The client ask for a cover for the "Red Planet" novel of Robert A. Heinlein, one of the best he wrote for young readers -besides, I am a fan of Heinlein's.
Try to keep a 50's sci-fi look in the lines and reflect the martian landscape and a character named Willis, the bouncer in the visor, like the viewer is the martian. Avoid the familiar desertic martian landscape because in the story Mars is a jungle.