Not so fast, Bruce...
I thought we decided to let the Noachian rest for a while.
I haven't "agreed" anything yet, just deferred detailed anysis until I have time to get to grips with it.
For what it's woth, I think my ephemeral atmosphere story does still have legs (paradoxically, for the very reasons you claim it doesn't - but we can do that discussion again sometime later)
As for modern Mars, the concept of liquid water a mere 1 km down is pure pipedream. The heat flow, surface temperature, and the mulling effect of clathrate on brines mean that at the equator one expects liquid water at 7 km.
Drill for that!
Oh, and watch out for the CO2 blowouts on the way.
Item 3 and read the rest while you're at it.