After six years on the move, NASA's Mars Exploration Rover Spirit prepares for a new phase of science.

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(music)(John Callas)For a 90 day mission, I remember when we landed we were excited, we would have three months to explore this region around our landing site... and we've basically blown the doors off that.You know for six years now we've been doing classic field geology on Mars, learning about the planet and its ancient past... and there have been powerful revelations that have come well after that prime mission.(Scott Maxwell)This experience with Spirit is something that I've really kind of integrated into my whole identity.You know, this has become part of what I do. And it looked, at the very beginning of the mission,like this was going to be something that I got to do for a very brief time, for three months.And that was terrific, and it was unique, and it was special, and I was really looking forward to it --and I never in my wildest imagination believed that it was going to go one for five years!(Ashley Stroupe)Spirit has really had to have a lot of "spirit" to keep going.It's been the little rover that could, in a way.It's had to work very hard for all of its discoveries.Two Years into the mission, well passed the prime mission, the right front wheel stopped working... and the wheel doesn't spin, so when we drive we drive backwards, dragging that wheel. And it would cut a furrow.And so it actually turned out to be yet another scientific instrument or scientific investigation... because it now trenched as we would drive along, revealing what's just beneath the surface. One thing that we seem to be finding almost anywhere we're digging this trench are these widespread deposits of various kinds of salts and minerals.They look this brilliant white or yellow in the color images.And that's because they're either sulfur or silica or salts of various kinds.And the really important thing about these minerals -- and salts in particular -- is that the only way they form is with water.So the fact that we're finding these salts is real evidence that there was hot water over a very widespread area -- not just little isolated pockets.Mars really could have been a place that supported life.And without these rovers driving over these vast distances, far beyond their expectations, we would never have known that.That's one of the great discoveries that Spirit did, well after its prime mission... and as a result of one of the most serious mechanical failures we've had on either rover.Mars is a pretty harsh place. We've had dust storms before; we've had really low power situations in winter; we've had other small glitches that have caused us some tense moments, but Spirit seems to always find a way of turning some kind of adversity into something positive.(music)(John Callas)April of 2009 we were driving on the west side of Home Plate... after we were unsuccessful in trying to go other ways around Home Plate.And the rover broke through what I would describe as a perfectly camouflaged "tiger trap".We were driving on terrain that we had successfully driven on before, but suddenly... the rover broke through a crust and was now embedded in some loose, soft material.It's almost like quicksand for the rover, and with just five wheels spinning... the only thing that was happening was the rover was sinking deeper into this material.So we stopped, and we did a very ambitious ground test campaign... where we built a sandbox on the ground and used one of our engineering rovers... and experimented with techniques trying to get the rover unstuck.The reality is, it's very difficult with just a five wheel rover to get it unstuck from this difficult predicament.(music)(John Callas)We have a very ambitious stationary science campaign for the rover.For six years we've been driving both Spirit and Opportunity, not really taking any time to stop and 'smell the roses'.There's a lot of lander science that one can do, and we plan to do that with Spirit.Spirit's continued triumphs absolutely amaze me!Just the fact that we've had so much more of this mission then we ever thought we were going to have.What these rovers have done is that they have made Mars a familiar place.Mars is now our neighborhood. My team goes to work on Mars every day.And that I think is the great, intangible contribution of these rovers... is that Mars is no longer this strange, unknown world.Yes, it's still mysterious, but much of Mars is now known to us as a familiar place.(music)NASA, Jet Propulsion Laboratory, California Institute of Technology