The Curiosity rover has only driven about three miles after more than a year on Mars, but her thin aluminum wheels already appear to be feeling the pain.
After completing a software upgrade on the one-ton robot last week, officials at NASA's Jet Propulsion Laboratory announced that the next task would be to "check the wear and tear on the rover's wheels."
Bloggers first noticed a small hole in Curiosity's left-front wheel in October, but at the time mission specialists assured the public that dents and holes were anticipated and would not impact the mission.
Here's a photo from Oct. 2, where we've highlighted some of the apparent punctures.
Damage seen in a more recent photo of the same wheel taken on Nov. 30 has raised more concern.
"The amount of wear appears to have accelerated in the past month or so," Mars Science Laboratory project manager Jim Erickson said in a statement.
Based on the photo, some punctures that were visible in October appear to be getting larger, and there are also more of them.
The rover has been driving over rougher terrain than during earlier months of the mission, which is probably responsible for the more obvious holes and scratches, NASA said.
That's why the next activity will be to use the camera at the end of the rover's arm to get a closer picture of the damaged tire.
"We want to take a full inventory of the condition of the wheels," Erickson 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."
Curiosity's wheels are constructed from tough aluminum, with some regions only .75 mm thick (.03 inches). But that's still about six times thicker than the aluminum walls of a soda can, for instance.
The wheels were purposely designed to be thin and light to reduce weight and cost.
The wheels are 20 inches in diameter, making them larger than the wheels of car. The wheels have "cleats" (like the shoes of a soccer player) that are designed to keep the rover from slipping as it drives over rocks and climbs steep hills.
Curiosity still has a five-mile journey across the Gale Crater landing site before she reaches Mt. Sharp. If the wear and tear on the wheels is really getting worse, the rover's managers said they may have to change the route to avoid sharp rocks and other rough terrain that would further damage them.
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