Check out our new paper in @nature. We show that at least 25% of the total martian valley network volume formed from catastrophic lake breach floods (1/10): nature.com/articles/s4158… Valley networks on #Mars are somewhat analogous to river valleys on Earth but differ morphologically. Maybe this is a sign that instead of forming from precipitation, #martian valleys are a result of groundwater or glacial erosion, or even lava. (2/10)