Unabashed support? Hmmm... I guess that's what I get for trying to have an open mind. In fact, I think that, though Nick's model has many persuasive points and certainly deserves serious consideration, he goes too far. In fact, I feel much as you do, Alex - "I don't accept it at this time", or perhaps "I don't accept it as a complete explanation at this time".

I have spent a fair bit of time looking through Nick's site, thanks, but some questions remain unanswered. Part of this, I imagine, is because Nick's hasn't had time to complete the site... when reading "the story of the Red Planet without water" one reaches the page:

http://irian.geology.latrobe.edu.au/~nhoffman/Mars/Cryo.html

where the answers to some of my questions might have been answered.

Maybe I'm missing something - it's happened before - but I fail to see anything on Nick's site to explain where the enormous amount of CO2 would come from all of a sudden to cause the channel excavations in one fell swoop. Large canyons on Earth have been formed over fairly long time periods involving water cycling through the system, but Nick's CO2/clathrate eruptions don't seem to have any comparable cycling mechanism and so would have to do their thing all at once, which seems a lot to swallow, even at Mach 0.5.

Besides, not everyone reading this board has the time or inclination to sift through all the referenced sites; sometimes (IMHO) it's worthwhile to ask quesions to which one might knows the answer, in order generate on-board discussion.