David Mayer posted this on the MSNBC board. It is probably the most reasonable short summation of the whole Mars question I have seen to date. I wholeheartedly agree, with one trivial exception: Number 4 I would modify as follows:

"...then life originated on Mars during that period [if it originated there at all].

But this is only nitpicking.

I have purposely avoided all the White Mars/Blue Mars/Purple Mars/Water/CO2 discussions, because they go into intensive details but are based on seriously limited data. Useful for discussion, but no real conclusions can be drawn. New probes are destined for Mars that will answer many of these questions.

I believe that one of the most useful things that could be done right now with a current probe, the Global Surveyor, is to identify locations where current surface geological/erosion/flow activity is suspected, and set up a program to take repeat shots of these areas at different times, in different seasons, and under different light conditions. I think such a program would answer many current questions.