Martian water loss to space enhanced by regional dust storms

Mars has lost most of its initial water to space as atomic hydrogen and oxygen. Spacecraft measurements have determined that present-day escape undergoes large variations with season are inconsistent long-standing explanations. The cause is incompletely understood, likely contributions from seasonal changes in atmospheric circulation, dust activity solar extreme ultraviolet input. Although some modelling indirect observational evidence suggest can explain the trend, no previous study been able unambiguously distinguish dust-driven forcing. Here we present synoptic dust, temperature, ice, on during a regional event, demonstrating individual events boost planetary H loss by factor five ten. This storm occurred declining phase known establishing forcing override this trend drive enhanced escape. Because similar storms occur years, these may be responsible for fraction Martian represent an important driver evolution. Multi-spacecraft observations ice opacities, vapour abundances, thermospheric atmosphere local show even such events, much more frequent than global storms,