re: Galle Crater Scene
Yes, those dust devils are intriguing and they are exposing sedimentary rocks with there force that have been previously buried.
As far as the age of those gullies that's why I mentioned *meandering*. I'm no geologist but if I remember correctly natural watere ways that meander or snake heavily are indications of being older. If so this would indicate that water would have flowed for a long time there, albeit in ancient Mars time.
A matter for the professionals but it's very interesting to speculate.
SteveS