According to Wikipedia the Context Camera(CTX) on board of the Mars Reconnaissance Orbiter had already mapped 50% of Mars by Februari 2010.
Should it not have to be possible to get access to all these images in a logical way ?
Page 13 of this presentation of the Second MSL Landing Site Workshop shows a mosaic of CTX images P04_002746_1808_XI_00N002W_070226,
………. P05_003168_1825_XI_02N002W_070331 and
Is it possible to get these images with those identification numbers ?