"This is kinda like the senior marathon runner who after a long run will ice up their knees and take some ibuprofen to get them ready for the next long run."
Distant target: The rim of Endeavour Crater is seen in the bottom-right of the image
Amazingly, this six-wheeled robot is about to celebrate its seventh anniversary on the Red Planet.
It's now covered more than 26km since its arrival on 25 January, 2004.
And remember, this was a mission [1.43 Mb PDF] that had the initial goal of surviving only three months on the surface.
Opportunity is well and truly "out of warranty", but it continues to roll - albeit backwards.
Engineers decided that putting the robot in reverse would help prolong its gearboxes by allowing their teeth to wear on the opposite side.
Opportunity's robot arm - the device it uses to reach out to interesting rocks - is increasingly "arthritic".
One of its joints no longer works properly and so, like an elderly human, the rover has to swivel its whole body sometimes to get the arm into just the right position.
Some of Opportunity's instruments, too, are worn and prone to anomalies. But the software equivalent of ibuprofen certainly seems to do the trick because this rover is on the cusp of what could yet be its most exciting days.
Within the past month, the rover has arrived at a crater on the Meridiani Plains that has been dubbed Santa Maria.
Opportunity was directed to this 90m-wide bowl because the Mars Reconnaissance Orbiter (MRO) circling overhead had seen some interesting rock outcrops.
Santa Maria should reveal more information about the period when Mars was getting drier and drier
It's difficult for the satellite to make definitive identifications of minerals on the ground because martian rocks weather over time and acquire a dust layer that hides many of the details of their true nature from the "spy in the sky".
Santa Maria would appear to be different, however. It's a fresh crater; it was dug out in the recent geological past and so MRO has been able to get a good look at the prospective mineralogy.
The crater has a strong signal for a particular type of magnesium sulphate (kieserite) which is likely to help Opportunity fill in the story it has been developing these past six years.
This story, written in the rocks of all the craters visited by the rover, tells us of a Mars that was probably losing its atmosphere about 3.8-4.0 billion years ago - a planet where acidic surface waters were in retreat. Ray Arvidson is the rover's deputy principal investigator. He told me:
"These craters are Nature’s drills to expose the bedrock. What we've seen throughout the history of this mission is continuing evidence that our original hypothesis is correct - that these are layered sedimentary rocks during what appears to be a drying-out period on Mars where occasionally there would be wet playas or lakes that would form mud, would dry out, the wind would blow, make sandstones, they'd accumulate, and then the ground water would come up and cement everything."
In other words, Opportunity is giving us a window on to the time when Mars was in the process of turning into the cold, dusty, desolate world we recognise today.
The rovers were designed for a three-month mission
But Santa Maria is just for starters. Six kilometres as the crow flies in a south-easterly direction is the 22km-diamter Endeavour Crater.
The impact which made this bowl has exposed even older rocks. These show evidence from orbit of clay minerals that were likely formed 4-4.5bn years ago in long-standing, neutral water.
This would be a window on to Mars' wetter, warmer past, a time when microbial life could perhaps have found conditions to its liking.
The clay mineral deposits look to be pretty big, covering a peak on the crater rim called Cape Tribulation. The peak is just visible to Opportunity when it looks to the horizon.
Will the rover make it to Endeavour after studying Santa Maria; will its systems hold out on the great drive?
Well, the signs are encouraging.
Santa Maria viewed from orbit: It was dug out in the geologically recent past
The "senior marathon runner" has managed more than 12km in just the past Martian year.
Nothing is for certain, of course, and you’ll notice I've made no mention in this post so far of Spirit, the other Nasa rover on Mars. Its seventh anniversary actually comes up before Opportunity, on 4 January.
Spirit is stuck fast in a sand trap, and has been in winter hibernation since March.
Sited at a higher latitude in the Martian Southern Hemisphere than is Opportunity, it doesn't currently receive enough sunlight to power its solar cells and communicate with Earth.
Callas and his team of engineers have long since given up hope of ever driving Spirit again, but they do want to revive the machine - if only to act as a static weather station. Callas told me:
"Spirit is located further south than Opportunity is, and so its winters are a lot deeper and tougher. We've always had to position the rover by tilting it so that the solar arrays point towards the north. We weren't able to do that so the rover didn't have enough energy to stay awake in the winter time and so it’s gone into a deep sleep. Our models estimated that at some point in the springtime the rover would power back up.
"The concern though is that the rover should have seen colder temperatures than it had ever seen on Mars, and that it would get below the nominal cold operating temperature for the electronics.
"There's a risk that the rover wouldn't survive the winter. We're listening now; we're listening every day to see if the rover would autonomously wake up and talk to us. We've also been actively commanding to the rover in case it’s in a potential alternative fault mode. But the period of peak solar energy production is going to be around the mid-March timeframe.
"If we have not heard from Spirit by then the likelihood of hearing beyond that starts to decrease."