There is a great deal of debate about the presence of liquid water on Mars, and there are alternate interpretations of the evidence. Liquid water would boil immediately at those temperatures and pressures, but if there were enough of it, the water could flow for some distance. Alternately subliming carbon dioxide could also cause flow-like features. This debate is completely out in the open, and none of it is hidden. I think both processes are occuring, at different times in the orbit, and/or at different latitudes, and/or at different times in the ancient past when Mars had varying degrees of obliquity; but once again, none of this is hidden knowledge.