Planetary surfaces are important archives of the origin and evolutionary history of planetary bodies, preserving evidence of a broad range of geological, atmospheric, chemical, and physical processes. Across the Solar System, these processes often operate under extreme conditions, including very high or low temperatures and pressures, intense radiation, large thermal variations, and physico-chemical environments markedly different from those on Earth.

Understanding how planetary materials respond to such conditions, and how these responses modify their observable properties is essential for interpreting remote sensing observations and reconstructing the history and evolution of planetary surfaces.

This focus session explores how extreme environmental conditions such as temperature, pressure, radiation, and chemistry affect the composition, mineralogy, physical properties, and optical characteristics of planetary materials.

Contributions are welcome on topics including:

• Alteration processes, mineralogical changes, and associated variations in the optical and spectroscopic properties of planetary materials under extreme conditions of temperature, pressure, radiation, and chemical environment.
• Effects of solar and cosmic radiation, solar wind, and micrometeoroid bombardment on surface materials.
• Behavior and stability of minerals, rocks, ices, and amorphous materials under extreme extraterrestrial conditions.
• Laboratory experiments and planetary analogues aimed at reproducing and characterizing the effects of extreme temperatures and pressures, irradiation, vacuum, plasma environments, and chemical environments.
• Numerical models and theoretical approaches aimed at understanding the behavior and evolution of materials under extreme conditions.