Yeah, so what did happen to Peter Clayborne? Let's find out.
When the elevator begins to collapse, he and the rest are riding it down. Deciding they aren't in such a hurry to reach the bottom, they put on space suits and bailed; Peter floats through space, the others drifting away from him.
He tries to keep calm, not waste his oxygen on an increased heartbeat.
He falls asleep twice. After the second time, a ship finds him floating with only an hour of air left. Now let's just take a moment to consider how large space truly is and how lucky Peter is that someone stumbled across him. Kind of makes winning Powerball look like a sure thing, right?
The ladies pick him up and listen to his story, then they all head down to Mars, safe and sound.