"but they're pointing out that it does show that forms of life different from our current definitions can exist"

Yes, but not meaningfully different from previous definitions. If this is simply an evolution of existing earth life, then it's just another in a long list of things that we were surprised evolved from conventional Earth life, but is, nevertheless, conventional Earth life. It's more indicative of a slight flaw in our definitions, not time for a radical reexamination of our assessment of the universe.

As I commented in a previous message, people have a history of getting far more excited about this sort of thing than they have scientific justification for. This sure looks like another one of those.

Now, if they could establish that this has to be the actual entirely new branch of life that can be provably not traced back to the same Earth ancestor as everything else, that would be a groundshaking discovery.

Those of us pondering the Great Questions were already not assuming that everything has to look exactly like known Earth life to work. There are numerous obvious different, incompatible mechanism that could exist (different RNA transcription tables, the other chirality for proteins) and an unknown and presumably vastly larger number of unobvious different mechanisms even just for basically Earth life before we really go out into new territory. We've already speculated endlessly about silicon life, ammonia life, mechanisms other than photosynthesis, etc. Don't get me wrong, this is legitimately interesting, and would on its own be worthy of HN, but I have to say the implications for the Great Questions are basically zip. Announcing proof that life can only exist in precisely Earthlike conditions with incredibly tight tolerances would be the surprise.

i think that it is meaningfully different from previous definitions.

perhaps all sparks of life would require the same stuff that it did on earth, that is unclear. but it shows that the continuation of life doesn't necessarily require that same stuff. it means that in searching for life, you don't necessarily have to limit it to the proverbial class M planets.

But how is that a change? We already knew that to the point that we're looking at non-Earthlike planets. We're already looking for life on Titan and Europa, already looking on Mars to see if it had life. We're already talking about life on that tidally-locked mega-Earth that came up a couple of months ago, with otherwise-respectable scientists saying it's 100% likely [1]. We're already not convinced that life has to start exactly as Earth does.

If it's "different", what's the actual difference? What actually changed?

[1]: http://www.space.com/scienceastronomy/earth-like-exoplanet-p...

no. we already theorized that, we didn't know. we didn't have proof. now we do; now we know. the actual tangible differences are likely going to be in funding, research direction, and scope of effort on the topic. who knows what future research will generate off of this?

no, the world hasn't changed. sorry. not yet, at least. but its kind of like watching the moon landing in '69 and scoffing at it because you knew it was coming, you've been reading about NASA working on it for years in the paper.

You're badly misunderstanding my point. I'm not saying this isn't interesting. I'm saying this isn't actually all that interesting when it comes to the Great Questions. It doesn't significantly expand where we already thought life could be. It has not yet established that it is anything other than another evolution of Earth life, which would be a big deal, and from the sounds of it that's still what it is, an adaptation.

This isn't some amazing announcement with profoundly unsettling implications for life in the Universe. It's another in a long series of announcements about how our understanding was limited about how far Earth life could travel. It's roughly similar to how we found non-photosynthetic life around the ocean vents [1], or the recent discoveries of strange life several miles underground [2], or the sky bacteria [3]. I think quite a few people here are not understanding just how many similar discoveries have already been made, we moved on from "all life in the universe will look just like the standard sun-powered ecosystem we live in" quite a while ago.

I guess you could say to the extent this is amazing, we've already been amazed this way. It's cool, but it's a discovery that fits quite comfortably with a number of other interesting discoveries. We're not going to be talking about this in another year. (Except possibly because once people start looking for more examples of this sort of thing I'd lay money they find them.)

[1]: http://en.wikipedia.org/wiki/Hydrothermal_vent#Biological_co...

[2]: http://www.livescience.com/animals/061019_otherworldly_bacte...

[3]: http://www.wired.com/science/planetearth/news/2008/02/bacter...

I'm not a biologist but:

Assuming that arsenic life just adapted, we don't know if it is possible that arsenic life can evolve in a non-earthlike environment or not, do we?

I.e. we don't know if life can evolve in a non-earthlike environment.

Well, no. To know that we'd have to find it to act as proof. What this finding does is expand the bounds of the environments in which searching for life is viable. In other words, we can now consider other temperature ranges and chemical soups and compare them against a new baseline for viability.