I would think there are lots of micron-sized particles leaving our solar system now. A gray goo capable of passive or even active solar sailing or of other, active means of panspermia would obviously seem to have lots of evolutionary advantages. Due to co-evolutionary pressure you can obviously get arbitrarily complex autoreplicators, up to the level of sentience. (As autoreplicators can't emerge spontaneously, they will obviously have potential for advanced infoprocessing capabilities right from the start. Since brittle autoreplicators are containable, the emerged autoreplicators will be nonbrittle in respects to evolutionary optimization).
P.S. You non-believers in the gray goo being dangerous are really scary. Arriving at rash conclusions, often riddled with obvious logical flaws and basing further course of action upon these is imo dangerously unresponsible behaviour. We need nano-CERT, and quick.
Spike Jones writes:
> of course, interstellar space is about 5 orders of magintude larger than
> interplanetary space. i need to do the calcs, but intuition tells me
> a meteor could not punch material out of the sun's gravity well, and even
> if so, the simple relicator would not survive the jillions of years of
> wandering thru i.s. space. guess that would explain why we have
> never had one fall on this planet.
> a grey-gooed double star might be able to goo its neighbor perhaps. spike