Phoenix is well on its way to Mars. This site, http://phoenix.lpl.arizona.edu/mission.php, talks about the mission itself, mostly being a lineup of credits from some of the most important (or at least highly ranking) people. The site also details organizations and other contributors to the project, and this time there's actually a serious Canadian contribution. Information on landing site and broad objectives are detailed. So what exactly is there to find on Mars? Hopefully we'll figure that out.
The Viking missions have already been there, though they didn't find much. There are some interesting finds (such as methane, deposits, soil systems, and frozen water) that can suggest the presence of liquid water or life, but it isn't as if they couldn't have been caused by other things, as critics to these theories have noted. With a very low atmospheric pressure relative to Earth's, combined with very low temperatures and the fact that we're having one hell of a time finding visible, liquid water that didn't just fizzle into gas or freeze, life won't be straightforward to find, if it's there. What happens if this mission fails to find life, anyway? That's a question just like if it does pretty much assert that there is, in fact, some form of life, ending that debate. If there's more inconclusive evidence, then will there be another Phoenix mission? Meta-Phoenix? Imagine what would happen if we were to establish permanent residence on Mars and find, after many expensive failures, that there was no life on Mars. Alternatively, it would give us some faith in pursuing such goals if life was found that wouldn't be passive to our serious invasion. If we do find something like life on Mars, will it have all the traditional characteristics of life on Earth, or at least all of the fundamental ones? Might this theoretical life prove to behave as life, but have no genetic code as we know it, or no cellular structure?
In the end, I don't think that, relative to our capabilities, finding life on Mars would have been such an epic and consuming search compared to where we could have had to go, in this scenario. Other solar planets, masses, and beyond are massively more difficult to reach than Mars, even with just robots, as I've repeated incessantly. May the next question be: is there life outside of our solar system? Outside groupings of stars we're in, our area of the galaxy, the galaxy itself, our group, etc? I don't know what would lead the universe to create life restricted in some odd way to a star cluster, but we really don't know yet.