The goal of the Curiosity rover is to study the history of Mars. It was to see whether Mars has, or ever had, an environment able to support microbial life. It indeed did that, finding evidence that 3 Billion years ago there was once water and a life-supporting environment. It is important to know that it found that life COULD HAVE existed, not that it certainly DID. It will also carefully look at samples scooped up from the soil and drilled powders from rocks.