PROGRESS ON CREATING A 1:60 K GEOLOGIC MAP OF WESTERN AEOLIA MONS, MARS

The focus of this geologic mapping effort is to better understand the stratigraphy and mode of formation of unconformable units on Aeolis Mons, informally known as Mt. Sharp. We have achieved progress in three different areas as described below.

HiRISE image mosaic: Our first task in this project was to supplement the existing CTX basemap with a mosaic of HiRISE images, improving the pixel spacing from 5 m to 0.25 m. We selected 45 images to generate our base layer. These images were individually georectified to the CTX base layer and to each other. Tie points were manually selected, and the images were corrected using a second-order polynomial transformation. The final mosaic is 152 GB in size.

Reconnaissance mapping: While the HiRISE mosaic was being constructed, we pursed two separate ancillary activities. We created the first in a series of interim mapping products – informal maps done quickly to help initially identify major units and delineate contacts. Our objective is to repeat this exercise multiple times by different team members to provide guidance to later, more formal mapping efforts.

Gale sediment balance: A second interim activity was an estimation of the overland transport capacity into Gale crater [1]. Using available topographic data, we compared the mound volume to the volume that could conceivably have been transported by the existing overland transportation network, i.e., the valley network that drains from the southern highlands into Gale crater.

The volume of Mt. Sharp was found to be ~9 ´ 10³ km³, assuming a -4500 m base elevation. The small channels draining from the rim of the crater inward could have contributed about 30 km³ of sediment, while the larger breeching inlet channel (Farah Vallis) could have contributed ~6 ´ 10² km³, including both the channel volume and a conservative estimate of overland, unchannelized flow.

The results of this analysis indicate that the volume of the mound exceeds the carrying capacity of the contributory fluvial network by more than a factor of 10. Thus, mechanisms other than fluvial transport are needed to explain more than 90% of the mound’s sedimentary budget.

References: [1] Thomson B.J. et al. (2015) LPSC 46, abstract #2280.