That second bit still seems a bit of a leap to me, and to be fair we havent yet established the exact nature and cause of these avalanches, or what relation they have to the channels. It also seems a bit naive to me to assume all the gullies formed the same way, dry granular flows are also a convincing alternative.And the report I read mentioned CO2 frost, not a CO2 icepack, implying to me that the dominant volatile here is most likely H2O. FWIW though the white mars theory has been gaining ground, at least in forms that permit liquid water under excepional circumstances or as thin films, for a good few years now, so kudos to nick anyway.