re: Curious fluid that thin atmosphere of Mars,
when it can form ripples in the sand just like water does on the beaches on Earth.
See the ripples in the bottom right hand corner of the picture in Buck Galaxy's post, it looks to me like liquid water had created them.
I wonder what color the sand at that area is.
If I was observing that type of a feature on Earth I would conclude that there was water at that spot very recently or that water is still there but the black and white picture does not show it.
Johannes