Distal Flow Deposits: Exploring Impact Related Surface Flow Morphologies Beyond the Layered Ejecta Blankets of Mars
Abstract
Over the past 20 years, several studies have indicated that continuous emplacement on Mars may often be significantly more geographically extensive than current models suggest. Around just a few source craters, surface flow morphologies beyond the layered and often rugged-textured continuous ejecta blanket have been reported and have been suggested to result from an extended continuous ejecta unit. Despite the recent identification of such deposits, it is currently uncertain how such deposits form, and under what conditions. With the goal of answering such questions, we have carried out a survey of Mars that identifies and helps characterize additional craters where extensive fluid-like surface flow deposits distal to the proximal ejecta layers can be observed. Through this analysis and the comprehensive characterization of all identified deposits, we aimed to understand the conditions necessary for the development of these distal surface flow morphologies, which are henceforth referred to as Distal Flow Deposits (DFDs). Through the identification of 41 DFD-bearing crater candidates between 3.1 and 150 km in diameter (21 high confidence and 20 awaiting HiRISE verification images), DFDs are shown to exist around well-preserved craters throughout the mid-latitude and equatorial regions of Mars (35.7ºS to 25.11ºN). Geomorphological and morphometric analysis suggests DFDs form as an extended continuous ejecta unit travels outwards from the source crater via ground flow. DFDs accumulate where existing target topography captures more extended ejecta than surrounding flat-lying terrains that are resurfaced or obscured by the same deposits.