The target beneath the tool turret at the end of the rover’s robotic arm in this image from NASA’s Mars Exploration Rover Opportunity is “Private John Potts.”

When NASA scientists landed Opportunity on Mars on Jan. 24, 2004, they expected the rover to last for three months.

Opportunity has far outlived its life expectancy, still going strong twelve years later.

And keeping Opportunity alive and moving hasn’t been easy for NASA scientists. Opportunity’s batteries are powered by its own solar panels, an elusive energy source during dark and windy winters.

“Cleaning events have become a critical, yet unplanned component of long-duration solar powered missions on the Martian surface,” explains Discovery News. The rovers’ drivers on Earth optimize windstorms to clean the dusty panels. “Opportunity’s most recent cleaning event occurred toward the end of 2015, before it plunged into Martian winter, thus allowing the rover to continue its valuable work into 2016.”