THE EFFECT OF COMPOSITION VARIATION ON MANTLE SOLIDUS AND THERMAL EVOLUTION OF ROCKY PLANETS

Understanding exoplanet interiors remains a challenge in the planetary science community due to the difficulty of direct observation. While atmospheres of these planets are being observed using advanced telescopes like HST and JWST, interior modeling provides information about their interior structure, composition, and evolution. They describe the processes within a planet’s deep interior, such as heat transport and magnetic field generation, as well as surface processes like outgassing and volcanism. It helps us to understand the formation of secondary atmospheres and the habitable architecture of the planet. Current models often assume an Earth-like interior mineral composition, which oversimplifies the complexity of exoplanetary mantles. The preliminary composition of the planet often resembles the composition of refractory materials present in the host star, since they form from the same primordial gas clouds.

Our research investigates how variations in interior composition affect the solidus and, consequently, the planet’s thermal history. On Earth, olivine and pyroxene are key ultramafic minerals in the mantle. Variability in elemental abundances in stars suggests planets may have diverse olivine-pyroxene ratios. By studying these changes, we aim to understand how different mineralogies affect the mantle's solidus profile using the MELTS software. The solidus, marking the onset of melting, is crucial for determining cooling rates and melt production. We integrate it with the mantle adiabat and heat sources/sinks to simulate interactions between mantle composition, temperature, pressure, viscosity, and lid growth over geological timescales. This helps us understand heat transport, melt production, volatile outgassing, volcanism, and other dynamic processes during a rocky planet’s evolution, aiding in predicting the thermal and geological history of exoplanets. Understanding these processes is essential for identifying planets that may support life, as the presence of tectonic activity and volcanism can create and sustain habitable conditions over long periods.