Lest anyone get the wrong impression, I do actually agree with BRFelix on one issue, albeit in another message thread.

I think Nick is, shall we say, overly optimistic in interpreting the results from the Brown University - Vernadsky Institute Microsymposium as "support" for his views. True, the flavor du jour is for an "Iceball Mars," a model utilizing advancing and retreating ice sheets (i.e., global glaciation) and resultant melting of water ice to form some fluvial features. Even with convergence on the temperature issues, I really fail to see how that is "supportive" of the White Mars model. The vast majority of the scientists at the microsymposium do find CO2-supported flows plausible.

As to Blue Mars (e.g., Noachian era rainfall), I still believe it is a tenable model, notwithstanding the recent work of Colaprete and Toon. For example, see the (IMO) excellent paper:

Craddock, Robert A.; Howard, Alan D.
The case for rainfall on a warm, wet early Mars
10.1029/2001JE001505
23 November 2002

Abstract

Valley networks provide compelling evidence that past geologic
processes on Mars were different than those seen today. The generally
accepted paradigm is that these features formed from groundwater
circulation, which may have been driven by differential heating
induced by magmatic intrusions, impact melt, or a higher primordial
heat flux. Although such mechanisms may not require climatic
conditions any different than today's, they fail to explain the large
amount of recharge necessary for maintaining valley network systems,
the spatial patterns of erosion, or how water became initially
situated in the Martian regolith. In addition, there are no clear
surface manifestations of any geothermal systems (e.g., mineral
deposits or phreatic explosion craters). Finally, these models do not
explain the style and amount of crater degradation. To the contrary,
analyses of degraded crater morphometry indicate modification
occurred from creep induced by rain splash combined with surface
runoff and erosion; the former process appears to have continued late
into Martian history. A critical analysis of the morphology and
drainage density of valley networks based on Mars Global Surveyor
data shows that these features are, in fact, entirely consistent with
rainfall and surface runoff. The necessity for a cold, dry early Mars
has been predicated on debatable astronomical and climatic arguments.
A warm, wet early climate capable of supporting rainfall and surface
runoff is the most plausible scenario for explaining the entire suite
of geologic features in the Martian cratered highlands.

Received 11 April 2001; revised 10 April 2002; accepted 10 June 2002;
published 23 November 2002.

Keywords: Mars, Martian, erosion, climate, hydrology, fluvial.

Index Terms: 5407 Planetology: Solid Surface Planets: Atmospheres—
evolution; 5415 Planetology: Solid Surface Planets: Erosion and
weathering; 1815 Hydrology: Erosion and sedimentation; 1824
Hydrology: Geomorphology (1625).

Citation: Craddock, R. A., and A. D. Howard, The case for rainfall on
a warm, wet early Mars, J. Geophys. Res., 107(E11), 5111,
doi:10.1029/2001JE001505, 2002.