QUESTION: 
Since Mars has a thinner atmosphere than Earth, will it get more 
solar energy than Earth (even though Mars is farther from the sun than 
Earth is)?

ANSWER from Cathy Davis on January 22, 1997:
The atmosphere of Earth does not reduce the amount of solar energy 
that reaches the surface all that much. So there is not a real benefit 
to the thin atmosphere of Mars, except that it will not have cloudy days 
like on Earth!