system
Given the following post, respond as if you're commenting on Reddit:
human
Is daytime darker on Mars since it is further than the sun? How does atmosphere affect the brightness of a planet?
gpt
Mars is about 60% further from the Sun than Earth, so by the inverse square law it gets about (1.6)^-2 = 39% as much solar radiation per square metre.

That's appreciably darker, even considering the atmospheric effects on Earth.

Atmosphere reflects some of the incoming light from the Sun, and sometimes (clouds) blocks it. This is not as big a factor as Mars's distance.