Were a lifeform to develop in methane, or arsenic, or what have you, it would likely bear little or no resemblance to microbes. To assume that it would is to assume that it is DNA based. As a computer programmer, I look at this as a million monkeys at typewriters sort of situation. You can’t assume that self replication can only take one track, that DNA is even required, or that it must be based on hydrogen and oxygen. All you can assume is that it must be capable of self-replication, have an abundant energy source on which to thrive, and an environment that would not be fatal. I don’t think you can assume that life needs a warm creche to develop in before it ventures out to hostile environments. Beyond that it’s random (or directed) events that get you to life.

I find both the ideas – that EBEs must be way ahead of us, or must be way behind us amusing. There’s no reason to assume that we are the measuring standard for the universe. We may be the latest, or the first. There may be nothing but potential out there. Or there may be thriving ecosystems out there that we haven’t discovered. There may be others that we’ve passed over because we didn’t even understand what we were looking at. It’s not like that hasn’t happened before.

Kati: I’m a dreamer, too. Statistically speaking, it’s highly improbable that we’re the only intelligence in the universe. But it’s also probable that if there are intelligent races out there, they’re made of the same stuff as us; analogues of phosphorus and carbon, like arsenic and silicon, simply don’t share the properties that make complex life forms possible. But finding even microbes on another world would be a huge coup for humanity’s understanding of itself and our world.

“What’s much more interesting is that the drama has given us an opportunity to see how a collection of related problems in different areas of science outreach can combine to seriously damage the credibility of a highly-respected scientific institution, and by extension science itself. ”

It’s too bad they jumped the gun, released a possibly false statement about having found something of relevance to extra-terrestrial life (I mean, c’mon, isn’t all life on our planet in that category? If we can evolve, others can evolve.) I agree that the odds are in favor of life coming from an ocean, but there’s too much weirdness out there in the universe to say everything would evolve that way. I just think the odds are highly in favor of it happening that way, but there’s always a miniscule chance that something immensely out of the ordinary could happen. I think of it like the Heart of Gold analogy from Hitchhiker’s Guide to the Galaxy. The odds of finding a sperm whale and bowl of petunias appearing out of nowhere is statistically irrelevant. But who knows? Maybe it’s possible.
The point is it’s not likely, and NASA should really be focusing on the stuff which has a reasonable possibility of happening- or, of being detected, rather than speculating on the possibility of whales appearing in thin air or bowls of petunias. The whole news conference was an intriguing “what if” which was better left to private speculation and further research. This whole thing has marginalized the credibility and importance of NASA still further.

but maybe i’m naive (and not a qualified scientist – although i’ve always considered myself to be a scientist at heart) but it seems sort of limiting and pessimistic to sound so sure of the confines of Life. i think about all the things we know today compared to two hundred years ago. what will we discover in the next two hundred? our planet is proof that Life is determined and scrappy and adaptable and i can only imagine that it is the same way elsewhere. in ways that we can’t even fathom until we find it. i have a hard time saying “our oxygen-rich, watery planet hasn’t fostered the only life out there, just the best” and “If there’s methane-based life on Titan, I doubt it would ever get beyond the microbial stage”. but maybe i’m just a dreamer :)

Although I do sometimes wonder about methane-based life. Many fundamental properties of our cells are made possible by water’s polar, hydrophilic (duh) nature. For instance, membrane lipids agglomerate as they do because they have hydrophobic tails and hydrophilic heads. How would that work with hydrophobic methane as a solvent? Would their membrane lipids (if they have such) simply be turned inside out? If they use DNA, how would handling that differ given that it’s strongly negatively charged? Interesting to ponder.

I get what you’re saying. It makes sense. We on Earth have it easy, and stability is indeed the key to evolution. But do I agree that all life MUST have an ocean nursery in which to begin? No way. I only imagine that our oxygen-rich, watery planet hasn’t fostered the only life out there, just the best. Because we had easy beginnings, life could evolve to its present state where millions of species form an intricate network of ecosystems, and where such beings as dinosaurs, humans, and roasted chickens could evolve. If there’s methane-based life on Titan, I doubt it would ever get beyond the microbial stage. But that certainly doesn’t mean it can’t start.

All that being said, I’ve always loved that Star Trek had the Horta. Boo to the “all-aliens-must-be-carbon-based-hominids” attitude! :-)