MALEA PLANUM'S SONG OF ICE AND FIRE: LARGE-SCALE, PROTRACTED DEPOSITION AND EROSION ON MARS' OLDEST VOLCANIC PROVINCE

Late Noachian to early Hesperian-aged Malea Planum has been suggested as the site of large-scale volcano-ice interactions and as a major source for deposits now filling the adjacent Hellas basin to the north. Activity on Malea Planum might also have affected the south polar Dorsa Argentea Formation immediately to the south, which has repeatedly been interpreted as a product of widespread wet-based glaciation affected by volcanic heat. Furthermore, it has been stated that such large-scale volatile mobilization and potential gas release should have affected the early martian climate and regional habitability. We synthesized our comprehensive investigation of the area into a 1:2,000,000 photogeologic map of the area, which we defined as quadrangle comprising the entirety of the wrinkle ridged plains constituting Malea Planum. Using all state-of-the-art datasets, we identified 26 geomorphologic units assigned to six groups. We compiled the area's chronostratigraphy based on superposition relations, with crater size-frequency-derived apparent model ages (AMAs) of six units as calibration points. Aside from crater ejecta and Amazonian veneers, we identified at least six distinct, major depositional units in our mapping area spanning a time period from ~3.8 Ga to at least 3.5 Ga. While the wrinkle-ridged plains still cover the majority of the region, we suggest that only small percentages of the other five deposits remain. Based on morphometric observations, volumes on the order of 400,000 to 500,000 km³ of these units might have been removed from Malea Planum. Therefore, while Hesperia Planum likely contributed the majority of the once ~10⁶ km³ of Hellas infill, Malea Planum should also have decisively contributed to the basin’s infilling. While large-scale volatile mobilization of up to ~10⁶ km³ via volcanic heating has previously been suggested for Malea Planum, our assessment of the region’s geomorphologic record implies not one catastrophic event, but several distinct episodes of erosion that occurred over several 100s of Ma. Furthermore, some (glacio)-fluvial landforms traverse the entirety of Malea Planum from south to north, therefore implying a ~1,600 km long drainage system that also fed the Hellas basin with sediments and volatiles from today’s South Pole region.