The denial that they're searching for microbial life is just canard, to keep those that don't follow these things from getting disapointed. They are most CERTAINLY prowling for signs of life, i.e. mineral deposits, aquatic depressions, dry rivulets, etc.
You misunderstand. They are, most certainly, searching for the existence of compounds. However, the rover is not equipped with technology capable of identifying microbial or fossilised microbial life.
Nightglade,I find it quite exciting as well,I don't think it's totally far fetched to think that Mars may have had forms of life that were very similar to ours,do you?
Who knows what the solar system looked like 4 billion years ago when Mars had oceans. Isn't it conceivable that the orbit of Mars was also different? Perhaps even inside the so-called 'habitable' zone. Another emerging theory out there, is that Asteroids are repositories for chemical compounds that serve as the building blocks for life. One connected theory is that similar life may have once existed on Mars, and asteroids that impacted the surface of Mars carried microbial life (which is capable of surviving in the cold vacuum of space) to Earth. If not life, then at least other compounds.
... this might be an interesting video for you.