The aluminum wheels on NASA’s Curiosity Mars rover are showing signs of wear and tear as the rover continues its exploration of the Red Planet.
Two small breaks were discovered on the rover’s left middle wheel in the raised treads, called grousers. Testing showed that at the point when three grousers on a wheel have broken, that wheel has reached about 60 percent of its useful life. Curiosity already has driven well over that fraction of the total distance needed for reaching the key regions of scientific interest on Mars' Mount Sharp.
Each of Curiosity's six wheels is about 20 inches (50 centimeters) in diameter and 16 inches (40 centimeters) wide, milled out of solid aluminum. The wheels contact ground with a skin that's about half as thick as a U.S. dime, except at thicker treads. The grousers are 19 zigzag-shaped treads that extend about a quarter inch (three-fourths of a centimeter) outward from the skin of each wheel. The grousers bear much of the rover's weight and provide most of the traction and ability to traverse over uneven terrain.
"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."
The monitoring of wheel damage on Curiosity, plus a program of wheel-longevity testing on Earth, was initiated after dents and holes in the wheels were seen to be accumulating faster than anticipated in 2013.
Through March 20, 2017, Curiosity has driven 9.9 miles (16.0 kilometers) since the mission's August 2012 landing on Mars. For the past four years, rover drive planners have used enhanced methods of mapping potentially hazardous terrains to reduce the pace of damage from sharp, embedded rocks along the rover's route.
Image credit: NASA/JPL-Caltech/MSSS