Defense Mech by Ray Bradbury in Planet Stories Spring 1946.
Halloway stared down at Earth, and his brain tore loose and screamed, Man, man, how'd you get in a mess like this, in a rocket a million miles past the moon, shooting for Mars and danger and terror and maybe death.
Notable works:
Fahrenheit 451
The Martian Chronicles
Something Wicked This Way Comes
The Illustrated Man