NASA’s robotic geologist Opportunity is truly the little robot that could. With the original mission designed to last for just three months, on Saturday, February 17, it will celebrate its 5,000th Martian day of activity on the Red Planet.

Opportunity is solar-powered so NASA was not expecting the mission to survive the winter. This is why its primary mission had a length of just 90 sols (a sol is a Martian day). Opportunity landed on January 25, 2004, and proved to be a lot more resilient than expected; a true testament to the engineering capabilities of the team behind it.

"We've reached lots of milestones, and this is one more," Opportunity Project Manager John Callas, of NASA's Jet Propulsion Laboratory, said in a statement. "But more important than the numbers are the exploration and the scientific discoveries."

The golf cart-sized rover has, in fact, survived eight winters on Mars, contributing to important discoveries on the composition of rocks and soil on the surface of the Red Planet. It has also taken about 225,000 images, which are all available to view for free online.

Within six weeks of operation, Opportunity had found evidence that Mars used to have abundant water on its surface. It analyzed the composition of rocks, highlighting the mineral composition and their origin. It also delivered the first ever thermal profile of the Martian atmosphere, as well as conducting astronomical observations studying the occultation of the Sun by Mars’ two natural satellites, Phobos and Deimos.

"Five thousand sols after the start of our 90-sol mission, this amazing rover is still showing us surprises on Mars," added Callas. 

Opportunity was also the first marathon run beyond Earth, reaching the 42 kilometers mark back in 2015. But it’s traveling has not always been smooth sailing. For example, it was once trapped in a sand dune for 38 sols, which researchers named Purgatory after it freed itself. The rover has now driven over 45 kilometers (28 miles) from where it landed all the way to its current objective, the Endurance Crater.

It’s currently going down Perseverance Valley, a shallow channel in the western rim of the crater that goes from the crest all the way to the crater floor, where its work will continue. Although the rover has started showing sign of aging, there is still no end in sight for the mission.