Much of the Hellas surface looks very icy, as it probably should given its low elevation and relatively high latitude. There are usually clouds and fogs over the basin. Telescopic observers often mistake Hellas for the South Polar cap -- it can appear very bright and white.

The surprise for me is that the surface isn't more icy! There are plenty of flow signs though. Another surprise, too, is that there doesn't seem to be any evidence of flowing water in Hellas.

This image gives an idea of the general appearance of the Hellas Basin floor

Argyre, on the other hand, shows abundant evidence of glacial action. It's very clear, almost indisputable. And in winter, Argyre develops quite an icy coating, seems pretty thick, too.

Typical Argyre surface

Mariner Valleys seem much less "glacial" or icy. But that would make sense given the equatorial location. Instead we see what looks like evidence of standing water, lakes.

Here in Candor Chasma, for example

Now of course it could be due to wind!

Cheers B R Felix