Ongoing flow activity was highlighted a few years ago on Mars by high-resolution cameras. Various flow types have been identified (new channels, dark lineae, bright deposits…) but there is still no consensus about possible formation mechanisms: dry avalanche? liquid water? carbon dioxide ice? A study conducted at the Institut d’Astrophysique Spatiale reveals for the first time the composition of winter ice forming in association with flows. Results suggest the coexistence of several current formation mechanisms.