Wheel wear a worry for Mars mission

“WANTED: Someone to replace six wheels showing unexpected signs of wear. Must be prepared to travel full 450-million-kilometre round trip to replace them.” NASA has revealed its Mars rover, Curiosity, is in desperate need of a new set of hoops after the aluminium ones fitted to the one-tonne remote control vehicle started showing signs that they may not go the distance.

The rover is only 16 months into its mission to explore the Martian landscape, and has driven only about 4.5 kilometres at a speed of only 2.4 metres every hour as it makes its way over the crater-riddled surface.

However, sharp rocks and the rough Martian surface have taken their toll on the lightweight aluminium wheels, which NASA said had shown accelerated wear over their last month of service.

A self-image taken by the rover shows numerous scratches and dings, and even holes, in the wheels. Engineers will soon program Curiosity to drive to a smooth patch of ground to take a closer look at the wheels using the rover’s on-board camera on the end of its extending arm.

“We want to take a full inventory of the condition of the wheels,” NASA Mars Science Laboratory project manager Jim Erickson said.

“Dents and holes were anticipated, but the amount of wear appears to have accelerated in the past month or so.

“It appears to be correlated with driving over rougher terrain,” he said.

“The wheels can sustain significant damage without impairing the rover's ability to drive. However, we would like to understand the impact that this terrain type has on the wheels, to help with planning future drives."NASA said Curiosity's path had taken it across an area with sharp rocks embedded in the ground.

“Routes to future destinations for the mission may be charted to lessen the amount of travel over such rough terrain, compared to smoother ground nearby,” the space agency said.

The wheels include special cut-outs that spell out the letters “JPL” in morse code – it stands for “Jet Propulsion Laboratories”, the section within NASA that runs the Mars missions.

The morse code allows scientists to check and calculate the real-world travel of the rover in case the on-board numbers are put out by wheelspin.