Evidence for Hesperian glaciation along the Martian dichotomy boundary

Here we provide geologic and geomorphologic evidence of Hesperian glacial activity along the Martian topographic dichotomy in Aeolis Mensae. Our geologic investigation focuses on a fretted plateau unit with networks of deep, flat-bottomed valleys, some of which extend from cirque-like scarps. Based on cross-sectional elevation profiles of the valleys and the resemblance to terrestrial analogue features, we propose that these fretted terrains were dissected by outlet glaciers emanating from the dichotomy boundary. The fretted terrains are spatially and temporally linked to deposits with concentrically ridged lobate fronts, providing evidence for ductile flow along a canyon floor, similar to debris-covered glaciers found on Earth and in other glaciated regions of Mars. We estimate a minimum thickness of 1500 m for the ice cover in that region during the Hesperian, equivalent to recent mid-latitude glaciations in other parts of the dichotomy boundary. Collectively, our observations suggest that glacial activity could have been an important mechanism of modification of the topographic dichotomy boundary since the Hesperian.