Why do aliens come to earth?

He is talking nonsense. We may have come from Mars where there was water 3.8 billion years ago. But it was destroyed by disaster. The south pole of the earth is 3.8 billion years old. There are fossils of Martian stones with microbial fossils on them. Add aliens to the earth. Did you hear the news? The universe is expanding, and distant galaxies leave us at the speed of light! If there are aliens in distant galaxies, they can't go back!