Roving across an alien landscape isn’t easy, but NASA’s Mars rover Opportunity has proven time and time again that it is the reigning champion of Mars off-roading. Alas, all champions have their limits and it looks like the veteran robot has met its match.

PHOTOS: 12 Years On Mars: Opportunity’s First Sols

While exploring the slopes of “Marathon Valley” on the western edge of 14 mile-wide Endeavour Crater in Meridiani Planum, rover drivers at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., made the bold decision to command Opportunity to climb the most extreme slope it has encountered in its 12 years of exploring Mars.

In an attempt to reach a target near the crest of “Knudsen Ridge,” the 6-wheeled rover had to surpass a 32 degree slope on March 10. Anticipating some slippage, the rover’s route planners added many more wheel rotations to cover the distance. To climb a hill, Opportunity wasn’t afraid to do what it takes to scramble up the slope.

On the third attempt, after the planned wheel rotations were completed, the tenacious rover only managed to edge 9 centimeters (3.5 inches) up the hill. The commanded wheel rotations would have driven Opportunity 20 meters (66 feet) on a flat surface without slippage, so it was clear that Opportunity had spun its aluminum wheels into the dusty surface and the JPL team decided that this was one hill too far and planned an alternate route to a new target further west.

PHOTOS: 12 Years On Mars: Opportunity’s Top 5 Revelations

Since then, Opportunity has carried out 8 drives, including a reverse maneuver back down the hill for 8.2 meters (27 feet) and then back uphill for 60 meters (200 feet) toward its new objective.

Interestingly, Opportunity turned the Marathon Valley retreat into a chance to clear some dust off its solar panels. “Shake it off! Opportunity attempts steepest climb. Drive tilt/vibration dusts solar array,” the rover’s official Twitter account tweeted on Thursday with a photo showing streams of dust slide off its top deck:

NASA/JPL-Caltech

VIDEO: Drive With Opportunity on Epic Mars Rover Marathon

Opportunity took this latest challenge in its stride, and that insurmountable slope is a distant memory and the change in plan shouldn’t impact its mission objectives. Both the intended and alternate targets hold interesting clues to Mars’ wet past. Guided by its satellite buddy, NASA’s Mars Reconnaissance Orbiter, Opportunity has been zeroing in on clay deposits detected from orbit, basically minerals that could only have been formed by the sustained presence of surface water on ancient Mars.

While the rover may be showing signs of old age, it’s certainly proving that it’s no slouch, showing us all that it will at least attempt any challenge Mars throws at it.