No one yet knows if there is life on Mars. The discovery that ancient Mars probably had liquid water on its surface means that the conditions for life probably existed at some time in Martian history. But what about the present? Could there be life on Mars now? The strategy for Mars exploration is to send robotic explorers that first look for signs of past or present water, which is necessary to life as we know it. In places that had long-term water or still might today, the next step is to look for carbon-based molecules called "organics," the chemical building blocks of life. Places where both water and organics exist may provide a possible environment for life to thrive--in other words, possible habitats. Orbiters, landers and rovers sent to Mars so far have made a lot of progress on finding evidence of past or present water. Mars exploration is entering its next phase of looking for organics. For example, the rover Curiosity is on its way to Mars now and is scheduled to land at Gale Crater on Mars in August 2012 to look for signs of that and more (http://mars.jpl.nasa.gov/msl). Once we find possible habitats, future Mars missions would then likely be sent to look for signs of past or present life itself.