The funny part is that Science has no explanation for the first living thing coming into existence. So far, only religion has an explanation - and it’s not a scientific one. Up to this point, the origin of life seems to be outside science’s swim lane.
i.e. One of our other planets could be almost identical to earth, yet have zero life on it, because science has no theory on how that could come about. They only have wild hypotheses.
Exactly. We know what conditions are necessary for existing Earth life to survive. We also know that hydrocarbons and complex organic molecules exist elsewhere in our solar system and in other solar systems, and how those are created in the absence of life.
All you need to do to create hydrocarbons and complex organic compounds is put hydrogen, carbon dioxide and some other basic elements under extreme pressure in a contained system with an energy source, stir it for a few hundred million or billion years, and eventually you get hydrocarbons and complex organic molecules. The lower atmosphere of a gas giant (such as Jupiter and Saturn), inside a newly formed and still molten but slowly cooling rocky planet (live Venus or Mars a couple of billion years ago), or deep in the crust or in the upper mantle of a rocky planet that still has a molten core (like Earth) are all perfect environments for creating hydrocarbons and complex organic molecules from scratch over millions of years.
We have no idea, however, how you make the leap from the most complex organic molecule to even the simplest living organism. If you reject the possibility that life was created by a higher power, then the only scientific explanation is to speculate that if you keep stirring complex organic molecules (under pressure and with an energy source), eventually some of them will combine into a simple self-replicating microbe, then somehow evolve into a single celled organism, then somehow evolve into a multi-celled organism.
Unless and until we actually find life somewhere else we have no idea if there is life anywhere else and can only speculate based on the vastness of space.