mardi 13 février 2024, par Mireia LEON-DASI (LESIA)
Lundi 19 fĂ©vrier 2024 à 16h00 , Lieu : Salle de confĂ©rence du bâtiment 17
Volcanism plays a major role in Mercury’s geological processes, and understanding this activity is crucial to delimit the evolution of the planet. The presence of large pyroclastic deposits contrasts with formation models which predict a volatile depleted crust and mantle, especially in the recent past. Constraining the timing of these volcanic eruptions and the extent of the resulting pyroclastic deposits is fundamental to refine our knowledge of Mercury’s internal evolution and improve the formation models. Using a Deep Learning approach with MESSENGER/MASCS spectra we delimit the extent of irregular pyroclastic deposits and update the area of these features. Moreover, we study the evolution of the spectral properties of pyroclastic deposits over time, using the degradation state of the vent as a reference for the deposit age. We observe a trend between the deposit spectra and the vent degradation characterized by a rapid initial darkening and flattening over time followed by stabilization. The oldest deposits reach a steady state with no further spectral changes. To explain these temporal variations in spectral properties, we propose three potential processes : space weathering, mixing with the background and changes in pyroclast size over time. We examine the implications of space weathering on spectral properties and discuss the eruption timeline for each scenario. Finally, we introduce the ongoing lab measurement campaign to study the effect of grain size and composition on the spectral properties of Mercury analogs, with the aim of improving our knowledge of how different processes can affect the spectra of this planet.
