Even after found the secret room in his base, Sam still cannot face the reality that he is a clone. The memory of his family was his faith and support during the pervious three years. He cannot believe he is a clone and all these are just memory from the original Sam. He has to call home to conform what he found. What him found is devastating to him. After called back home, him found his wife in his memory actually died fifteen years ago, and there is a Sam with his daughter Eva. This becomes the last straw breaks the camel's back. He falls apart immediately and said "That's enough, that's enough. I want go home." But where is his home? At this point, his face becomes pale under the sun light. The soft slow music becomes louder and mixed with his sobbing. The camera shifts out of the rover, moving from the sun to the earth. In his eyes, I guess the blue earth looks just familiar and strange. It is familiar in his dream during the last three years. However, when his dream breaks, it is no longer the home he thought. Every hope on that planet is lost.
This is the most touching moment to me in this movie. I saw the faith of sam is fallen apart, and he lost his courage to live. I guess that's the reason he give up his chance back to earth. At his last moment, he opened his eye, and witnessed the spaceship depart from the moon, with the other Sam in it. Eventually, people on earth knows what happened, and the cycle of cloning on earth could be stopped. I guess this is probably the best ending that can comfort him.