0% chance any intelligent aliens have come to visit. There is a non-0% chance that there have been some microbes on an asteroid. There are some variations on the panspermia theory that suggest that life didn’t even originate in this star system. There’s no evidence for any of it of course but it’s possible.
This is an important distinction.
100% chance there is extraterrestrial life out there somewhere
0% chance any of it has come to visit
0% chance any intelligent aliens have come to visit. There is a non-0% chance that there have been some microbes on an asteroid. There are some variations on the panspermia theory that suggest that life didn’t even originate in this star system. There’s no evidence for any of it of course but it’s possible.