Curiosity has been investigating sedimentary rock around an area known as the Gale crater. The depth of the crater, and the fine-grained sandstone at the bottom hint at a large, lake-like body of water that remained over an extended period of time. This, in turn, adds fuel to the theory Mars once had the right atmospheric pressure, and a climate that didn't cause water to freeze. The question about water on Mars, of course, is really a preamble to the question about the red planet's ability to support life.
Curiosity's findings can't confirm life on Mars, but they do suggest the essential ingredients for biological soup (water and microbe-friendly conditions) were there. Theories and evidence for ground water on Mars have long existed, but usually based on the idea of subsurface water bursting up in a one-time event, or slower seepage to the surface -- or an ocean too saline for anything to live in it. This new data supports the idea of surface water far more conducive to the emergence of life. The team behind the findings claiming there's a "tantalizing possibility that extraterrestrial life might exist or have been preserved, because the evidence of water is so plentiful."