NASA's Curiosity Mars Rover

As you say if that was water / mud there would be a huge amount of excitement. They set up rules before landing in the event of discovering water or seeps etc that would require the rover to back away from the such area to prevent any bacteria etc that may have survived on the rover contaminating Mars. They could study such areas from a distance, but not perform contact science. However, the rover landed in 2012, and it would seem highly unlikely that anything from Earth could have survived that length of time in the temperature swings and radiation levels experienced by the rover, so those rules may have changed.

We'll get colour images in another day or so, but I think you'll see it's just rock with patches of sandy regolith. The large shallow depressions in the ground are thought to be formed by erosion resistant minerals that have been deposited by groundwater in the fractures in the bedrock surrounding the depressions. The science team are making measurements at each stop across these boxwork-like structures to confirm that theory. You'll get more detail in the mission updates posted in this community about the teams investigations and progress :)