re: Polar pit gullies currently forming?
I agree that there is good evidence for active present-day formation of Polar Pit Gullies, but I dispute the role of liquid water. I still feel there is strong thermal evidence for gaseous CO2 as the active agent.
I haven't updated this older work of mine, but new images at higher resolution and measurements of temperature at key moments continue to support the model expressed here.
http://www.earthsci.unimelb.edu.au/mars/Polar.html
Note, in particular, the temperature data:-
http://www.earthsci.unimelb.edu.au/mars/Polar3.html