Re: How bright is high-noon on Mars as compared to the same time on Earth?

According to Jim Murphy of the Mars Pathfinder ASI/MET Science Team the brightness on Mars is about half the brightness on Earth. Most of this comes from the longer distance: the brightness of an object decreases by the square of the distance of an object from the parent Star. Mars is 150% farther from the sun than earth which would make it about half as bright as eathlight. Then he takes into account the lighter atmosphere and the scattering of light by Mars' red dust and finally arrives at a a value of 44% the brightness of earth or slightly less than half. Further, the sun would have a size in the sky of a typical flashlight beam, rather than 1/2 a degree as on earth. Do a search on Pathfinder and Viking landing site photos and you will get a good idea of the scene on Mars in daylight.

This past year was particularly disappointing to astronomers due to a dust storm coming up of more enormous proportions than usual and obscuring the closest Martian approach to earth in thousands of years. Features which were hoped to be seen by many a backyard astronomer like myself were obscured, and we were certainly disappointed as a result.

http://quest.arc.nasa.gov/mars/ask/atmosphere/Brightness_of_daylight_on_Mars.txt