[Axenolith]

At the time of the Vikings (the probes) we should have begun altering Mars to make a manned mission truly worth while. The pocket protector wearers might get a lot of good research out of probes but the masses aren't going to continue to support it unless there's some hope of eventually settling some people somewhere off world. There's enough water there to cover that globe in 300 feet uniformly (i.e if smooth) and between that and the frozen CO2 you could get enough pressure to equal Everest altitude at low elevations, enough to work in a warm suit with supplied O2.

We could have changed the albedo of the poles with a few well placed impacts then, but now we'd probably have to file the mother of all EIR's and hand wring over some hypothetical unicellular hanger-on that refused to 100% crap out when the carbon cycle went bust there...

[ElkGroveDan]

Agreed. I think a few genetically engineered photosynthesising algaes would begin to work wonders there. Terraforming is not a job for the faint of heart, and it takes time. Let's get going!