Dresden 2026 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 32: Focus Session: Water – from Atmosphere to Space IV (joint session CPP/DY)

CPP 32.2: Talk

Wednesday, March 11, 2026, 10:00–10:15, ZEU/0260

Water in exoplanetary atmospheres: from molecular spectra to Water Worlds — •Sergey Yurchenko — Department of Physics and Astronomy, University College London, Gower Street, WC1E 6BT London, United Kingdom

Water vapour is one of the key tracers of atmospheric physics and chemistry on exoplanets, from hot Jupiters to temperate sub-Neptunes and so-called Water Worlds. In this contribution I will give an overview of the role of H₂O across this diversity of atmospheres, focusing on how we infer its presence from transmission and emission spectra. I will review both low-resolution transit spectroscopy and high-resolution cross-correlation techniques, and show how they are applied to data from space- and ground-based facilities, including JWST, Hubble and VLT, as well as future observations with the ELT and ESA’s Ariel mission. Special emphasis will be placed on the way clouds and hazes imprint themselves on the observed spectra.

I will summarise the current observational status of water detections and non-detections – including recent and sometimes controversial claims for habitable-zone planets. A central theme of the talk will be the importance of accurate laboratory and theoretical data for water and related species. I will highlight how comprehensive molecular line lists and cross sections from the ExoMol and HITRAN databases, together with other laboratory measurements, underpin the modelling and retrieval of exoplanet spectra over a wide range of temperatures, pressures and compositions, thereby linking detailed molecular physics to the emerging picture of water in exoplanetary atmospheres.

Keywords: Exoplanets; Spectroscopy; ExoMol; Atmosphere; JWST