Recurring Ice Ages at Martian Mid-Latitudes Evidenced by Characterizing Double Layered Ejecta (DLE) Craters

Mars has undergone massive shifts in its spin-axis obliquity, which have caused cyclical climate changes resulting in the mobilization and redeposition of water ice between low-, mid-, and high-latitudes. The duration of ice ages in the Martian mid-latitudes is governed by periodic changes in obliquity. Although numerous geomorphic features indicative of mid-latitude ice ages have been reported, the temporal patterns and chronological extent of the mid-latitude ice ages (synonymous with periods of higher Mars obliquity) remain unclear. To address this issue, we used crater size-frequency distribution (CSFD) techniques to investigate 142 double layered ejecta (DLE) craters located in the mid-latitudes (30°–60°) of the northern and southern hemispheres, which are interpreted as being associated with icy substrates and recording mid-latitude ice ages. The dated 142 DLE craters have absolute model ages (AMAs) ranging from ∼4.5 Ma to 3.5 Ga, with their distribution pattern showing several pronounced peaks, suggesting that the Martian mid-latitudes have experienced multiple prolonged high-obliquity-driven ice ages over the past 3.5 Ga. The youngest DLE crater has a model age of ∼4.5 Ma, which aligns with the most recent major Martian obliquity shift (from average ∼35° to 25°) predicted by obliquity simulations to have occurred between ∼3 and 5 Ma. This suggests that the change of Martian obliquity from high to low average over the past 20 Ma has likely inhibited the formation of DLE craters in mid-latitude regions.