What's the current 'conventional wisdom' about liquid water
below the surface of Mars? I recall papers at LPSC's of the
last decade that speculated on pole-to-equator liquid water
percolation through regolith between solid basement rock below
and frozen permafrost above. So far Mars Express is finding
lots of buried ice, but no traces of liquid water, not even 'wet soil',
or so I hear.

And -- what are plausible sources of the hydrostatic pressure
that now seems to blow out the ice/permafrost plugs at the
surface and allow surges of mud from time to time. Why should
there be any pressure at all, much less enough to break through a
dam? Is evidence for episodic metabolism staring us in the face?