Granular flow processes such as landslides are key contributors to geological hazards in high-altitude terrains and on extraterrestrial planetary surfaces. These environments are characterized by extremely low atmospheric pressures, which significantly alter gas–solid interactions and flow behavior. This study examines the influence of ambient pressure on granular avalanche dynamics using a custom-designed horizontal rotating drum system. Experiments with uniform spherical particles and high-speed imaging were used to quantify characteristic angular parameters, characteristic temporal parameters, velocity fields, and internal flow structures. Results show that reduced pressure lowers both the initiation and deposition angles of avalanches, leading to greater instability of granular assemblies. Low-pressure conditions also prolong the avalanche cycle by increasing the rest time needed for the system to reach instability. Despite reduced air resistance, lower pressure leads to slower particle motion due to decreased initial potential energy. Flow field analysis reveals that high-pressure environments induce greater shear, velocity gradients, and vortex structures. These findings provide new experimental evidence for how ambient pressure modulates granular flow dynamics and offer valuable insights into the formation and evolution of landslides in high-altitude regions and on celestial bodies.

granular flow,landslide,flow characteristics,ambient pressure