142-2 Geologic Map of the Aram Chaos Region: New Insights into Water Flow and Chaos Formation

Session: Geomorphology and Landscape Evolution of Mars (Posters)

Poster Booth No.: 324

Presenting Author:

Catherine Weitz

Authors:

Weitz, Catherine¹, Wilson Purdy, Sharon A.², Grant, John A.³

(1) Planetary Science Institute, Arlington, VA, USA, (2) Smithsonian Institution, Washington, DC, , (3) Smithsonian Institution, Washington, DC, USA,

Abstract:

We are producing a standardized USGS Scientific Investigation Map (SIM) series geologic map of Mars Transverse Mercator (MTM) quadrangles 05022, 05017, -00022, and -00017 that encompasses the initial and medial portions of the Ares Vallis channel from the chaotic terrain at Aram Chaos, Iani Chaos, and Hydaspis Chaos (-2.5 to 7.5°N latitude, 335 to 345°E longitude). All mapping is being done at 1:1,000,000 (1:1M) in ArcPro using a CTX mosaic as the basemap, supplemented with THEMIS Daytime and Nighttime IR mosaics, HRSC-MOLA DEM topography, HiRISE images, and CRISM spectral parameters. We have defined 32 geologic units in our map and have divided them into 6 groups: Chaos Units, Highland Units, Crater Units, Channel Units, Landslide Unit, Sedimentary Units. Surface features include secondary crater chains and linear features include depression margins, wrinkle ridges, troughs, grabens, crater rims, and channels.

All surface flow can be mapped back to chaos terrain in the south, supporting the idea that formation of the chaos terrain resulted in the release of surface water that modified and eroded much of the map region. Sedimentary deposits composed of smooth fill occur throughout much of the highlands, indicating periods of both erosion and deposition as the flow changed in velocity and strength. The ferric hydroxysulfate found within Aram Chaos can only form by heating hydrated ferrous sulfates above 100°C and it is associated with upturned and tilted chaos blocks, implying a heating event within the subsurface relatively recently in martian history (<3 billion years ago). Potential geothermal heating could have arisen from intrusion of magma near the surface that would have melted and released large quantities of water stored in the subsurface, leading to formation of the chaos and surface water flow. A summarized geologic history includes: (1) Formation of the impact basin which now encompasses Aram Chaos; (2) Collection of water in the subsurface from the Uzboi-Morava-Ladon outflow channel system; (3) Magmatic heating in the subsurface that released water across a broad area and formed the chaos; (4) Confinement of water into major channels (Ares and Jhelum Vallis); (5) Deposition of sulfates within Aram and Iani chaos; (6) Continued heating in the subsurface to alter some monohydrated sulfates to ferric hydroxysulfate, and also uplift and tilting of pre-existing chaos blocks within Aram.

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