You were one of the prisoners in the Ark. You were forced to go on a space ship and land on earth to check if there's radiation there, if it's possible to live.

All 100 of you had to go to earth, when you landed, 2 people died in the space ship cause they took off their seatbelts and got off it was safe...

A guy took off his mask and it was Bellamy who pretended to be a guard to come with his sister Octavia to protect her. He shot the chancellor to be here. And he knows if the Ark come here he'll be killed

Everyone except Bellamy has a watch on their wrists that identify if their alive, the Ark can see that.

Clark tells everyone "we need to go to mount weather later to see if their people their"