I remember watching Spirit and Opportunity land on mars, sitting next to my uncle,the day he was diagnosed with lung cancer, and I still remember the prediction that the rovers would die in 3 months due to buildup of dust. I couldn't help but wonder that my uncle was, at least, going to outlive them. I was wrong.
"NASA engineers were counting on it to function for just three months" and it is still functioning 8 years later? What an impressive accomplishment.
If I recall, they assumed the solar panels would end up fully covered in dust after 3 months, but the wind just keeps clearing them off.
.00037 mph = 0.0065 inches/sec = 0.165 mm/sec
I don't see Mars-rover races being a spectator sport any time soon. That must require a lot of patience - not sure I care to have that much.
The three year average might be low, but the average speed of the Opportunity rover over the past eight years is over 2700 mph.