EP041-10
Conditions for aeolian transport in the Solar System
Conditions for aeolian transport in the Solar System
Friday, 11 December 2020: 07:27
Virtual
Abstract:
Dunes are found across the Solar System. They arise and evolve because loose sediment is moved by goldilocks winds: those that are fast enough to move grains, but not too fast to suspend grains. The mere presence of dunes on a surface therefore tells us something about that planetary body, and perhaps surprises us where the environments are so alien; take Pluto’s thin atmosphere for example.
Mars also presents a conundrum: current climate models indicate winds rarely exceed threshold, yet repeat observations show active dune and ripple migration. Current approaches for predicting the threshold of wind-blown transport lose meaning and diverge from one another when extrapolated to exotic bodies and the wind-tunnel experiments that mimic them. This is because no theory includes all the relevant physics for every planetary body in our Solar System. Here we draw on results in contact, rarefied gas, statistical and adhesion mechanics to present more complete theories for the ‘fluid’ and ‘impact’ thresholds of aeolian transport. This novel analysis, that resolves the entire force balance on particles and their trajectories, compares well with the largest compilation of threshold observations to date. Applying these results, we shed light on the contentious issues of sediment mineralogy on Titan, and the high threshold for dune activity on Mars. This work provides reliable predictions for unexplored bodies, and reveals what observations are required for progress on this topic.
Mars also presents a conundrum: current climate models indicate winds rarely exceed threshold, yet repeat observations show active dune and ripple migration. Current approaches for predicting the threshold of wind-blown transport lose meaning and diverge from one another when extrapolated to exotic bodies and the wind-tunnel experiments that mimic them. This is because no theory includes all the relevant physics for every planetary body in our Solar System. Here we draw on results in contact, rarefied gas, statistical and adhesion mechanics to present more complete theories for the ‘fluid’ and ‘impact’ thresholds of aeolian transport. This novel analysis, that resolves the entire force balance on particles and their trajectories, compares well with the largest compilation of threshold observations to date. Applying these results, we shed light on the contentious issues of sediment mineralogy on Titan, and the high threshold for dune activity on Mars. This work provides reliable predictions for unexplored bodies, and reveals what observations are required for progress on this topic.