Mars fights back!


Two of the raised treads, called grousers, on the left middle wheel of NASA’s Curiosity Mars rover broke during the first quarter of 2017, including the one seen partially detached at the top of the wheel in this image from the Mars Hand Lens Imager (MAHLI) camera on the rover’s arm.

This image was taken on 19 March 2017, as part of a set used by rover team members to inspect the condition of the rover’s six wheels during the 1,641st Martian day, or sol, of Curiosity’s work on Mars.

Holes and tears in the wheels worsened significantly during 2013 as Curiosity was crossing terrain studded with sharp rocks on the route from near its 2012 landing site to the base of Mount Sharp. Team members have used MAHLI systematically since then to watch for when any of the zig-zag shaped grousers begin to break. The last prior set of wheel-inspection images from before Sol 1641 was taken on 27 January 2017, (Sol 1591) and revealed no broken grousers.

Longevity testing with identical aluminium wheels on Earth indicates that when three grousers on a given wheel have broken, that wheel has reached about 60 percent of its useful life. Curiosity has driven well over 60 percent of the amount needed for reaching all the geological layers planned as the mission’s science destinations, so the start of seeing broken grousers is not expected to affect the mission’s operations.

As with other images from Curiosity’s cameras, all of the wheel-inspection exposures are available in the raw images collections at

Curiosity’s six aluminium wheels are about 50 centimetres in diameter and 40 centimetres wide. Each of the six wheels has its own drive motor, and the four corner wheels also have steering motors.

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