Spaceflight Insider

Wheel treads break on Curiosity rover

Curiosity's wheel treads

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. (Click for full, raw image) Caption and Photo Credit: NASA/JPL-Caltech/MSSS

At nearly five years old, NASA’s Curiosity Mars rover (MSL) is starting to show signs of its age following a routine inspection of the rover’s six wheels that revealed two small breaks in the treads on the middle left wheel. The tread breaks were anticipated after longevity tests to similar wheels on Earth showed that tread breaks were likely to occur as the rover ages. The damaged treads, also called grousers, appeared in images taken on March 19 and likely formed since the last tread check on January 27.

Mission status report


A close-up image (taken on Sol 1641) of the broken grousers on Curiosity’s left-middle wheel

A close-up image, taken on Sol 1641, of the broken grousers (indicated by red arrows) on Curiosity’s left-middle wheel. Credit: NASA/JPL-Caltech/MSSS

Routine monitoring of wheel damage on Curiosity began in 2013 after dents and holes began appearing on the wheels at a faster rate than originally anticipated. Tests have been performed to similar wheels on Earth so engineers could get a better sense of the implications for different types of damage to the wheel.

Once three of the grousers have broken on a given wheel, that is an indication that the wheel has reached about 60 percent of its useful life. While the two grousers have broken on left middle wheel represent the only grousers broken to date on the rover, Curiosity has already driven well over the fraction of the total distance to reach key regions of scientific interest as it climbs Mount Sharp relative to the useful life of the wheels.

“All six wheels have more than enough working lifespan remaining to get the vehicle to all destinations planned for the mission,” said Curiosity Project Manager Jim Erickson at NASA’s Jet Propulsion Laboratory, Pasadena, California. “While not unexpected, this damage is the first sign that the left middle wheel is nearing a wheel-wear milestone.”

As of March 20, Curiosity had driven 9.9 miles (16.0 kilometers) since landing on Mars in August 2012. The rover is currently passing through sand dunes as it examines the Murray formation. Its ultimate goal is to reach clay and sulfate-containing geological units further up the slope of Mount Sharp, which could yield further insights into the history of water on Mars. To reach the sulfate unit will require an additional 3.7 miles (6 kilometers) of driving.

Speaking of the potential impacts that the wheel damage could have on rover’s progress to additional science targets, Project Scientist Ashwin Vasavada of JPL said: “This is an expected part of the life cycle of the wheels and at this point does not change our current science plans or diminish our chances of studying key transitions in mineralogy higher on Mount Sharp.”

Curiosity’s six wheels are milled out of solid aluminum, and each of them measures about 20 inches (50 centimeters) in diameter and 16 inches (40 centimeters) wide. The grousers are 19 zigzag-shaped treads that extend approximately 0.25 inches (0.75 centimeters) out from the skin of each wheel. In addition to providing the rover additional traction, they bear much of the rover’s weight.

This is not the first time that a Mars rover has experienced issues with its wheels. The Mars Exploration Rover Spirit suffered a wheel motor failure during its mission that required mission planners to develop strategies to allow the rover to continue navigating across the surface to reach targets of scientific interest.

 

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Paul is currently a graduate student in Space and Planetary Sciences at the University of Akransas in Fayetteville. He grew up in the Kansas City area and developed an interest in space at a young age at the start of the twin Mars Exploration Rover missions in 2003. He began his studies in aerospace engineering before switching over to geology at Wichita State University where he earned a Bachelor of Science in 2013. After working as an environmental geologist for a civil engineering firm, he began his graduate studies in 2016 and is actively working towards a PhD that will focus on the surficial processes of Mars. He also participated in a 2-week simluation at The Mars Society's Mars Desert Research Station in 2014 and remains involved in analogue mission studies today. Paul has been interested in science outreach and communication over the years which in the past included maintaining a personal blog on space exploration from high school through his undergraduate career and in recent years he has given talks at schools and other organizations over the topics of geology and space. He is excited to bring his experience as a geologist and scientist to the Spaceflight Insider team writing primarily on space science topics.

Reader Comments

Perhaps titanium would have been a better choice of material for a component such as wheel treads. I hope the 2020 rover wheels have been redesigned accordingly, without those JPL vanity cutouts.

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