Hi there! Does anyone here know what the typical light levels are at the Martian surface (in daylight hours!) and how they vary in magnitude through time? I'd prefer a measurement close to the equator, but I'd be happy with one from anywhere at the surface. I can easily calculate the solar irradiance and hence determine the light levels outside the atmosphere, but due to dust loading in the atmosphere that would be an approximation which does not hold at the surface. I am aware that the Mars 3 lander measured light levels of 50 lux (see: http://linkinghub.elsevier.com/retrieve/pii/0019103573901206 [Broken]) at the surface in 1971, and that that was suspected to be during a dust storm. I am also aware that the dust storms of July 2007 "blocked 99 percent of direct sunlight to [Opportunity]" (http://marsrover.nasa.gov/newsroom/pressreleases/20070720a.html [Broken]) but neither of these give me a measure of the typical light intensity/level there on a day-to-day basis in a location with no dust storm activity at that time. Any ideas or measurements/references? Thanks in advance!