Ie: mud volcanoes?

Aqueous outbursts due to volcanic heating of subsurface ice appear to have been extensive, nearly pervasive at various times in Mars' history, not just very early. Some of it must have been truly spectacular, astonishing events by any measure.

The 'water' that flowed in these outbursts nevertheless may have been strongly acidic/salty.

There appear to have been extensive mud flows and glacier action as well. Possibly still. Which leads one to suspect that less acidic/salty flows happen too at least occasionally.

My local paper said they knew it was water in the Phoenix samples because it "melted at 32º"! Uh... it melted? Really? As in liquified? That sort of puts a new wrinkle on things. We are conditioned to expect water to go directly from solid to gas on Mars, as CO2 does on Earth, even though there are plenty of areas on the surface where a liquid phase should be possible for at least a brief if not an extended time. If there is even a transitory "melt" phase for water ice samples at Phoenix's location, then there might be a very interesting situation. Time to dig out Robert Clark's posts on the potential of transitory liquid water on Mars and what it could imply.

If the ice is relatively pure (melts at 32º, after all) and it can have a liquid phase at the surface, even if only briefly, biology of some sort at the surface seems feasible albeit difficult.

If relatively pure water is bound in glaciers at the surface and saturates muds released from mud volcanoes, all sorts of interesting habitats suggest themselves. (Also gives an indication of where all these clay-like substances might have come from.)

Further, present polar locations are suspected to be only a few million years old; previous likely poles and polar deposits have been identified. Do they still have substantial ice deposits fairly near the surface? Be interesting to find out.