A related question about water flows Options

[Paul Murphy]

hi:

I'm actually a lurker on this site because I don't generally understand the issues discussed but
find them interesting anyway. That said, there's a question that I can't seem to find the answer to
and hope you guys can enlighten me on.

The general discussion of water flow effects, particularly with respect to canyon and chasm images, seems to attribute some very deep surface markings to water erosion. The recent spate of ESA images showing the Echus Chasma, for example, generally claim those cliffs are up to 4,000M high and that they were created by water flows. So my question is: if features like these are largely the result of water erosion, how long did it take and what volume of water was involved?

Rock is rock here or there, and the rate of water erosion has to vary (I think) with the square of velocity of the water/grit mix running over it - and since that velocity on Mars has to reflect Martian gravity, not Earth's, it should have taken much longer (or needed a lot more water) than here. Yet geophysical instability here has meant that we don't have features that size on earth (to my knowledge anyway) - so what does this tell us about how much water Mars had, and for how long