The dominant religion on my world (created by a race of dragon-like humanoids) believes that their species originates from an ancient being that sacrificed itself to defeat a great evil at the center of the cosmos. Its body remained adrift in space until it was eventually captured by the gravity of the young Earth-like planet that this species calls home. They believe this moment serves as the evolutionary beginning of the species, but also as the foundation of the land itself.

This idea is largely inspired by the panspermia hypothesis of distributing life across the universe, which I'll admit I'm still a bit shaky on the details of. In this case, this ancient being would be the vessel by which the necessary components of life were ferried to the planet, preserved in space within its body until such time that it just so happens to be lucky enough to come across a planet capable of harboring life. We can assume it managed to survive atmospheric entry, and that it crashed into a body of water if that helps the creation of life.

So this is of course a religious idea, but I'm curious to know if such a thing is actually possible:

(1) Could a life form (an utterly massive one, on the scale of a continent) remain adrift and preserved in space until its body collides with a habitable planet, introducing new bacteria/cells/genetic material that had remained dormant?

(2) Could this happen to the extent that some species that evolve from this event take on a similar appearance to the source, adapted by evolution?

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    $\begingroup$ There are plenty of spores that can survive a lot and still be viable. $\endgroup$ – John Feb 3 at 1:52

(1a) Pansermia is possible and arguably likely

What you're looking for is a specific type of panspermia called lithopanspermia - the transportation of organisms embedded in rock between worlds. The benefit of putting organisms inside rock (as opposed to clinging to the outside) is that they can lie dormant for thousands of years, unaffected by radiation. They'll need thousands of years, too. Space is vast, and orbits change slowly. Consider that the ALH84001 meteorite, which was blasted off of Mars, spent 16 million years in space before landing on Earth. Luckily, some bacterial spores may be viable on the order of tens of millions of years, so although panspermia takes a while, it could work.

(1b) ...but it's hard to get such a big organism into space.

A continent-sized animal could not exist without magic. Unless your life form is a tree like Pando or an unreasonably large fungus, it will be crushed under its own weight.

Assuming it does exist, my biggest question for you is: how did the progenitor organism get into space in the first place? A continent's worth of mass can't be lifted without smashing the entire planet apart. Such an impact might fry all bacterial life.

I would suggest only blasting off a part of the organism - or using the "progenitor" as a metaphor for smaller-scale lithopanspermia.

(2) Similarities depend on the size of the life transported.

The creatures on the starting and ending planets will be related only by their latest common ancestor - whichever microorganism is lucky enough to hitch a ride on a meterorite. If that organism happens to be a eukaryotic, multicellular microanimal, then the new life will share physiological similarities with it, at least for the first few million years. If that organism is a simple bacteria, expect only cellular-level similarities.

Fascinatingly, in really close planetary systems like the TRAPPIST-1 system, panspermia could occur in as little as 100 years. On such a short timescale, you could transport some pretty big life on accident.

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    $\begingroup$ For (1b), I've actually asked a similar question to this before! I've been assuming that that this creature has either: (a) always existed within space since the beginning, and so never needed to worry about its weight, and/or (b) is effectively a god, and thus can do things that otherwise violate physical laws. The latter is a bit too handwave-y easy for my tastes as a writer, but it is the idea the religion holds as true and uses as a point of worship. $\endgroup$ – Vigilant Feb 3 at 3:06

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