...isn't so big in the end. Tony Colaprete and I get on quite well - he's one of the "bad boys" of Planetary science too. He isn't afraid to upset anyone's applecart with solid scientific reasoning.

The difference between us is that he starts off with a CO2 atmosphere fully "inflated" while I start with a significant reserve of frozen CO2. he concentrates on adding water to the existing CO2 atmosphere, while I use the water passively within a strongly-varying CO2 atmosphere.

Of course, it rains on my early mars as well as on his. mine is a bit more interesting because it can flick between a CO2 iceball and a warm moist planet, with intervals of CO2 rain at times, as well.

I haven't done proper modelling of my imagined early Mars but he has, for his. So scirntifically, he's on more solid ground. I just think he could have more fun if he opened up his model parameters a bit to include the phase changes of CO2.

Whichever one of us is "right", we're both pointing to a planet where the early climate was NOT reliable and steady-state but unreliable and downright catastrophic. Most scientists don't like catastrophism, even at a time in the early solar system when catastrophic impacts were "normal"! As a result, neither Tony nor, especially, I are much in favour. But at the same time, the new ESA mineral mapper results are putting large nails into the coffins of those who insist on a regularly or recently wet Mars.

As I say, time will tell...