[ExI] Life must be everywhere!

Kelly Anderson kellycoinguy at gmail.com
Fri Apr 13 01:41:50 UTC 2012


On Thu, Apr 12, 2012 at 12:07 PM, BillK <pharos at gmail.com> wrote:
> 2012/4/12 Alfio Puglisi wrote:
>> The last sentence doesn't really follow from the rest.  Whatever the number
>> of rocks which have visited us from other planets, one has first to suppose
>> that those planets were filled with microorganisms to begin with.
>
> Yes, you have to assume that life appearing is not a one-off
> occurrence on Earth alone.

And we just don't know... It will take us a long time to get farther
out than the 65,000,000 year old rocks... and who is to say that such
events didn't happen 3.8 or 2.5 billion years ago as well, they
probably did. So we've basically got to outrace all rocks hurtling
away from our solar system for 4.0 billion years worth before we'll
have a solid clue as to whether earth was the main source of life.

The really bad news here is that this makes alien microbes potentially
far more dangerous than if they were a completely separately evolved
phenomena, as they will have just enough in common with us to be
potentially hazardous.

> But even then, earth life will almost certainly have dispersed to
> other star systems.

This seems highly likely, and more so with each new study along these lines.

> The authors say in the abstract:
> We also estimate the transfer velocity of the micro-organisms in the
> interstellar space. In some assumptions, it could be estimated that,
> if life has originated $10^{10}$\ years ago anywhere in our Galaxy as
> theorized by Joseph and Schild (2010a, b), it will have since
> propagated throughout our Galaxy and could have arrived on Earth by
> 4.6 billion years ago. Organisms disperse.

One interesting side effect of this kind of information is that even
if some kind of molecular replicator evolved on earth independently,
it seems likely that any life form that could survive the trip from
another planet would likely be made of stronger stuff than the locally
evolved life. This would tend to indicate that even if non-DNA life
forms evolved in places that would be friendly to DNA based life, that
DNA based life landing there would likely out compete the local
alternative. (This assumes that DNA is the biggest bad ass out
there...)

Likewise, should we develop silicon based artificial life capable of
the same sort of trip, it might wipe out DNA based life throughout the
galaxy wherever it landed. Artificial life seems likely to be more
durable and bad ass than DNA. So, should artificial life be generated
on earth or anywhere else, it seems like the long term outlook for all
organic life is dim.

I think that is is likely that DNA based life originated on earth. I
also find it plausible that whatever arose here on its own got killed
or assimilated by alien invaders. So maybe Hollywood got it right
after all, scary.

>From the article a few weeks ago, it seems like prokaryotic life is
far more likely to survive outer space than eukaryotic life... so it
could be that eukaryotic life is rather rarer out there (even if
seeded by us).

It's all fascinating stuff. The big unanswered question is whether
life originates spontaneously anywhere that the conditions are
favorable... This is a question that might remain unanswered for a
very long time. I think we'll have to explore quite a bit of the
galaxy before we can really answer the question.

For me, the best evidence for galactic seeding of the early earth is
how very quickly life evolved after the earth cooled to the point that
it could sustain life at all. The best estimates are 100,000,000 years
or so... and if you look at entropic curves throughout history, this
is kind of the great outlying piece of data. The development of
prokaryotic life so suddenly just doesn't seem like it belongs on the
same Law of Accelerating returns curve as everything else that's
happened before and since, that we know about. So if, like me, you
really think Kurzweil and company are really onto something that is
basic physics, you are somewhat forced to take intergalactic
panspermia with a little more seriousness than just laughing it off as
pure nonsense.

I know I have argued against it before here... and those were
relatively good arguments too... but this new data I think bolsters
the panspermia argument.

-Kelly




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