And dust "storms" might have negative effects.
The last time a spacecraft encountered a global dust storm on the surface of Mars
was in 1971, when the Soviet lander, Mars 3, ran in to quick problems on the surface of Mars due to the storm....failing as a science mission as a result.
Global dust storms on Mars may reduce solar energy reaching the surface of Mars
down to critically low levels; low enough to put the solar batteries on both MER rovers
out of business quick...Hey! If the rovers don't get enough 'juice', their electronics will simply freeze and become inoperative.
As far as I recall, both rovers rely on electric heating elements, instead of radioactive isotopes, to keep their electronics relatively warm.
I hope I'm wrong about the threat of the martian dust storms.