Can’t comment on our galaxy, per se, but if even a fraction of a percent of the thousands of unexplained UFO sighting are valid, then extraterrestrial life is a certainty regardless of any probability statistics! https://medium.com/@sebeller/i-would-take-a-different-view-and-ask-how-many-credible-ufo-sightings-have-there-been-cc36aed0b272