91Èȱ¬

Mars is known for its rocky landscape, and it seems that even expert equipment can't escape the planet's rough environment.

Nasa has released a selfie that its Curiosity rover took, showing a huge hole in one of its wheels.

The robot has been exploring the red planet for more than ten years, making plenty of discoveries along the way.

However, the US Space Agency says there's no need to worry as the rover is made of tough stuff, and scientists expect it to carry on with its mission as normal.

Curiosity landed on Mars on 6 August 2012.

The rover has been exploring the surface of Mars ever since, and has made some pretty cool discoveries - even taking the first selfie on Mars!

The robot's mission is to search for evidence of life and to learn more about the planet.

It can take pictures, collect samples and study the surface of the planet - and then beam the information back to scientists on Earth.

According to Nasa, Curiosity's six aluminium wheels were specially designed so that the rover could move across Mars' loose sand, rocks and flat bedrock.

The pictures of the wheel were taken last month by a camera attached to Curiosity's robotic arm.

It's not the first time that a hole has appeared on one of Curiosity's six wheels - in fact cracks have been appearing for years.

Nasa rovers often take detailed selfies of themselves so that a huge team of engineers back on Earth can check them over and make sure they're ok.

They note down each and every crack and then, in order to minimise damage to the wheels, experts keep an eye out for dangerous spots on the planet for the rover to avoid.

They can also adjust the speed at which Curiosity moves across the terrain and slow the robot down if needed.