Hoffamn sez:

No aquifer

No water

No worries...

To which B R sez: "Not so fast, Mister!"

Unfortunately, there has long been a tendency to utilize all-purpose explanations for complex phenomena on Mars. Thus, for example, a researcher may say, "Ah ha! I suspect I know what is causing a specific channeling phenomenon on Mars, ergo all similar channeling phenomena are explained! Ta-da!"

Well. That's a downright Lowellian argument. (Much as I admire his observational ability, his arguments were... inadequate.)

Let us allow as how CO2 may participate in the formation of some channels on Mars, including the examples cited by Nick Hoffman on his web site. Let us further suggest that the channels cited by Robert E. B. may well be caused by CO2 and/or other volatiles. Let us go even further and suggest that many recently or annually formed channels on Mars cited by Malin and Edgett and many, many others may well be the result of water flows. Depends on when and where you look.

Many times I've suggested that researchers pay more attention to how water actually behaves on and under the surface of Mars instead of relying on anecdotal determinations that say "everyone knows liquid water can't exist on the surface of Mars; temperature and pressure too low." Conventional wisdom here is wrong, grossly wrong, but that hardly matters when someone has a point to advance which requires the near-impossibility of liquid water.

Turns out somebody found some very interesting results when studying the behavior of water under reasonably accurately simulated Martian surface and subsurface conditions. Robert Clark recently posted a link to one such study on sci.astro.

http://adsabs.harvard.edu/cgi-bin/bib_query?1989LPI....20..666M

As temperatures were raised to the neighborhood of 273K the following appeared: Circular depressions, pools of standing liquid water geysers, outflow, no ice surface caps, wide source, narrowing as the fluid evaporated... familiar phenomena given what we see on the surface of Mars.

I'm sure Nick is familiar with this and other experiments.

Water is no doubt a significant participant in channeling on the Martian surface.

But here's a question: why would active water on the Martian surface be cause for "worry?"

Cheers, B R Felix