According to reports; winds seldom obtain 300 mph on Mars. However, since the Mars atmosphere is less than 1% that of earth, comprised of mostly CO2, you must divide your wind speed by at least a factor of 10 in order to get an equivalent wind speed on Earth, so if there is a 100 mph wind it will become like a 10 mph wind on earth. However, because there's absolutely no measurable moisture in that Mars atmosphere, thereby even lesser density is where a 15:1 ratio might actually become more correct, thus 150 Mars mph = 10 Earth mph and, a 100 mph wind would likely resemble 6.7 mph on Earth. In other words, you could easily stand up and walk into and about a 750 mph wind tunnel and, aerodynamic landing speeds would likely require 2000 mph as well as fatter aerodynamic wings spanning nearly a quarter mile across.