Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars

Abstract

Images from the Mars Express HRSC (High-Resolution Stereo Camera) of debris aprons at the base of massifs in eastern Hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely ice-rich glacier-like viscous flow and sublimation. Together with new evidence for recent ice-rich rock glaciers at the base of the Olympus Mons scarp superposed on larger Late Amazonian debris-covered piedmont glaciers, we interpret these deposits as evidence for geologically recent and recurring glacial activity in tropical and mid-latitude regions of Mars during periods of increased spin-axis obliquity when polar ice was mobilized and redeposited in microenvironments at lower latitudes. The data indicate that abundant residual ice probably remains in these deposits and that these records of geologically recent climate changes are accessible to future automated and human surface exploration.

Radar evidence for ice in lobate debris aprons in the mid‐northern latitudes of Mars

“…The paucity of craters on the LDAs indicates either formation or substantial deformation in mid-to-late Amazonian time [Chuang and Crown, 2009]. LDAs and the associated lineated valley fill have been interpreted as remnants of much larger cold-based glaciers that have been protected from sublimation by a layer of debris shed from neighboring scarps [Head et al, 2005[Head et al, , 2006a[Head et al, , 2006bMarchant and Head, 2007]. Our observations are consistent with this hypothesis; the surficial layer of lithic material in this scenario comprises only a small volumetric fraction of the LDAs, with minimal effects on the electrical properties.…”

“…Head and Marchant [2006] and Head et al [2006aHead et al [ , 2006b, analyzed lobate and linear debris aprons (and related lineated valley fill) in the Deuteronilus region and interpreted them as debris-covered remnants of glaciers that formed during the Late Amazonian. Image data show many features indicative of flow and surficial modification likely related to the presence of subsurface ice in the LDAs of this region and in LDAs elsewhere on Mars [e.g., Carr and Schaber, 1977;Squyres, 1978Squyres, , 1979Mangold and Allemand, 2001;Mangold, 2003;Pierce and Crown, 2003;Chuang and Crown, 2005;Head et al, 2005Head et al, , 2006aHead et al, , 2006bChuang and Crown, 2009]. In summary, a range of approaches and analyses suggests that ice is important in the formation of the distinctive shapes, profiles, and textures of LDAs, but the exact amount of ice and its mode of emplacement have been controversial.…”

“…Their geomorphic expression and restricted occurrence in latitude has led numerous workers to conclude that LDAs contain water ice, but the suggested amount of ice involved in their formation and evolution has ranged from minor interstitial ice in rocky talus [e.g., Squyres, 1978] to predominantly ice in debris-covered glaciers [e.g., Head et al, 2005; see also Carr and Schaber, 1977;Squyres, 1979;Lucchitta, 1984;Colaprete and Jakosky, 1998;Carr, 2001]. We present new evidence from the Shallow Radar (SHARAD) sounding experiment on Mars Reconnaissance Orbiter (MRO) [Seu et al, 2007] that LDAs in the Deuteronilus Mensae region of the mid-northern latitudes consist mostly of ice.…”

“…Analysis of topographic profiles of LDAs showed them to be consistent with viscous deformation of an ice-rock mixture [Colaprete and Jakosky, 1998;Mangold and Allemand, 2001;Li et al, 2005] but the percentage of ice required to cause flow, and the amount remaining today are uncertain. Ice-assisted creep of talus [Squyres, 1978[Squyres, , 1979 implies less than $20-30% interstitial and secondary ice, while debris-covered glaciers could be >80% ice covered by a thin debris lag [Colaprete and Jakosky, 1998;Head et al, 2005Head et al, , 2006aHead et al, , 2006b, and rock-glacier-like deposits imply intermediate values (30 -80%) [Mangold et al, 2002]. Head and Marchant [2006] and Head et al [2006aHead et al [ , 2006b, analyzed lobate and linear debris aprons (and related lineated valley fill) in the Deuteronilus region and interpreted them as debris-covered remnants of glaciers that formed during the Late Amazonian.…”

Radar Albedo Feature

“…However, these signatures might come from "classical" glaciers as opposed to debris-covered glaciers or rock glaciers (of model (2)). Together with the moraines of glaciers, these might be present at the base of the Olympus Mons scarp (Head et al 2005) and at the northwestern flank of Arsia Mons volcano Fig. 10).…”