[Space] Panspermia and the Campgaign

[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.

[whswhs]

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.

There are lots and lots of plants here on Earth that will kill you, quickly or slowly, if you eat them. In fact there are plants that have evolved chemical compositions specifically to make them toxic to plant-eaters; it's a common passive defense strategy.

Bill Stoddard

[Flyndaran]

Originally Posted by whswhs

There are lots and lots of plants here on Earth that will kill you, quickly or slowly, if you eat them. In fact there are plants that have evolved chemical compositions specifically to make them toxic to plant-eaters; it's a common passive defense strategy.

Bill Stoddard

And humans are pretty darn omnivorous as complex species go. Look at all the things we love that would kill dogs, or cats.
But there is a difference between most things are inedible, and absolutely everything on the planet is.

[thrash]

Originally Posted by 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

Do you have a cite for that? I just finished a graduate level class in meteorites, and ALH84001 has unequivocal Martian isotope ratios, not terrestrial. The 'fossils' are controversial, not the origin.

Panspermia would most likely work on the scale of bacteria and other single-celled organisms, not more complex life. The result would be ecosystems descended from the same progenitors, but not necessarily more closely related than, say, humans and the tube worms that live in black smokers on mid-ocean ridges.

[Anthony]

Originally Posted by thrash

Do you have a cite for that? I just finished a graduate level class in meteorites, and ALH84001 has unequivocal Martian isotope ratios, not terrestrial. The 'fossils' are controversial, not the origin.

I'm sure it didn't go from Earth to Mars and back (there's no real mechanic that would allow rocks to be ejected off of Earth), but you'll get a significant number of meteorites that have been colonized after landing.

[Nereidalbel]

Originally Posted by Anthony

I'm sure it didn't go from Earth to Mars and back (there's no real mechanic that would allow rocks to be ejected off of Earth), but you'll get a significant number of meteorites that have been colonized after landing.

Large impacts have no issue launching rocks at escape velocity. So, yes, the mechanic certainly exists.

[aesir23]

Originally Posted by Anthony

(there's no real mechanic that would allow rocks to be ejected off of Earth).

It's my understanding that there have been several impacts in Earth's history powerful enough to launch rocks into space. The dinosaur killer, for example.

Also large volcanic eruptions like Tambora.

Is that incorrect?

[Anthony]

Originally Posted by aesir23

It's my understanding that there have been several impacts in Earth's history powerful enough to launch rocks into space. The dinosaur killer, for example.

Hm. I may have overestimated the difficulty, it looks like at least some astronomers think it's possible.