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

火星已将大部分初始水以原子氢和氧的形式流失到太空。航天器测量已经确定，当今的氢逃逸随着季节的变化而发生很大的变化，这与长期以来的解释不一致。原因尚不完全清楚，可能是大气环流、尘埃活动和太阳极紫外线输入的季节性变化造成的。尽管一些建模和间接观测证据表明沙尘活动可以解释季节性趋势，但之前的研究无法明确地区分季节性和沙尘驱动的强迫。在这里，我们展示了在区域尘埃事件期间火星上的尘埃、温度、冰、水和氢的天气测量结果，表明单个尘埃事件可以将行星 H 损失增加五到十倍。这场区域风暴发生在已知季节性趋势的下降阶段，表明沙尘强迫可以超越这一趋势，从而推动增强逃逸。因为类似的区域风暴在火星的大部分年份都会发生，这些风暴可能是火星失水的主要原因，并且是火星大气演化的重要驱动力。