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Comment by ryandvm | Hacker News Reader

Neat. Though we already know that life works its way into just about every nook and cranny on Earth, so this isn't particularly amazing.

The problem that I see is not that life is delicate (we know it's not), but rather that we have never seen another form of life. That is, every form of life that we've found on Earth can be traced back to a single ancestor. Most of them use DNA/RNA, all use the same left-handed-proteins, etc.

What would really be amazing would be the discovery of a second independent form of life. The spontaneous development of life twice on the same planet would pretty much guarantee that the universe is teeming with it...

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It's much less expensive to look for other trees of life on Earth, but is there any reason why a second one on Earth would be any more likely than a first one on, say, Europa or Titan?

It might be less likely, as we (you, me, and a couple scrillion of our closest relatives) provide robust competition against any other types of life, which may, as you mention, need different chiralities of various molecules, and may have trouble digesting any portion of our biomass.

Well, you have to admit, it's a pretty nice place to live.

I suspect Earth is probably the most amenable place in the solar system for long term life because of a number of features:

* High ambient energy (temperature, non-ionizing radiation)

* Shielded from ionizing radiation

* High atmospheric and oceanic churn

* Stable geology

* Rich dispersion of minerals

Though you are right, the competition on Earth that a second branch of life would face is not insignificant...

Earth is a great place for our type of life to pop up, because out type of life is well adapted to it. Imagine a puddle somehow gaining sentience. It would likely be amazed at how well designed its "world" was: the divet, slow draining and puddle shaped is just right for a puddle like me! The reality is that if we are the only puddle we can imagine, then of course our puddle hole will be the most aminable place in the entire galaxy for puddles.

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