[ExI] Life must be everywhere!

[BillK]

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

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.
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BillK