Re: I have to say that the "valley's" entering the crater ...
Actually it does look like a fluvial system and that can and does include sand dunes to a leyperson.
It doesn't prove water per se, but does prove air currents. However the 'clast' and visual aspects of the photos are very similar to evidence found on Earth so an assumption they were formed the same way is a fair estimate based on a 2d image. It could be water, but could also be just air formed.
The clast composition and formation however could well prove water as that is how they can be formed. Given the 'blast' effect ony cleared a small area and there isn't much top surface would suggest there is either really strong winds (not much depostion of sediment) or not much dust around to settle (what is deposited is a thing layer), or just not much movement by wind which might suggest more water formation than wind.
Just a few images and you can use existing knowledge to determine tons of stuff, I bet geologosts and geographers will be wetting themselves over the next few months, very exciting stuff.
I base my assessment on a Dual honours degree in Geography and Geology, including a semester on Martian topography and geophysics.