BASALT DUST PRODUCED FROM EXPERIMENTAL AEOLIAN SALTATION AND IMPLICATIONS FOR MARTIAN CLIMATE

Aeolian processes have likely been a dominant force for much of Mars’s history. Today, large quantities of dust are transported across Mars by aeolian systems. Processes that generated dust seen now may include volcanism, bolide impacts, glacial grinding, aeolian saltation, and fluvial comminution. Each process might make dust characterized by unique and distinctive particle size distributions. Particle size distribution (PSD) plays a significant role in dust emissivity, transport, and how dust influences climate via both direct radiative forcing and its impact on a potential biosphere through nutrient delivery and reactivity.

Modes of dust generation on Mars may have evolved through time e.g., fluvial comminution and glacial grinding are not active today, but might have played roles in dust generation in the past. If PSDs differ among various dust-generating processes, these processes could exert different influences on climate at different periods in the past. An empirical approach to isolate dust from end-member processes for particle-size analysis is difficult because dust is susceptible to chemical weathering and mixing into soils. Laboratory experiments replicating natural processes are useful in creating these unaltered and unmixed samples for study. Few experiments have attempted to replicate aeolian saltation as a dust-generation mechanism and fewer have attempted to use basalt sand as a Martian analog.

In our experiments we abrade basalt sand from Iceland and Hawaii in a novel device, replicating intergranular collisions experienced during windstorms. Our abrasion device is a small circular wind chamber that accelerates saltating grains in excess of 20 m/s and collides them with a pile of sand, replicating collisions of saltating sand in aeolian dune fields. Prior to abrasion, samples are preprocessed to remove dust-sized grains. Control samples are used to ensure dust analyzed is generated by the experiments. Samples are abraded for four days, wet sieved to remove new dust grains, and assessed using a Laser Particle Size Analyzer.

We present preliminary results of these experiments and discuss possible impacts on climate through radiative forcing. We discuss implications of using dust deposits as proxies for past environments and climates that produce dust based on PSDs.