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> Could you ground that assumption in some physical reasoning? Microbes are incredibly resilient and adaptive in general. If microbes on Mars are DNA based, the

> Could you ground that assumption in some physical reasoning? Microbes are incredibly resilient and adaptive in general. If microbes on Mars are DNA based, then contact with Earth microbes would be inherently meaningful. I don't think I need to. True, if martian microbes are DNA based then that obviously increases the chance of cross contamination/interaction. But we don't know that any life we find outside of Earth will be DNA based at all. We look for signs of DNA based life, and environments that are conducive to DNA based life because that's the only life we know how to look for. It's the only real life we know. But it is not outside the realm of possibility that the first extraterrestrial life we find, whether orbiting Alpha Centauri or on Mars, isn't DNA based. Personally, I think it's pretty closed minded and Earth-centric to define life (complex or microbial) in that manner.

marshall007 10y ago
I think this would be more accurately framed as a chemistry question. Without knowing the underlying chemistry of extraterrestrial organisms, we can't really make meaningful statements about how they might interact with DNA based life. You can certainly imagine simple, yet highly adapted, microorganisms evolving in the Martian environment where competition is scarce. In this situation, our quite robust terrestrial organisms might overwhelm native populations simply because they are much more adaptable to change and competition with foreign bodies. This still doesn't even touch on the compatibility of the biochemistry. Perhaps life from either origin attempting to consume one another causes volatile chemical reactions, destroying one or both organisms. In this scenario it would come down to which (if any) evolves the necessary chemistry to consume and/or avoid the competition first. More broadly, the introduction of any foreign chemistry at all could be destructive to native populations, let alone the introduction of new life forms. Given the complexities involved and lack of data, I wouldn't feel comfortable making a case one way or the other.

marshall007 10y ago

I think this would be more accurately framed as a chemistry question. Without knowing the underlying chemistry of extraterrestrial organisms, we can't really make meaningful statements about how they might interact with DNA based life. You can certainly imagine simple, yet highly adapted, microorganisms evolving in the Martian environment where competition is scarce. In this situation, our quite robust terrestrial organisms might overwhelm native populations simply because they are much more adaptable to change and competition with foreign bodies. This still doesn't even touch on the compatibility of the biochemistry. Perhaps life from either origin attempting to consume one another causes volatile chemical reactions, destroying one or both organisms. In this scenario it would come down to which (if any) evolves the necessary chemistry to consume and/or avoid the competition first. More broadly, the introduction of any foreign chemistry at all could be destructive to native populations, let alone the introduction of new life forms. Given the complexities involved and lack of data, I wouldn't feel comfortable making a case one way or the other.