Two representatives of Mankind, or at least of publicly funded science, have been bravely toiling long past their stop-loss date on the cold and airless Martian desert. Both Spirit and Opportunity are arthritic and clumsy, losing sensitivity and capability.

January will be the 4th anniversary of their arrival. I remember the pictures they took after they descended from their lander ramps and turned to look back at the little platforms. Something wistful about the view--a one-way trip with a short expected lifetime of 90 days was the future they faced.

Unlike the replicant in Blade Runner that laments "No one will know what I have seen", we are present inside the rovers. They are actually robots, not being driven by us but only trying to complete our commanded tasks.

It must cause some pain to engineers at the Jet Propulsion Lab to direct Spirit to drive in reverse, so it can drag its defunct right front wheel. Opportunity has a front wheel that works but doesn't steer. That rover has a touch of bursitis, reducing the torque it can deliver with its instrument arm.

Both rovers have lost touch sensitivity as the encoders on their rock grinders gave out. Now they can grind but can't feel whether the tool is turning.

Sometimes you get lucky. The major expected challenge would be maintaining power to keep instruments from freezing, in spite of dust buildup. Conveniently, dust devils or other wind gusts have periodically scoured the solar panels on the rovers, and they usually are putting out around 90% of capacity.

I have an image of an amused alien taking pity on the cautious and sluggish rovers (slower than a tortoise, by design), and sneaking up on the blind spot to sweep off the fine Martian dust. Then the alien leaves and checks back in a few days to see the rover has moved about twenty feet.

When Spirit and Opportunity come to a complete halt, perhaps our helpful Martian will give them each a small burial cairn. More likely, in the real future we will eventually find them, as we stand present in person (if in pressure suit), and mark their efforts.