retrieval codes
  4. Paper structure
  5. Molecular/atomic line lists
  6. State of the art - Data availability
  7. Descriptions of molecular databases
  8. CaSDa
  9. ExoMol
  10. HITRAN and HITEMP
  11. NASA Ames database
  12. TheoReTS
  13. Laboratory spectroscopy measurements
  14. Experimental data for Solar System planets
  15. High-temperature experimental measurements
  16. ...and 68 more sections

Figures (5)

  • Figure 1: Comparison of $^{12}$CH$_4$ cross-sections at 296 K (left) and 1500 K (right) in the far and mid-infrared regions for different databases: MeCaSDa refcasda, TheoReTs TheoReTs, the ExoMol MM line list 24YuOwKe, HITRAN2020 2022JQSRT.27707949G and HITEMP HargreavesAJSS2020.
  • Figure 2: ExoMol Spectral Atlas 18TeYuxx.exo: Cross-sections of SO$_2$ computed with the ExoMol line ExoAmes jt635.
  • Figure 3: Measured spectra of CO$_2$ at different temperatures and pressures relevant to the atmosphere of Venus, from Stefani_2013.
  • Figure 4: Left: H$_2$ CIA coefficients at different pressures (8, 10, 12 bars) and room temperature (296 K). Right: H$_2$-He CIA coefficients at different pressures (10, 13 bars)) and temperatures (201, 299, 401 K). 24Vitali
  • Figure 5: The absorption spectra of 16.03 amagat of carbon dioxide at 243 and 323 K, demonstrating a number of CIA bands, recorded with PASSxS, after subtraction of the strong contributions of the $\nu_3$ fundamental band at 2350 cm$^{-1}$ and a weaker Fermi doublet ($\nu_3+\nu_1, \nu_3+2\nu_2$) around 3700 cm$^{-1}$, as well as contributions of the $^{16}$O$^{12}$C$^{18}$O isotopomer 21SnStBo.