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Comment by noobermin | Hacker News Reader

One of the callers (a biologist, so not a crackpot) on TV suggested that given how close the planets were, he wondered if it were possible for there to be cross contamination between the planets given how close they are to each other. He referred to them being part of the same "ecosystem." I'm not sure how feasible that is as a non-astrobiologist, but it is an interesting idea.

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Very likely, since this happens between Mars and Earth:

https://en.wikipedia.org/wiki/Martian_meteorite

Fascinating! Would vira or bacteria beable to survive travelling from Earth to Mars in or on a rock or vice versa?

Possible, but cross-section for collision is way way smaller in the Earth-Mars system. Cross-section goes as r^-2 so the closer the bodies, the 'way better' it is.

Short answer: almost certainly yes, although i presume this is an improbable event.

It's not that improbable. They've found meteorites on Earth that have been identified as having come from Mars based on their mineral contents.

Sure, I was referring to the part where the microbe survives the initial blast, the passage through space, reentry, and landing, and happens to land in a spot where it can survive.

According to some research, microbes survival in meteorites is very likely (if they exist)

https://www.ncbi.nlm.nih.gov/m/pubmed/11543506/

I know enough biology to be skeptical of papers like that (although, I admit I was skeptical when papers from the 50s predicted interplanetary mass transport, and didn't change my mind until we found Martian meteorites). I'd like to see actual evidence of this.

I actually think the rock getting into space with the microbe embedded in it is not that unlikely (many rocks in the earth are laced with bacteria), nor the space transport. I think the excessive heat of rentry, the force of impact, and the difference in target ecosystems are what are going to kill the microbes.

Tardigrades do survive in space: https://en.wikipedia.org/wiki/Tardigrade

IIRC, that is a serious hypothesis for how life began on earth, seeded from elsewhere (maybe not Mars).

But certainly someone here knows more than I do about it ...

The theory is called Panspermia

https://en.wikipedia.org/wiki/Panspermia

Roughly quoting Neal de Grasse Tyson: Since so many bacteria survive outer space there is a good chance it's because of - yes - survivor bias. If only because early earth was bombarded so often that fragments of the planet with microbes took of in a meteor strike and returned home after a while in space.

Considering the time scales involved, it wouldn't surprise me if multiple planets around nearby stars happened to be seeded with earth based bacterial/archaea life.

One of the presenters is an old friend from college. Folks were offering him money to mention "Zod, our Galactic Overlord" on the air. I guess that didn't happen?

No unfortunately, I don't think they did. That would have been hilarious.

The survivability of several organisms has been actually tested https://en.wikipedia.org/wiki/List_of_microorganisms_tested_...

There has been and continues to be cross-contamination between Venus, Earth, and Mars, so it seems likely that planets much closer together, and passing each other more frequently would have more 'communication' of materials.

Continues to be...? Outside of human action, what's the vector?

My understanding is that it is mostly due to solar wind, meteorite impacts, and various other infrequent events.

powerful meteor strikes spreading debris out of orbit.

And the debris isn't heated enough to be sterilized.

https://en.wikipedia.org/wiki/Martian_meteorite

Gene Wolfe mined this idea for some of his science fiction works, except it was alien life making the jump ... Fifth Head of Cerberus & Blue's Waters/Green's Jungles.

Even if bacterial material were being transferred all the time, I think it'd be a stretch to call them the same "ecosystem" unless they were actually reliant on each other. But I'm not an biologist either.

https://en.wikipedia.org/wiki/Panspermia

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