What we initially conceived as a fairly simple geologic experiment on Mars ultimately turned into humanity's first real overland expedition across another planet. Spirit explored just as we would have, seeing a distant hill, climbing it, and showing us the vista from the summit. And she did it in a way that allowed everyone on Earth to be part of the adventure.

There's no way to actually turn the rover off.

Is there water still on Mars? I don't have a view on that because we don't have good data to answer that question. One of the biggest mistakes you can make if you're a scientist is to think you know the answer, or wish for a certain answer, before you actually have it.

The thing that sets Mars apart is that it is the one planet that is enough like Earth that you can imagine life possibly once having taken hold there.

The rocks, to a great extent, look swept clean. It's a much cleaner surface than what we had a right to hope for.

We have concluded that the rocks here were once soaked in liquid water. It changed their texture, and it changed their chemistry. We've been able to read the tell-tale clues the water left behind, giving us confidence in that conclusion.

I want to make as many people as possible feel like they are part of this adventure. We are going to give everybody a sense of what exploring the surface of another world is really like.