Looks like there is at least one NASA website dedicated to planetary atmospheres, that cares not a zilch about the greenhouse effect.
The Planetary Atmospheres Node (Atmospheres Node, or Atmos) of the Planetary Data System (PDS) is responsible for the acquisition, preservation, and distribution of all non-imaging atmospheric data from all planetary missions (excluding Earth observations). The primary goal of the node is to make available to the research community the highest quality data possible. To this end, data are reviewed and re-formatted where necessary in order to meet the documentation and quality standards established by the PDS
CO2 and “greenhouse” are vaguely mentioned in few of the Abstracts but for some reason haven’t made it to the Education pages.
ADDENDUM: I am discussing the above with Ed Darrell at his Millard Fillmore’s Bathtub.
ADDENDUM (2): It seems that we have an answer. That site doesn’t mention the GH effect because no interplanetary probe has bothered yet to study it. Things may be a-changing with ESA’s Venus Express.