Generation of Martian chaos and channels by debris flows

Abstract

A debris flow mechanism is proposed to account for the formation of chaos and the large channels debouching into Chryse Planitia from the adjacent southern uplands of Mars. The debris is thought to have originated through a mechanism of collapse in the chaotic terrains which exist at the head of these channels as well as locally along the channels. This proposition is based on the detailed morphologic similarities between Martian channel source areas and the heads of both subaerial and subaqueous terrestrial debris flows. The downslope movement of the debris produced the channels through (a) modification of earlier collapse areas, (b) active bed erosion, and (c) loading-induced collapse. The large-scale channel geometry and the assemblage of related morphologic features on Mars correspond tto that observed in subaqueous debris flow chutes on the Mississippi delta front. Through various mechanisms of strain-dependent viscosity decrease the debris flow gained mobility downstream, turned into a debris avalanche, and moved onto Chryse Planitia at very high velocities. This high-velocity avalanche eroded a series of streamlined remnants near the channel mouths and deposited its load as a thin blanket over a large area of the basin creating virtually no depositional relief.