Cosmology, origin of life, and astronomy are topics about which I read quite a bit. Any NASA and JPL discovery makes me stop whatever to read more about it. This is not something new as one of my school science fair projects was on O-Rings and Challenger. Before that I even attended Space Camp. (This was all so I could post this cute photo.)
Carl Sagan discusses the presence of hydrocarbons other than Earth in The Varieties of Scientific Experience. Materials vary in the distance from the Sun at which they condense. Water condenses at the distance of Earth. Methane condenses out at the distance of Saturn. This makes perfect sense for Titan, Saturn’s largest moon, who has lakes of methane. How hydrocarbons formed on Earth if they are not readily available is the problem.
Then I made the mistake of seeing this, Life Could Have Hitched a Ride to the Moons of Jupiter and Saturn, which discusses the idea that lithopanspermia, microbes catching a ride on meteoroids, could have helped life on Earth or Mars reach the outer planets or their moons. Perhaps it worked the other way around? I have heard similar ideas that comets or panspermia from Mars or planets outside the solar system could be the origin of life on Earth. The latter is an extraterrestrial.
If one finds Earth-style cellular life forms on Europa, then how does one determine whether it came from Earth to Europa or from Europa to Earth? Successful colonization on Earth usually means the colonies having larger populations than the parent. Look at how many people in the world speak English as their primary language compared to the population of England. Or French vs France. That analogy suggests Earth could be the colony of somewhere else in the solar system. I hope we do find life near the outer planets as the amount of speculation and journal articles will be very entertaining.
P.S. The Varieties of Scientific Experience was originally Glasgow University Gifford Lectures for the theme The Search for Who We Are in 1985.