NASA’s Curiosity rover has been exploring Mars for more than four years. The rocky landscape on the red planet has started taking a toll on the rover’s wheels. Even though Curiosity has traveled just 16 kilometers since 2012, one of its wheels has begun to wear out. Its wheels are made using super solid aluminum. The US space agency detected the breaks in the wheel treads on March 19 during a routine inspection.

Curiosity rover NASA
Image Source: NASA / JPL / Twitter (screenshot)

Only one of six wheels is damaged

The previous checks were conducted on January 27, which means the breaks occurred sometime between Jan.27 and Mar.19. NASA said Tuesday that there were two small breaks in the left middle wheel of the rover. Images taken in early 2016 showed only cracks in the wheels. NASA has been tracking Curiosity’s wheels since 2013. The space agency also routinely conducts ground-based tests to see how much damage the wheels can withstand.

The rover has a total of six wheels, each 16 inches across and 20 inches in diameter. Each wheel has 19 zigzag treads (NASA calls them grousers). The grousers allow Curiosity to balance its nearly 2,000-pound weight while strolling through Mars’ rough and rocky surface. The left middle wheel is missing a few treads, and has dents and holes in it.

Curiosity’s wheel yet to reach 60% of lifespan

Curiosity Project Manager Jim Erickson said in a statement that despite some wear and tear, all the six wheels have enough lifespan left to take the rover to all the planned destinations. NASA will try to reduce further damage to the wheels by avoiding rough routes. It’s worth pointing out that the rover has already completed its primary mission, and has lived twice as long as planned.

Ground-based tests conducted by NASA show that a wheel reaches 60% of its useful life when three of its grousers have broken. Until now, two grousers of the left middle wheel have broken. It is just one break away from reaching 60% of its lifespan. All the other wheels are working just fine, so it shouldn’t be a big deal. Curiosity Project Scientist Ashwin Vasavada said the breaks were an expected part of the life cycle of wheels.

The rover is in Murray formation

Vasavada added that it wouldn’t change NASA’s current science plans or diminish the chances of studying the mineralogy on Mount Sharp. Curiosity is currently in the Murray formation in the Mount Sharp region, which is located in the Gale Crater. It is studying the rock layers for ancient climate records.

According to NASA’s plans, the rover still has to travel at least six kilometers to study the lower rock layers of Mount Sharp.