Structure and Origin of the Martian Latitude Dependent Mantle Revealed by Ice-Exposing Scarps

Kurzfassung

Assessing the nature and distribution of water ice in the mid-latitudes of Mars is fundamental for the understanding of the planet’s recent climate history [1], and for characterizing ice reservoirs as a resource for future sustainable human exploration [2]. Martian mid-to-high latitudes are covered by a young smooth deposit that drapes the topography: the “latitude dependent mantle” (LDM) [3, 4, 5]. Almost continuous above 55° latitude, it becomes thinner, degraded and discontinuous towards lower latitudes, disappearing around 30°. Numerous observations [2 and references therein] indicate that the LDM contains at least 46% of water ice by volume [6]. While this ice is usually covered by a layer of dry regolith several centimeters thick, instances of exposure occur on back- wasted scarp faces, allowing the ice and internal structure of the mantle to be explored [7, 8, 9]. These ice exposing scarps (IES) are located at the head of triangular depressions and face directly towards the poles, as shown in Fig. 1. They expose a stratified, relatively bluish-colored material visible year-round in HiRISE and CaSSIS color images, which CRISM observations have confirmed to be water ice with < 1% contamination [7]. Recent models suggest that IES are actively retreating at a rate of a few mm per year [10]. In this work, we build on the efforts of [7, 8] by completing the mapping of IES across the entire planet and studying in detail their morphology, context, and the characteristics of the exposed ice. This analysis aims to shed light on the origin of the LDM, its internal structure, and the global distribution and internal stratification of near-surface ice deposits in Martian mid-latitudes.