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Comment by bmitc | Hacker News Reader

I haven't read about this in a long time, but I have always been curious why the wheels weren't tested more on Earth and designed to be more hardy. Curiosity has apparently only traveled 12.5 miles, and that seems extremely low for such heavy damage. I would have guessed that tests on Earth would have logged many more miles than that, but I should look into their diagnosis of what went wrong.

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The rovers were extensively tested on Earth. However, Mars has lower gravity than Earth, which would of course have an impact on the wear on the wheels. Maybe there was an underestimation when applying the lessons on Earth to Mars gravity?

https://www.planetary.org/articles/08190630-curiosity-wheel-... explains the root cause.

Thanks for that link. I think I have read something similar in the distant past but read through it again.

> There are [places] on Earth that do have these sharp ventifacts, but we hadn't seen them on Mars and we didn't test against them

This is whats so curious. In their testing on Earth after the fact, they found:

> Bedrock with lots of rocks: ~8 kilometers

> Lots of rocks, not on bedrock: 13-14 kilometers

> Bedrock with few rocks (think flagstones): 30-40 kilometers or more

It's just very surprising they didn't think to test on more varied Earth terrains, looking for worst case scenarios, where they would have clearly found this limitation. It is my understanding that the wheel damage became a major limiting factor of Curiosity's mission.

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