Concentric crater fill: Rates of glacial accumulation, infilling and deglaciation in the amazonian and noachian of mars

September 10, 2014 News and Events, Publications

J. L. Fastook and J. W. Head. Concentric crater fill: Rates of glacial accumulation, infilling and deglaciation in the amazonian and noachian of mars. Lunar and Planetary Science XXXXV, #1227, 2014.

Introduction:
Concentric Crater Fill (CCF) [1-6] is one of many features on Mars that are thought to either contain ice, or to have been formed by a glaciological process that involved the deformation and movement of a significant thickness of ice, emplaced during a climatic period when the obliquity and other spin-orbital parameters favored deposition in areas where ice is not currently stable [7-10]. Such features include Tropical Mountain Glaciers [11-15], Lobate Debris Aprons, and Lineated Valley Fill [12, 16-28]. Others, such as Pedestal, Perched, and Excess Ejecta Craters [29-32], record the presence of widespread mantling. Features that preserve ice presumably do so by covering the ice surface with a thin (< 15 m) layer of debris [33-37]. In all cases, understanding the mechanism that leads to the formation of these features provides insights into the state of the current climate and how it must have changed in the past.

Although there are many hypotheses of how CCF might have formed (see [1,3] for a comprehensive discussion), in this we assume that CCF is composed largely of debris-covered ice that at some point flowed and then sublimated, producing the observed flow-like debris cover (Fig. 1, [3]), and that the age is Amazonian [2,3,5,6]. Pedestal Craters record a repeating, transient, widespread ice mantling, and even provide estimates of the thickness of this layer [30-32]. The question then is how does a thin mantling layer flow in such a way as to fill CCF craters with ice to a depth of more than a km? Could it have happened during a single, presumably most recent, episode of mantling,? Or, is it a cumulative gathering of material into the crater during frequent repeated episodes of mantling?