Environmental records in windblown sand dunes across the Solar System

Windblown dunes are common features in our solar system, forming on planetary surfaces that span wide ranges in gravity and both atmospheric and sediment properties. These features record time-integrated interactions between a planet’s atmosphere and surface. First, I show how the patterns formed by dune crestlines record information about recent (<104 yr.)changes in environmental conditions (e.g., shifts in wind regime or varying sediment availability). When paired with an elementary approach to quantify dune migration, these results suggest that the adjustment time of large dunes is often longer than the timescale of climate cyclicity. Furthermore, this work offers a novel tool to detect and possibly quantify recent environmental change on planetary surfaces. The near-equatorial belt of dunes on Saturn’s moon Titan provides an ideal application of this framework. A dune pattern analysis reveals that dunes on Titan are interconnected and form the largest known dune field in the Solar System and lend critical insights into the material nature of sand grains themselves.

Next, the ubiquity of windblown features across planetary surface is nontrivial because of the specific conditions necessary for dune formation: wind speeds must be just right for grains to ballistically hop (“saltate”) across the surface. To understand how this happens, I combined global wind reanalysis with grain size measurements and dune simulations to show that dune fields on Earth are characterized by a near-transport threshold state where dune-forming winds minimally exceed the saltation threshold. Importantly, these results show that wind speeds can be precisely estimated from aeolian sandstones and dune deposits across planets. Finally, we utilize wind and grain size measurements from the Curiosity rover to show that dunes at Gale crater on Mars are dynamically similar to their counterparts on Earth. Altogether, dunes and their constitutive grains provide a robust record of their formative conditions, opening new lines of investigation for paleo-environmental reconstructions on Earth and beyond.