Producing Dust through Simulated Glacial Abrasion of Basalt Clasts with Implications for Mars

Abstract

Multiple processes have been proposed for the genesis of dust on Mars, including volcanic eruptions, eolian abrasion, bolide impacts, and glacial grinding. Atmospheric dust has a significant impact on climate that is heavily dependent on the particle size distribution (PSD) of the dust. Therefore, we ask, do different dust-generating mechanisms produce different dust PSDs and, consequently, different impacts on the climate? Glacial grinding is the erosive process of clasts embedded in the base of a glacier sliding across bedrock or subglacial sediment. We use basalt clasts as analogs to assess sediment production via experimental glacial grinding. We cut small (3 cm), flat- and point-tipped fabricated clasts from five distinct basalts and used a novel experimental apparatus to abrade them across a basal rock slab representing bedrock. Pointed clasts generally produced more sediment than flat clasts, as did clasts with vesicular textures compared to those with nonvesicular textures. The resulting PSDs show that most dust samples exhibit a primary mode, between 20 and 50 μm. These results indicate a tendency toward silt production from rock-on-rock grinding of basalt, akin to the conditions at the base of a wet-based glacier. Results were compared to sediment PSDs from other potential dust-producing mechanisms. Simulated glacial grinding of basalt generates proportionally ∼50% more fine dust (<2.5 μm) than simulated eolian abrasion of basalt sand. Results from these experiments suggest that if widespread wet-based glaciation existed on Mars, the dust produced would have influenced the climate, although the net radiative effect is unknown.