[ExI] Panbiogenesis

[Eugen Leitl]

On Fri, Jan 27, 2012 at 10:02:38AM +0000, Anders Sandberg wrote:

> Consider a biosphere lasting 5 billion years, that manages to seed just  
> one other planet out of (say) 10 billion available in the galaxy.  That  
> means a probability of 1 in 50 billion billion per year. A slightly  
> higher probability in this model, and more planets will be seeded and  
> the galaxy will "quickly" be colonized.

There's no known mechanism for interstellar transfer of
impact ejecta though. In case Oort cloud is life-bearing
this might be different, as there could be interactions
with other star's extended icy body clouds which pass
through vicinity.

Are you aware of any panspermia papers which deal with
interstellar Oort-Oort transfers? 

> One can try to bound probabilities in various ways, but things are very  
> uncertain. However, it is not too hard to build a joint model of  
> spontaneous biogenesis and panspermia, and then plug in our sole data  
> point of when life appeared on Earth. That produces a fairly thin  
> maximum likeliehood ridge in parameter space, showing a relationship  
> between the panspermia and biogensis probabilities.