There's plenty to criticize about NASA but not when it comes to the study of Mars. Over the past decade, the agency has sent half a dozen or so probes to explore the planet. Two rovers are still sniffing around the surface, where they've already increased our understanding of Martian geology. The Mars Reconnaissance Orbiter, meanwhile, has only just begun to send back breathtaking high-resolution images from space. And now comes yet another probe: the Phoenix mission, above, to be launched in August, will land in mid-2008 in the Martian arctic. Scientists already know there's ice under the surface. It will be Phoenix's job to dig down, find it and try to figure out whether the Martian subsurface was ever or may even still be hospitable to some form of life.