So said Prof. Steven Squyres last week about Opportunity, the rover that keeps on ticking. Now 7 years and 20 miles outside of warranty, Opportunity has reached what is almost sure to be its final destination: Endeavor Crater. Already, the plucky rover is turning up new discoveries, such as a breccia with unexpectedly high levels of zinc and bromine. Those elements in that type of rock suggest a hydrothermal ore deposit. That would be yet another line of evidence of water on ancient Mars, suggesting an environment that was habitable at least some of the time. A spectacular home stretch for an already spectacular mission.