Greg wrote:
Some have channels [that are] reminiscent of fluid outflows, unusual given the high latitudes.

Alex writes:
One has to be careful with an overly general statement like that. There is abundant evidence for fluid flows at near polar latitudes. Indeed, even on top of the current southern polar cap there is evidence that catastrophic outflow(s) created Chasma Australe, a 500 km long and up to 80 km wide erosional reentrant that is carved into the polar layered deposits. Most workers (including myself in my Ph.D. dissertation, see strong evidence of erosional and depositional features arguing for a flood origin. For another example see a recently published paper:

Head, James W., III ; Pratt, Stephen 2001
Extensive Hesperian-aged south polar ice sheet on Mars: Evidence for massive melting and retreat, and lateral flow and ponding of meltwater
J. Geophys. Res. Vol. 106 , No. E6 , p. 12,275

The key is "when" (i.e. epoch) such fluids (presumably water, but possibly something else) acutally flowed. Orbital obliquity excursions, polar wander, chaotic climate shifts, etc. all affect the spatial and temporal distribution of such fluild outflow features.

Alex R. Blackwell
University of Hawiai