Re: Mars had life, but war broke out
"And the remnants had fled to Earth."
That's close to the plot of 'Inherit the Stars' - the first book of the Giant Series by James P. Hogan. The planet was 'Minerva', located in what is now the Asteroid belt, instead of Mars, and the human survivors got to Earth via the Moon, which originally orbited Minerva.
Not a bad read.