NASA thinks the hydrated salts at RSL sites they detected from orbit are evidence of flowing salt water on Mars. I think a better theory is that frost is blown into cornices at the crests of hills and these then make avalanches when they warm up. A cornice can lose structural strength as the temperature rises even before it melts, making an avalanche. The trails on Mars all start near the crests of hills, which makes sense for cornices but not for random salt deposits. The trails sometimes cross, which happens for avalanches on Earth but not for liquid water runoff. At the rate that salt could absorb water from the thin dry air on Mars it would probably just soak into the ground and not flow downhill. The trails are fixed width, which fits with cornice avalanches but not flowing water. There is no method for the salt to get back to the top of the hill. There is evidence of long term erosion that could not be done from a fixed amount of salt absorbing water from the air. Deep paths in rocky cliffs take time. Cornice avalanches could have been happening for millions of years.