DIX Planetary Science Seminar
As Earth's climate changes, our need to understand the complex processes controlling climate and Earth's biogeochemical cycles increases. Major Earth systems models consider the role of atmospheric mineral dust, which is known to have a net radiative forcing effect in the atmosphere, influence cloud formation, and alter ocean biogeochemistry, among other roles. However, the nature and extent of mineral dust aerosols' impacts on climate cycles depends on its mineralogy and grain size and is currently unclear, including whether dust has a warming or cooling effect and how it influences cloud formation. The Earth Surface Mineral Dust Source Investigation (EMIT) is collecting visible/near infrared (VNIR) spectral data of dust source region land areas to inform how emitted dust mineralogy affects the climate system. Here, we examine the spectral variability of desert dust source regions as observed by EMIT. We developed a method for sampling available EMIT data to build a dataset representative of Earth's arid dust source regions. We use the observations to assess dust source diversity with respect to composition and properties important to biogeochemical processes.
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The dwarf planet Ceres is a main belt outlier in terms of its large size (⌀ ~ 950 km) and spectral properties. Its surface is dotted with domes, mounds, bright carbonate salts, and ice deposits, which point to the density-driven exchange with the subsurface. Specific mechanisms of such an exchange remain an open question. We approach this question by studying the surface ice deposits. The NASA Dawn mission that orbited Ceres between 2015 and 2018 made multiple spectroscopic observations of ice outside its thermal stability region. These raised questions about the nature of ice. Was it excavated by impacts, or does it require recent emplacement? Does it have any links to the exposures of bright sodium carbonates ("salts" here)? These questions motivated our work. Using the Dawn Visible and Infrared spectrometer and Framing Camera images, we mapped ice in a spatially resolved manner at confirmed locations and studied its geological context. We investigated ice grain size, abundance, and mixing mode with regolith using Hapke spectral models. Finally, we mapped salt at locations with ice detections to assess the spatial relationships between them. We use observations to propose a conceptual model for the evolution of Ceres' ice exposures.