Investigating Volatile-Related Processes on Rocky Planetary Bodies

• Applicant: Dr. Tanja Michalik
• Subject Area: Palaeontology ; Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography ; Mineralogy, Petrology and Geochemistry
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 528399203

In this interdisciplinary project in the area of planetary science, I try to understand how endogenic mafic material on differentiated planetary surfaces interacts with exogenic volatile-bearing material. In doing so, the disciplines general geology, remote sensing and mineralogy/geochemistry are combined. This project focusses on the question whether mineralogical changes can occur within mafic minerals during a devolatilization event, and what kind of influence this might have on the reflectance spectra of planetary surfaces. The mineralogical changes could be provoked by an oxidation process, which may occur as the result of previously bound volatiles being released during an impact event. In the course of this project, I will transmit the results of already existing observations and laboratory experiments regarding the asteroid (4) Vesta to Mars and the Moon as well as conduct continuative mineralogical analysis. Vesta possesses numerous ejecta deposits that exhibit morphologies indicating a devolatilization process. These morphologies show distinct spectral properties, whereas the causes are still uncertain. The pyroxene-dominated reflectance spectra of the surfaces of these devolatilization morphologies are characterized by higher overall reflectances, more pronounced mafic absorption bands and lower OH abundances with respect to the adjacent material of the same ejecta deposit. A current hypothesis suggests changes in the occupation of the M1 and M2 sites within the pyroxene crystals or the migration of iron cations within the crystal as the cause of the different spectral properties. By means of Mössbauer spectroscopy and electron microprobe analysis, I will test this hypothesis on already existing analog samples. Moreover, this project aims at increasing the number of planetary objects being investigated. Widespread devolatilization morphologies on Mars are geologically and morphologically very similar to those on Vesta, yet have not been spectrally characterized nor spectrally compared to the Vestan morphologies. Such study could draw a more comprehensive picture of these morphologies and possibly help elucidate the causes for the spectral distinctness on Vesta. In addition, I will reconsider the so-called lunar swirls in the light of the abovementioned hypothesis. The lunar swirls exhibit very similar spectral properties as the devolatilization morphologies on Vesta, yet they have not been scientifically connected. The currently most acknowledged theory involves local magnetic fields that partly shield the area of lunar swirls from the solar wind. With selective spectral analyses, I intend to clarify whether an interaction with volatiles might also be able to cause these phenomena.

• DFG Programme: WBP Position