I'm not a geologist and so I would fall easily in any trap on that subject.Regarding your question, I don't think that there is a proven hydrology in those areas of Mars.But I strongly hope that they will find traces of water very soon.What a pity that Spirit and Opportunity can't dig deeply into the marsian soil.In any case, those images, scientifically reprocessed ( and congratulation once again for your work rlb), are great.I agree to say that the stones on Mars have an oxydation level that we don't encounter on Earth.