How about MIMDDEN?
"Mars Is Dead and Dry Except in the Noachian"
This seems A little too pat for me although clearly mostly true. I keep forgetting if the Noachian includes the large impact structures Hellas, Argyre, Utopia?
Hesperia Planum, the standard measure for the Hesperian, is a volcanic provence. If Hellas is defined as the N-H temporal boundry and Hesperia is a result, then it still holds I guess.
Then there are the ~10-20 Mya terrain that WKH thinks are lava flows from Elysium...
How about MIMDDEN?
"Mars Is Mostly Dead and Dry Except in the Noachian"
Not quite as marketable as MEGAOUTFLOW but useable.