[X] My Assistant

[jaredGalen]

Thought this article title was a little over the top, the kind of one you would
expect to see followed by lots of exclamation marks.

Interesting article though.

"IF LIFE exists on Titan, Saturn's biggest moon, we could soon know about it - as long as it's the methane-spewing variety. The chemical signature of microbial life could be hidden in readings taken by the European Space Agency's Huygens probe when it landed on Titan in January."

http://www.newscientistspace.com/article.ns?id=dn7716

[dvandorn]

Personally, I think that we will find biogenesis processes on a variety of worlds and in a variety of non-planetary environments. But we will find that most of them have progressed only so far before they have run across some limiting factor that has arrested the process (or slowed it into virtual arrest) at very primitive levels.

For example, we can speculate all we want on the early biogenetic processes on Earth, but we *know* that Earth is a somewhat freakish exception in its overall climatic uniformity. The only reason the Earth does not have cyclic extremes of climate (as Mars does) is because our Moon keeps our rotational precessions from wandering all over the place -- our axial tilt is maintained by the Moon's gravitational influence. An Earthlike planet in another star system might develop exactly the way Earth did, with exactly the same range of elements and minerals and water and temperatures -- but without a large moon, its axial tilt would wander around and subject its surface to cyclic periods when one whole hemisphere never sees sunlight for thousands of years at a time.

That kind of thing might not stop biogenesis cold, but I bet it slows it down a lot. And that "progress" towards multi-cellular organisms might be wiped out every few hundreds of thousands of years when the climate changes and favors only the continued development of extremophiles that are so constrained by their adaptations to extreme environments that they are "blind alley" developments as far as complex life forms are concerned.

Frankly, I think the only Earthlike bodies we're going to find out there that have stable long-term climates will be moons of gas giants that have been dragged into their stars' habitable zones as their primaries migrate in toward their stars. And if it really *does* require a few billion years of "simmering" before multi-cellular organisms can arise from a soup of primitive single-cell organisms, then the limiting factor of climate stability might be the major constraint on "M"...

-the other Doug