Curiosity’s most damaged wheel appears to be surviving the rough terrain on Mount Sharp

Curiosity's middle left wheel, from November 2022 to July 2023
For original images go here and here.

In today’s download of images from Curiosity was a set of pictures taken by its Mars Hand Lens Imager (MAHLI) of the rover’s wheels, as part of the science team’s routine inspection procedures after every 500 meters of travel.

The picture to the right shows what I think is the rover’s left middle wheel, its most heavily damaged, comparing what that wheel looks like now versus what it looked like in November 2022. At that time five of the wheel’s zig-zag grouser treads were broken, three of which are visible in both pictures. The numbers indicate identical wheel treads.

As you can see, after more than seven months of travel across some of the roughest and rockiest ground so far seen on Mars, no more grousers have broken in the new picture. The plus (“+”) signs indicate places where I think some additional metal between the grousers appears to have broken away, but even here the additional damage appears minimal.

Based on past wheel inspections, I expect more images will be taken in the next day or so. We shall see if those pictures indicate any further damage elsewhere. Based on this new picture, however, it appears that the care the science team takes in picking Curiosity’s route, as well as its software (designed to avoid the worst terrain), is continuing to preserve the wheels from further significant damage.

Further damage to Curiosity’s wheels

Curiosity wheel comparison of damage
For the original images, click here for the top photo and here and here
for the bottom photo.

The photo comparison to the right, created from high resolution images taken by Curiosity on Mars two months apart, provides us a new update on the state of the rover’s damaged wheels. It shows damage on the same wheel that I have been tracking for several years.

The numbers indicate the same treads, or grousers as termed by the science team. The “+” sign indicates spots where new damage has occurred since the previous photo.

The top photo was taken on June 3, 2022, and was the first to show new damage in more than five years. The bottom photo was taken on August 6, 2022, and shows that another small piece on the same grouser has broken off during the past two months.

Other than this change, however, the rest of the grousers appear unchanged. Moreover, a comparison with an earlier image of this same wheel taken in the summer of 2021 shows that grouser #6 as well as the unnumbered one just below appear also unchanged.

The damage in grouser #5 however is still concerning, and reflects the increasing roughness of the terrain as Curiosity climbs higher and higher on Mount Sharp. Though the science team has been very careful since the rover’s first few years on Mars to travel around obstacles that could damage the wheels, it apparently is becoming harder to do so.

However, even if this wheel eventually loses all the metal between the zig-zag grouser treads, the science team has said it has “proven through ground testing that we can safely drive on the wheel rims if necessary.” The team as also said they do not think that is likely, at least not for a long time, and based on the rate of damage documented by these pictures, this appears very true.

The new damage on Curiosity’s wheels

Comparing a Curiosity wheel from January to June 2022
To see the original images, go here and here.

On June 23, 2022 the Curiosity team provided a major update on the rover’s status on Mars, noting that because of new damage discovered on one of wheels, they were increasing the frequency of their wheel checks from once every 1000 meters of travel to once every 500 meters.

The team discovered that the left middle wheel had damaged one of its grousers, the zig-zagging treads along Curiosity’s wheels. This particular wheel already had four broken grousers, so now five of its 19 grousers are broken.

The previously damaged grousers attracted attention online recently because some of the metal “skin” between them appears to have fallen out of the wheel in the past few months, leaving a gap.

The photo comparison to the right might be showing that specific wheel, or not. The top image was taken January 11, 2022, and when compared then with an image taken six months earlier showed little change. Thus, in January 2022 it seemed the wheels were holding up well as Curiosity traveled into the mountains.

The new image at the bottom, taken June 3, 2022, shows new damage (as indicated by the plus sign) which had occurred sometime in the past six months. During that time the rover had attempted to cross the incredibly rough ground of the Greenheugh Pediment, and had been forced to retreat because the ground was too rough.

This most recent wheel survey in June thus confirms that the decision to retreat was a wise one. It appears that while the rover’s wheels can take the general roughness of the terrain in the foothills of Mount Sharp, the Greenheugh Pediment was beyond the wheels’ capabilities.

Wheel update on Curiosity

Periodically, the Curiosity science team stops from its research to reassess the condition of the rover’s wheels. To do this they use the rover’s color camera, dubbed the Mast Camera (Mastcam), taking close-up pictures of the wheels to compare those with earlier photographs see if there has been any additional damage and deterioration over time.

Yesterday Mastcam took a new series of images of the rover’s wheels. Below are two pictures, the left taken on August 27, 2017, the right taken on July 7, 2019. I have annotated the images to help indicate where they match.
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It seems Curiosity’s wheels are wearing out faster than expected and engineers want to know why.

It seems Curiosity’s wheels are wearing out faster than expected and engineers want to know why.

The increasedwear recently appears to be because the rover was traveling over rougher terrain. Nonetheless, JPL engineers are going to monitor the rover’s travel and wheel damage more closely in order to gauge that wear better for future travel.