Seasonal Marsquakes Reveal Shallow Groundwater Activity on Mars

Growing evidence supports the existence of subsurface water ice on Mars, though direct evidence of groundwater remains scarce. Using seismic data from seasonal marsquakes, we provide compelling evidence for groundwater within approximately 2 meters of the surface, restricted to localized regions in the northern mid-latitudes. The observed rapid seasonal variability in seasonal marsquake activity suggests that changes in subsurface pore pressure, driven by water ice melting during warmer seasons, play a critical role in triggering these events. This mechanism explains key characteristics of seasonal marsquakes, including their spatial clustering, elevated b-values, and shallow focal depths. Our findings offer new insights into the present-day water cycle on Mars, shedding light on the dynamic interplay between seasonal temperature changes and shallow subsurface hydrological processes.