Most of my ideas about early Mars are coming good these days. The realisation is dawning that Mars was only intermittently wet and mild, and those conditions appear to have been associated with continuing major impacts and with global volcanic episodes, NOT the status quo.

Vic Baker (in shades of the "Big Bang" insult) coined the snappy phrase "MIDDEN" - Mars Is Dead and Dry except in the Noachian. he set this up as a straw-man hypothesis that he could knock down with his volcanic-climatic-acme models of water flow and mantle plumes, but it has gradually come to be more and more apt as a description of mars aqueous history - or lack thereof.

It becomes even MORE interesting how we can have major floods on a dry and cold planet.

The only niggly question I'd suggest asking Alan is why so much effort is going into modelling aqueous flows with water as the active volatile, when we know that there is already an active volatile on Mars - CO2 and that it has an annual solid-vapour cycle that can easily drive flows of some sort under contemporary Martian conditions.

I would ask why effort isn't going into modelling and lab experiments on gas-supported flows to see how much of the gully morphology they can account for. At the very least, CO2 has to be ruled OUT before water can be ruled IN.

I'm not talking about violent outbursts of subsurface CO2 here - that idea has lost most of its legs, but the gas-lubricated springtime avalanche is still a very valid model for gullies.

Brown is a great department, and Jim Head a wonderful guy. We've had plenty of chats at LPSC over the years and he's very open-minded, but suitably cautious about crazy ideas. He's attracted a very dynamic group of young Grad students.

I wish I could join you for the Lunch, or the beers...