...and one I obviously should have considered.

I guess I should better familiarize myself with non-oceanic explainations for the formation of the northern plains. I've seen a few, which I felt were not at all convincing, but I'm sure that more are out there. Later today I'll read the paper that Greg posted, and see if that can illuminate me.

On a tangent: if these findings spell the death of the paleoblue Mars theory, what do they mean for any future Blue Mars? Can a White Mars be terraformed? There is obviously a tremendous amount of water there, but most terraforming strategies have relied on CO2 being released by the carbonates, after being warmed by a small artificial greenhouse effect. But if the carbonates aren't there...?

Cheers,

Nathan.