What have we learned since Viking?

From MarsDaily here:

First, there's the unsung hero - the Mars Global Surveyor, the mission no one's ever heard about. It did a fantastic job. Its orbital laser altimeter gave us a sense of the elevation everywhere on Mars. It basically gave us the globe we have today and the sense of what we're doing. It also had a thermal emission spectrometer on it, with which we identified a possible water-laden mineral of hematite. That then became the fundamental piece of information from which we made the decision to land at Meridiani with one of the two Mars Exploration Rovers, and that of course is where we found the outcrop and the first initial sense that there had been water there for a long period of time. So all these things are tied together.

Pathfinder, from a scientific history point of view, did not add much, but that's not important. Pathfinder re-engaged the public. Following that, there was an Odyssey mission that took gamma ray spectrometry and determined with its neutron detector that there was water pretty close to the surface in lots of places, and then we had the most recent mission, the Mars Exploration Rovers.

There's one mission that in the United States has not received as much play as it should have. If you spend any time in Europe, you know how jubilant they are about the successes of Mars Express. Mars Express has been in orbit for a couple of years, and it has made some fundamental discoveries. I'm not going to enter the debate about whether or not methane has been found. They announced that they found methane and other people have announced that they didn't, but nevertheless it is at least an interesting scientific puzzle that needs to be worked out.

What I am the most surprised and delighted by are the observations made by the OMEGA spectrometer, which has identified not only the sulfates, of the hematite variety and many different kinds, but also what are called phyllosilicates, or clay minerals which, the geologists tell me, means there had to be standing water for extended periods of time. So the Mars Express observations have set up a new picture of the evolution of the planet. Once again we have a new Mars that has emerged.

Think about it. A new Mars emerged in '71, with the Mariner observations. A new Mars emerged with Viking. Another one with Mars Global Surveyor. Another one with MER. Now still another one with Mars Express.

We are so lucky. This is only going to happen to us. Five hundred years from now, maybe someone will be finding something new about Mars, but it'll be some rare, isolated discovery. What is happening in our lifetime is the emergence of another world. It has given us the ability to think about what we are, and who we are, and where we are going in a way unlike we've ever been able to do before.

Did life start on Mars? If not, why not? If so, was it knocked off of Mars and carried to the Earth, and perhaps formed the beginnings of life on Earth? These are wonderful puzzles, and as the days pass, we're learning more and more about how to answer them."