This is surprising news...if you're living anytime before 1996. Since the days of the Mars Global Surveyor, it was obvious that Mars once had water. MGS returned images of gullies, topographic maps that showed erosion, and evidence of mineralogy that typically only occurs in the presence of water. So that Mars once had water is no surprise anymore. That it does have water was confirmed by both the European Space Agency's Mars Express mission and our very own Mars Reconnaissance Orbiter. In fact, data from these missions was used to determine where to land the Phoenix Mars Lander to increase the likelihood it would find water. And it did find water.
Finding water on Mars is not surprising news, but it is big news. Strictly speaking, the lander found ice, but ice is just one of the three phases of water. Oftentimes you'll hear NASA calling it water ice. That's like calling a Toyota an automobile Toyota or a tulip a flower tulip. The Phoenix Mars Lander did not find liquid water, which is what we usually think of when we hear 'water'. It found ice that it melted to produce water vapor whose signature it measured to confirm the presence of H2O on Mars. Yet stressing the discovery of water reminds us that Mars once had water and, by extension, that it once harbored the possibility of life. That's what makes Mars so interesting.
The Mars Phoenix Lander has fulfilled its mission and has been granted an extension in operations. However, there were unexpected problems and unexpected problems almost always lead to other interesting discoveries in science. For example, the Martian 'soil' did not readily fall into one of the several TEGA bins. Rather, it stuck to the scoop. Over time, exposure to the sun 'loosened' the sample enough that it could be deposited into a sample slot, but there was always the real possibility that any ice might sublimate away and never be explicitly discovered. That this did not happen is fortunate for us. However, problems like these lend support to the argument that robotic missions are not the panacea that some people make them out to be (Robert Park, for one). Robots are useful tools for exploring space and are much cheaper than sending humans with all their attendant life support systems into the unknown. Yet they are constrained in their ability to handle unforeseen circumstances. While some limited contingency can be built in, they will never replace the versatility of getting 'boots on the ground'.
Let me not diminish the significance of this discovery. Like I said, it is big - the biggest discovery all year, perhaps the biggest this decade. It should have its own cover on Time magazine. And it also opens up new doors in homeopathic research as well as opportunities for clean, bottled water that Fiji can't hold a candle to. Untouched by man, indeed.