Comminution of Aeolian Materials on Mars

Grant #: NNX12AO39G
Senior Scientist: John Marshall



The project will attempt to demonstrate experimentally that aeolian action on Mars leads to the production of vast quantities of silt that have an anomalous mixture of extremely well-rounded grains and extremely angular material. Because of the physics governing particle comminution, this silt population, generally neglected in Mars geology, may be the predominant sediment on Mars, concealed by its low-profile expression; no obvious dune formation as for sand, and no obvious atmospheric entrainment as for dust. Methods: A unique centrifuge comminution apparatus will be employed to simulate the aeolian processing of grains. The apparatus simulates an aeolian transport environment in which grains impact other grains with highly controlled impact velocities, angles, and flux. The apparatus retains all attrition products for later examination. Both the comminuted grains (source of rounded material) and their attrition products (source of angular material) are of interest. Electrostatic grain behavior is also recorded and can be regulated. SEM and size analysis investigations of grains and their attrition products will be systematically conducted. Significance: Results have implications for the evolution of the martian soil which has accumulated the silt comminution products of eons. If the soil is as rich in silt as predicted, it has significant implications for soil strength, induration, and chemical reactivity, as well as permeability for volatiles that are a key factor in mediating atmospheric-regolithic interactions relating to the global moisture budget. Grain-size distribution in soils also determines if a region yields to the development of dune fields (sand-controlled), storms (dust-controlled), or relatively inactive and indistinct plains of loessic (silt) material. Results of the research will assist interpretation of the Phoenix mission soil microscopy data.