A Geologic Map of Aram Chaos: A Community Resource to Facilitate Future Scientific Investigations on Mars

Goals and Objectives: We propose to produce a standardized United States Geological Survey (USGS) Scientific Investigation Map (SIM) series geologic map of four Mars Transverse Mercator (MTM) quadrangles at a scale of 1:1,000,000 that covers Aram Chaos (05022, 05017, -00022, and -00017) (-2.5 to 7.5°N latitude, 335 to 345°E longitude). The map will link existing USGS map coverage to the south and east, thereby enabling researchers to understand the role of water, either on the surface or in the subsurface, that formed the chaos terrain, channel and valley development, and origin of sulfate- and hematite-bearing units in an area on Mars where they are preserved at a local and regional scale. The proposed map will also encompass the initial and medial portions of the Ares Vallis channel from the chaotic terrain at Aram Chaos, Iani Chaos, and Hydaspis Chaos. Consequently, the proposed map will provide continuity to the north along the path of the Uzboi-Ladon-Morava (ULM) meso-scale outflow system that extends from Argyre basin to the northern plains, providing a regional scale framework in which to interpret previous mapping to the south that extends from Uzboi to Morava Valles. Previous studies have shown that sulfate-bearing sediments occur within Aram Chaos (which also has crystalline hematite) and Iani Chaos. The timing of water filling Aram crater, collapse in the subsurface to form the chaotic terrains at Aram and Iani Chaos, deposition of the sulfates and crystalline hematite, and water flow to the north as part of Ares Vallis would establish the geologic history for this region and have implications for how the sulfate-bearing sediments formed here in comparison to those in the east (Valles Marineris) and the west (Meridiani Planum), and possibly Gale crater where the Curiosity rover is currently exploring the sulfate-bearing sediments.

Approach and Methodology: Standard planetary mapping principles will be used to define map units based on topography, morphology, stratigraphic relationships, and relative age. Mapping will employ methods and formats consistent with current established guidelines and USGS protocols, and will draw upon the results from prior mapping at similar and smaller scales to ensure consistent definition of units and seamless transitions between existing map coverage. Datasets (e.g., THEMIS, MOLA, CTX, HiRISE, CRISM) will be compiled and analyzed in ArcGIS 10.7 or ArcGIS Pro 2.3, and units and features will be identified using standard USGS symbols. Relative dating of surfaces will employ crater statistics and stratigraphic relationships, where crater statistics will
be compiled in ArcGIS using a subset of a global CTX mosaic and CraterTools, a plug-in software for ArcGIS. Interpreted absolute ages will be derived from segments of the plots for each unit that best match the expected production population based on multiple chronology functions in Craterstats2 software. The resulting map will be comprised of the geologic map text and map package that accompanies USGS standardized maps following the standards established by the USGS Planetary Mapping Group.