"On Mars" means alive for at least 1 Earth day after first being within 100 m of the Martian surface. If there are multiple people of different nationalities aboard a single vessel, as long as at least one of them is American (even if they are oriented at the top of the spacecraft, farthest from the surface at the instant they're within 100 meters) I will resolve this as "yes" if they are alive after one day. This does NOT mean first to take a step on Mars.