(May 22, 2017 at 1:24 pm)Whateverist Wrote: But that only supports the notion that life arising on other planets may wind up on planets where life has already arisen.  If the conditions are right to support the alien forms, it would probably also initiate abiogenesis here.

Not necessarily. We don't know on average how long it takes for abiogenesis to occur in environments that otherwise could have sustained life that has already arisen. It could be hundreds of millions of years. The earliest evidence of life on earth seem to postdate the earliest evidence of relatively mild conditions on earth by 300-500 million years. That's a period of time roughly equal in length to that between Cambrian explosion and now. So if abiogenesis were to be allowed to occur on all bodies in the solar system where they can occur, their timing may still differ by hundreds of billions of years or even billions of years.

I have seen estimates that says ejecta from major meteoritic impact on a large rocky body in the solar system will typically take 30 million years before accreting onto another major body. Another study say that during the 100-200 million years before first evidence of life on earth, inner solar system experienced a particularly severe period of meteror bombardment during which major impacts capable of ejecting debris at escape velocities of rocky planets and moons occur on average once every 100 years on each major inner solar system bodies.

So the upshot seems to be there is plenty of time and opportunity for the products of earlier abiogenesis in the solar system to get blasted from the body of their origin, travel through solar system, and land on another body long before native abiogenesis has occurred on the other body.

We don't know how long it takes for new life introduced to a hospitable environment to propagate through all the available niches at the destination planet and potentially forestall or severely constrain an successful independent abiogenesis event on the destination planet. But even if that takes many hundreds of millions of years, it still does not seem statistically prohibitive for such panspermia to have snuffed out many potential abiogenesis evens in our solar system.

When I first heard the term imagine my disappointment when I found out what it actually meant . . .

(May 22, 2017 at 3:50 pm)vorlon13 Wrote: When I first heard the term imagine my disappointment when I found out what it actually meant . . .

Panspermia never meant jerking off on every asteroid or moon, Vor.

Does anyone indicate what is supposed to have been spermed to earth?

(May 22, 2017 at 5:41 pm)mh.brewer Wrote: Does anyone indicate what is supposed to have been spermed to earth?

From a Peter Pan, apparently.

I'm still fascinated by the notion that life can only evolve by only one possible genetic framework.
IE, do you guys believe that other life on other planets could have a completely incompatible tree of life to ours?
If so, if panspermia happened concurrently with our own independent evolution, why then, is there only one tree of life?

Did our conditions favour only one? Shouldn't it be the home grown advantage, logically speaking?

(May 22, 2017 at 12:48 pm)Neo-Scholastic Wrote: My initial thoughts on it is that it sounds plausible until we consider the vast distances and likely velocity of a complex molecule. Basically, not only must it evolve somewhere stable, some catastrophic event must accelerate it to near light speed without damaging it, and is has to be close enough not to be dispersed into insignificance and/or be precisely aimed in our direction at just the right time in our planet's development. The odds are staggering that a sufficiently complex molecule could be so lucky to beat a homegrown solution.

Hmm.... this from the guy who thinks god played in the dirt.

Min, God took a dump and we are his cheeky little shits! Hehehe

(May 22, 2017 at 10:11 pm)ignoramus Wrote: I'm still fascinated by the notion that life can only evolve by only one possible genetic framework.
IE, do you guys believe that other life on other planets could have a completely incompatible tree of life to ours?
If so, if panspermia happened concurrently with our own independent evolution, why then, is there only one tree of life?

Did our conditions favour only one? Shouldn't it be the home grown advantage, logically speaking?

I guess I'm not sure what is meant by 'incompatible'.

It turns out, for instance, silicon based life is vastly less probable than carbon based.  The chemistry of the element silicon just isn't complex enough.

I'm not sure that anyone has definitively worked out that a double helix of DNA is favored over some other geometry, btw.  I recall 'Moties' (fictional) were noted to have genetic information conveyed via an arrangement of disks and rods.  Obviously, life forms with a totally different 'geometry' of their heritable elements will be certainly incompatible with our double helix arrangement, even if some of the chemicals were the same.

Why hasn't life evolved more than one genetic geometries?
Earth has had billions of years of trial and error. Why only one prospered?
It's like the rest cannot kick off into the replication stage?

Since the elements are universal, I'm going to extrapolate and say that all life must use our tree of life geometry.
By that I mean, it isn't ours, but the only one that can work. Anywhere.