Mars Rovers Keep Going And Going On Solar Power, So Why Can't We?

This recent article about the Mars Rovers got me thinking:

NASA: Mars rover ready to enter crater

WASHINGTON, June 28 (UPI) -- National Aeronautics and Space Administration scientists said the Mars rover Opportunity is ready to descend into that planet's massive Victoria Crater.
The latest trek presents a high degree of risk for the long-lived robotic explorer, but NASA and the Mars Rover science team expect it to provide valuable data.

Although NASA has planned the descent to enable an eventual exit, scientists said Opportunity might become trapped inside the crater or lose some capabilities. The rover has operated more than 12 times longer than its originally intended 90 days.

Now when NASA designed the Mars Rovers, they did not consult ExxonMobil about powering the rovers with fossil fuels. No, NASA wanted something more sustainable and advanced.

It seems to me that we could learn from NASA's good example. The Mars Rovers prove that we have the ability to convert to renewable and enviromentally-friendly energy sources, and the threat of global warming provides the necessity.

What are we waiting for?