[Space] Panspermia and the Campgaign

[scc]

I'm pretty sure that there was a rock found from Mars that showed signs of carrying bacteria, that turned out to have come from Earth to begin with (The rock went from Earth, to Mars and then back again) so it's possible

[Nereidalbel]

Planets being habitable is not explained be panspermia; that's just being the right distance from the parent star. As for being able to eat plants on other worlds, that's just luck. Billions of years of evolution are more than enough to create large differences, as well as planets having differing chemical compositions.

[scc]

It being in the right temperature zone means the planet has the POTENIAL to support life. It also has to be big enough to retain the right elements and an atmosphere. Once those criteria are meet an interesting paradox arises, life begets life, in basic terms you need the first beginnings of life to kickstart the entire thing to higher and higher levels. In simple terms if you kill off all the trees on Earth, it will soon be life less

[Genesis]

Originally Posted by Nereidalbel

Planets being habitable is not explained be panspermia; that's just being the right distance from the parent star. As for being able to eat plants on other worlds, that's just luck. Billions of years of evolution are more than enough to create large differences, as well as planets having differing chemical compositions.

It's worth noting that most of the things on this planet aren't edible. Of course, that's partly the result of a billion-year arms race between things that like to eat and things that'd rather not be eaten.

I think panspermia is a perfectly fine explanation for having compatible biochemistries on neighboring planets, in a "soft" sci-fi game. As a rigorous theory it has numerous problems, but so what? Rule of Cool it for maximum campaign enjoyment.

If you want to make it a little more rigorous, you can always opt for "Ancient Astronauts" notions - an ancient civilization developed space travel, seeded the system, then collapsed (for whatever reason... space plague? Gamma ray burst? whatever). Leaving the descendants of the organisms they brought with them on all the worlds they visited. Some places look just like the earth-analogue, some look quite different. You can posit intelligent life, closely related to humans (as the descendants of old colonists, sent back to the stone age and unable to bootstrap themselves up to UT without fossil fuels left by past epochs that didn't happen on non-earth-analogue planets), or not. It's your game!

A more serious answer to your questions: Unless they're evolved for it, you're not going to get terrestrial seeds clinging to meteorites. On the other hand, what's to stop the whole system from being seeded by some exterior source specifically evolved for interstellar distribution? Lots of fiction has space-based organisms, or organisms with a partly space-based life cycle. Something like this: a great interstellar tree approaches the main star of the system eons ago, but is shattered by a rogue planetoid. Pieces of its destroyed body, with all the attendant microorganisms, parasites, and symbiotes that usually ride with it, fall to ground on most of the planets in the system. The great tree is gone, but conditions on the proto-worlds are similar enough to the host for some fraction of attendant life to survive. Everything gets seeded at the same time, all the biochemistry is roughly similar, and when intelligent life evolves on of the planets it finds that its neighboring worlds are strangely (or not-so-strangely, probably, from their perspective) hospitable.

As for the sentience problem, it's only as much of an issue as you want to make it. As another poster mentioned, we've been on this planet for several billion years (for a loose definition of "we") and only one technological species has evolved in all that time. So hey, if you don't want there to be sentient species on the other planets, there aren't. If you do, then there are. it's your game, and either is just as reasonable as panspermia in the first place.

[jeff_wilson]

Originally Posted by Nereidalbel

Planets being habitable is not explained be panspermia; that's just being the right distance from the parent star.

That's not the whole story; pre-life Earth did not have a breathable atmosphere or surface water and you can see how Venus has a similar distance from the sun but a very different condition from earth's current one.

[Nereidalbel]

Originally Posted by jeff_wilson

That's not the whole story; pre-life Earth did not have a breathable atmosphere or surface water and you can see how Venus has a similar distance from the sun but a very different condition from earth's current one.

Breathable to us? No. For anoxic life? It was perfect!

[Flyndaran]

Originally Posted by Nereidalbel

Breathable to us? No. For anoxic life? It was perfect!

I've been playing with creating an alien anaerobic methanogenic PC species. Oxygen is powerful stuff, but looking around extant life, I found ways to increase their efficiency to just barely equal ectothermic animal life.
A very hot bright planet and daytime photosynthesis makes them quite competitive.

[Flyndaran]

Originally Posted by jeff_wilson

That's not the whole story; pre-life Earth did not have a breathable atmosphere or surface water and you can see how Venus has a similar distance from the sun but a very different condition from earth's current one.

We owe our present concept of life to the great oxygen event. But I'm not sure it was necessary to prevent a runaway greenhouse event at Earth distances.
I thought surface water coalesced very early, but that it's hard to absolutely prove without known hydrates and oxides from later in the geological record. Blasted tectonics messing up the data. ;)

[scc]

Originally Posted by jeff_wilson

That's not the whole story; pre-life Earth did not have a breathable atmosphere or surface water and you can see how Venus has a similar distance from the sun but a very different condition from earth's current one.

Right, other then the planet life evolved on I've got half a dozen planets like this, if I can just transport some of the that made the first planet habitable to the others, everything's good.

And the meteorite I mentioned from Earth to Mars and back again was on the news several years back

[jeff_wilson]

Originally Posted by scc

Right, other then the planet life evolved on I've got half a dozen planets like this, if I can just transport some of the that made the first planet habitable to the others, everything's good.

And the meteorite I mentioned from Earth to Mars and back again was on the news several years back

Yes, but it was a different one than the one with supposed microbe fossils, and may have been discredited if a current grad student can't locate a reference.