This answer to How are the Mars Rovers maintained? reminds us that
...much to the surprise of the early Mars scientists and rover teams, Mars takes care of the dust problem for us! Mars' typical weather generates these dust devils that whip through periodically and clean off the solar panels, thus giving new life to the rovers every time.
Question: How often have dust devil events made a significant improvement in a Martian lander or rover's ability to operate?
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