Is there extraterrestrial life in our solar system?
I say I bet because it's my best guess. It seems at least ever so slightly more likely than not to me. I of course can't say I know either way and I at least hesitate to say I believe as opposed to just I bet because as of yet there is no direct evidence that life exists or not. We don't have information to make a valid induction. Every planet on which we know whether or not life developed has developed life, but that is only 1 planet: Earth. That's the weakest induction ever, but that alone might be enough to guess that non-terrestrial life exists (or has left proof of previous existence) on one of the other 7 planets (not counting Earth), 5 dwarf planets, or 176 moons. Some notable candidates include Mars, Europa, Titan, Enceladus and Venus. There is also some indirect evidence of extraterrestrial life on Mars for instance:
- Trace amounts of methane in the atmosphere of Mars
- gas emissions from heated Martian soil that some argue are consistent with the presence of microbes
- structures resembling nanobacteria were reportedly discovered in an allegedly Martian meteorite, ALH84001
Indeed, a survey of participants at one meeting regarding Martian life indicated that 75 percent of the researchers present agreed that bacteria once lived on Mars and roughly 25 percent agreed that bacteria inhabit the planet now (source). And that's just on Mars! In other places in the solar system, such as Europa, we have hopes of not only finding life but of life with animal-like mobility and intelligence.
I do think we can rule out the possibility of discovering extraterrestrial life with human-like intelligence or human-level civilization to a greater degree than what we can already find in non-human animals on Earth.
What would it mean?
Let's say as I predict that we do find extraterrestrial life in the solar system, either microbial or with animal-like mobility or intelligence. What effect would this have in the minds of the general public? What might mean in terms of what we believe cosmologically?
Considering how vast the galaxy is and how insanely vast the universe is, if we find the life sprung up even just twice in our little corner that is this solar system, I think that would indicate that there is a huge amount of life in the universe. Right now, in terms of life in other star systems, our thinking seems to be that it is most likely to exist on very Earth-like planets because maybe it can only exist on those. But if we find it twice in our own solar system, then that would seem to not merely expand the potential habitable planets by 2 but way more because it would seem life is a lot restricted in terms of where it can develop. The proposition of 2 anomalies in such close range is incredibly harder to dismiss than one. If microbial life or animal-like life is so incredibly common in the universe, which I think is reasonable to conclude if it sprung up twice in the only solar system of which we can find out, then I also think that make it reasonable to conclude there is also lots life with human-like intelligence, technology or civilization. In fact, if we find even microbial extraterrestrial life in our solar system, then I think it's a fair bet to say there billions of other civilizations in the visible universe with human-like intelligence. It also seems to me like a fair bet that some of those civilizations have made contact and communicated with each other or mutually interacted in some way, which is amazing to think about in my opinion. I think it changes the foundation of how we view the universe to so confidently think of it as containing so much life.
I think it would have a lot more of these universal implications if the life found in our solar system, if it's found, comes with evidence that it wasn't the result of previous cross-contamination of some sort but rather originally evolved independently. This is particularly the case with microbial life.
What do you think?