Panspermia

Naturalistic evolutionists often ask, what is the origin of life on Earth?

One theory is panspermia. This is the idea that life on Earth may have originated off-planet, and found a way to Earth. Perhaps "life" (e.g. microorganisms, molecules) hitched a ride from an asteroid that crash landed on Earth, where it found an environment in which it could replicate.

But how likely are microorganisms or molecules to survive a ride in space on an asteroid or the like all the way to Earth? Seems mighty unlikely to me. Isn't there still significant controversy over whether the meteorite dubbed "ALH 84001" may have contained "extraterrestrial life" (in the form of fossilized bacteria)?

However, even if life on Earth originated from a Martian meteorite, which originated from Mars, this only pushes the question back a step. Where did life on Mars originate?

Is the naturalistic evolutionist going to say another planet or moon or other celestial object? In our solar system? Outside our solar system?

If so, then this too pushes the question back a step. And the further steps we have to go back, the worse the probabilities would seem to become, no?

Particularly if all these steps are like ALH 84001 - a random happenstance. What are the chances that a Martian meteorite carrying life would land on Earth to produce life? If the bacteria from Mars originated on a different planet, then what are the chances it would have crashed on Mars? And so on and so forth until the odds would seem to be ridiculously absurd.

Perhaps one way the naturalistic evolutionist could improve the odds is by postulating directed panspermia. That is, intelligent aliens with the capacity for interstellar travel intentionally seeded various solar systems or planets with life. This is a staple of scifi films and literature. Take the most recent Aliens flick, Prometheus, for example.

However, I'm not sure how this improves probabilities either, for then we could likewise ask, from whence did these intelligent aliens with the ability to seed our planet with life come?

Another option is something like self-replicating molecules. If so, how is this essentially different to spontaneous generation, like flies emerging from spoiled foods?

Is it different because these molecules can "self-organize"? In that case, at a minimum, the right conditions for life to self-organize need to be met. This includes not only environmental conditions, but also the operation of specific physical, biochemical, and other forces. Moreover, what keeps "life" self-organized? Are we slipping into some variant of vitalism? And, again, probabilities?

Not sure there's a whole lot left to explain the origin of life on Earth. Certainly not "Godditit"!