In his weekly homily on Monday, the Pope explored the idea that extraterrestrial beings might want to join the Catholic church and determines that they should be accepted with open arms.
From the Vatican:
"That was unthinkable. If – for example - tomorrow an expedition of Martians came, and some of them came to us, here... Martians, right? Green, with that long nose and big ears, just like children paint them... And one says, 'But I want to be baptized!' What would happen?"
"When the Lord shows us the way, who are we to say, 'No, Lord, it is not prudent! No, lets do it this way'... and Peter in that first diocese - the first diocese was Antioch - makes this decision: ‘Who am I to admit impediments?' A nice word for bishops, for priests and for Christians. Who are we to close doors? In the early Church, even today, there is the ministry of the ostiary [usher]. And what did the ostiary do? He opened the door, received the people, allowed them to pass. But it was never the ministry of the closed door, never."