Harrison Nicholls (he/him): Publications

Probing Exoplanetary Chemistry with Ariel: Scientific Priorities and Observational Strategies

ArXiv 2609.27622 (2026)

Authors:

Olivia Venot, Yamila Miguel, Robin Baeyens, Stefano Bellotti, Giuseppe Cassone, Quentin Changeat, Ryan Cloutier, Athena Coustenis, Dwaipayan Dubey, Billy Edwards, Kaustubh Hakim, Eric Hébrard, Christiane Helling, Helgi Rafn Hrodmarsson, Leoni Janssen, Adam Yassin Jaziri, Gaia Lacedelli, Panayotis Lavvas, Jorge Lillo-Box, Amy Louca, Adrien Masson, Zita Martins, Karan Molaverdikhani, Benjamín Montesinos, Harrison Nicholls, Enric Palle, Paul Rimmer, Donna Rodgers-Lee, Jonathan Tennyson, Shang-Min Tsai, Roméo Veillet, Sergey N Yurchenko, Maria Zamyatina

Super-Earth Interiors Shrink by About 10% as They Crystallise

ArXiv 2609.23091 (2026)

Authors:

Tim Lichtenberg, Mara Attia, Harrison Nicholls, Mariana Sastre, Dan J Bower, Karen Stuitje, Flavia C Pascal, Laurent Soucasse, Daniel Apai, Patrick Bos, Robb Calder, Lorenzo Cesario, Lisa Dang, Emeline Decocq, Marijn van Dijk, Mohammad Farhat, Kaustubh Hakim, Tadahiro Kimura, Imre Kisvárdai, Sebastiaan Krijt, Yamila Miguel, Ioannis Panagiotou, Emma Postolec, Martin Schlecker, Sara Seager, Anat Shahar, Oliver Shorttle, Paolo A Sossi, Wim van Westrenen

Evolutionary pathways toward survival of a thick CO2- or SO2-rich atmosphere on the lava world TOI-561 b

ArXiv 2609.03144 (2026)

Authors:

Emma Postolec, Tim Lichtenberg, Johanna K Teske, Harrison Nicholls, Mara Attia, Anjali Piette, Lisa Dang, Nicole L Wallack, Mykhaylo Plotnykov, Alex McGinty, Samuel Boucher, Bo Peng, Diana Valencia

Geophysical and atmospheric implications of f O ₂ -dependent melting on rocky exoplanets

Astronomy & Astrophysics EDP Sciences 713 (2026) A159-A159

Authors:

Mariana Sastre, Tim Lichtenberg, Laurent Soucasse, Dan J Bower, Harrison Nicholls, Inga Kamp

Abstract:

The geochemical evolution of long-lived magma oceans is strongly regulated by the volatile exchange between the molten mantle and the atmosphere. For planets inside the runaway-greenhouse limit, this coupled evolution can persist for billions of years, governing bulk density, surface conditions, and long-term geodynamics. However, most existing studies assume Earth-like (oxidized) conditions and neglect the influence of the redox state on melt thermodynamics and volatile release. We quantified how experimentally derived, oxygen-fugacity-dependent melting curves implemented within the coupled interior-atmosphere framework PROTEUS propagate into the thermal structure, melt fraction, and rheological evolution of rocky exoplanet interiors, and applied this to the short-period super-Earth GJ 1132 b. We found strongly non-linear thermal responses to variations in melting curves. In volatile-poor systems, reduced melting curves ( f O 2 ≤ IW, where IW denotes the iron–wüstite buffer) promote earlier deep-mantle crystallization relative to oxidized (IW+2.0) and Earth-like (IW + 4.0) cases (range IW–4.0 to IW + 4.0), favouring late-stage surface magma oceans sustained by greenhouse warming, while oxidized melting curves maintain higher melt fractions and a vertically extended magma ocean. Reduced mantles produce massive H 2 –CO-rich atmospheres; oxidized mantles favour thinner H 2 ��–C�� 2 envelopes. In volatile-rich systems, the interior reaches radiative equilibrium at high melt fractions, sustaining a steady-state global magma ocean in which melting curve variations do not significantly influence solidification timing. This indicates a hierarchical control: volatile inventory and surface oxygen fugacity act as the primary regulators of thermal state, while oxygen-fugacity-dependent melting relations provide a secondary modulation. These contrasting regimes produce distinct atmospheric compositions and formation timescales, offering testable spectral predictions for close-in rocky exoplanets evaluable with forthcoming JWST observations.

A Highly Reflective Atmosphere on the Lava World TOI-561b Revealed by JWST/NIRSpec Phase Curve

ArXiv 2608.21519 (2026)

Authors:

Samuel Boucher, Lisa Dang, Alex McGinty, Johanna K Teske, Raymond Pierrehumbert, Anjali AA Piette, Nicole L Wallack, Angharad Weeks, Neil T Lewis, Tim Lichtenberg, Mykhaylo Plotnykov, Emma Postolec, Daniel Huber, Timothy R Bedding, Harrison Nicholls, Bo Peng, Mark Hammond, Diana Valencia

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