Alex,

Responding to your comment:

>As you noted, MOC NA imagery has cast a bit of doubt on *accessibility* to the putative lacustrine deposits,

[snip]

>not whether Gusev ever contained a closed body of water, something that most Mars scientists agree was the case

Please see the following:
http://mars3.jpl.nasa.gov:80/mgs/msss/camera/images/7_17_98_gusev_rel/index.html

The relevant text is:

At 12:17 a.m. (PDT) on April 24, 1998--during Mars Global Surveyor's 259th orbit--MOC obtained the high resolution
image of Gusev Crater and Ma'adim Vallis shown above, in part to test some of the proposed hypotheses. The raw image
has a scale of 7.3 meters (24 feet) per pixel. At this scale, there are no obvious shorelines that would indicate the past
presence of a lake in either Ma'adim Vallis or Gusev Crater. There are several alternative explanations for this absence,
including:

It is possible that any lake in Gusev occurred so long ago that erosion by wind and hillslope processes have long
since removed such features.

It is possible that 7.3 meters per pixel is insufficient to identify key diagnostic lake features.

It is possible that a lake once existed, but that shore- and near-shore processes as they occur in terrestrial lake
environments did not occur on Mars.

It is possible no lake ever existed.

Gary