Geological History of Southern Gorgonum Chaos, Mars: A Story of Water and Wind

Gorgonum Chaos is part of the Eridania paleolake in Terra Sirenum and displays a number of prominent light-toned morphological features that bear a record of the regional climatic conditions throughout most of Martian history. Based on an integrated analysis of orbital data, we mapped a 1,500 km2 area in the southeast of Gorgonum Chaos. Morphologic, spectroscopic, and stratigraphic analyses were used to determine age and composition of the main geological units in the area. We identified four major geological units with decreasing content of hydrated minerals from the oldest to the youngest units, which were completely free of hydrated minerals. In the study area, phyllosilicate-rich Noachian units compose the majority of the basin floor. Deposits enriched with evaporites were formed around the Noachian/Hesperian transition and erosion created prominent inverted morphologies. Loess-like material without significant amounts of hydrated minerals was deposited until the late Hesperian. The youngest unit is an Amazonian layer free of hydrated minerals that originated from volcanic activities. This succession of minerals reflects the transition from more humid climatic conditions with the ability to sustain liquid water on the planet's surface during the Noachian to the hyper-arid Amazonian environment we observe currently on Mars