Global inventory of water-ice related landforms in gullied craters on Mars

Martian gullies are landforms consisting of an erosional alcove, a channel, and a depositional apron. Gullies and water-ice related landforms, such as concentric crater fill (CCF), latitude-dependent mantle (LDM), moraine-like ridges (MLR) and glacier-like flows (GLF) are both common in the midlatitudes on Mars. Gullies have been found to form in, and interact with, water-ice related landforms, but to what extend the (past) presence of water-ice may have affected gully formation remains unknown. 

This work investigates the association between gullies and water-ice related landforms in gullied craters on Mars. We use a tick-box approach to classify gully type and the presence of CCF, LDM, MLR, and GLF in 3314 gullied craters on Mars identified using CTX imagery. 

Results show that 89% of gullies are currently incising into soft sediments, while 11% are currently incising into bedrock. CCF is found in 60% of gullied craters, LDM is found in 59% of gullied craters, MLR are found in 18% of gullied craters, and GLF only occurs in 5% of gullied craters. Interestingly, for the gullied craters where MLR is present in 69% of the cases gullies are exclusively found above the MLR and not on other slopes.  A sharp delineation has been found around 40° N/S for both CCF and LDM, with both occurring above the 40° N/S line, which coincides with the change in orientation in gully orientation from pole-facing below 40° N/S and with multiple orientation above 40° N/S. 

These results show that interactions between water-ice and gullies could have been common on Mars. Further study is needed to determine if melting of the water-ice deposits can have contributed to the formation of some gullies, or if slopes preconditioned by water-ice activity (for example by forming deposits of loose sediments) are favorable sites for generating gully activity by CO₂ sublimation.