The Titan Wind Tunnel: A new tool for investigating extraterrestrial aeolian environments

Aeolian processes occur throughout the Solar System and likely on extrasolar planets as well. Models based on data collected in boundary layer wind tunnels have contributed to understanding the physics of these processes. Planetary wind tunnels allow simulation of conditions (atmospheric pressure, density, or kinematic viscosity) on extraterrestrial bodies, and their use over several decades has demonstrated important differences between terrestrial and extraterrestrial aeolian processes. A high-pressure wind tunnel is now available in the Planetary Aeolian Laboratory (PAL) at the NASA Ames Research Center. Used up to the early 1990's for Venus analog experiments, this wind tunnel has been refurbished and is now in use as the Titan Wind Tunnel (TWT) for Titan analog experiments. Initial results for threshold friction wind speeds at Titan analog conditions do not agree with models based on experimental data at terrestrial, Martian, and Venusian analog conditions (Burr et al., 2015). These results from the TWT work continue a history of wind tunnel experiments that show repeated under-prediction of threshold by models based on non-analog conditions. In addition to suggesting caution in extrapolating from one surface environment to another, this historical record highlights the utility of experiments in wind tunnels that provide closely analogous conditions to the environment of interest. The TWT, along with other PAL facilities, provides the means for further analog experiments by the scientific community to support continued advancement in understanding planetary aeolian processes.