Spread out the napkin on the table... who's got a pen...?<quoted text>
....and since the planet earth has been continuously bombarded by intersteller debris in the form of asteroids, comets, etc since being formed, those compounds have 'hitched a ride' here as well.
OK, so it looks like life developed on the earth about a billion years or so after the earth was formed. Moreover, it looks like life developed on the earth within a few hundred million years after life could have possibly survived. Maybe a lot less. Now the fastest intersellar meteroids seems to travel at about 50 miles per second, and light travels at about 200,000 miles a second, so in 200 million years that meteroid could possibly have travelled about 25,000 light years, which is only about 1/5th of the diameter of our galaxy.
Well, that is a lot of room in human terms, but those projectiles would have to have been very numerous, and of amazing aim to hit the moving target of the earth, and have enough pieces left, not incinerated to plant it's germ seed here. So I'd say that while panspermia is possible, it might not even be statistically as likely, as life just having come out of abiogenesie right here in River City, folks.
If the numbers were a bit different, and life had taken billions of years to show up after the earth was ready, then panspermia would be more plausible. Anyway, play with those numbers. Maybe I made a mistake in my head. In any case it certainly looks like life would have had to exploded out along with the big bang itself, if panspermia has any chance of explaining it, otherwise the origin of life would have had to be very much more local. Don't forget, those other stars were spreading out and getting further and further away all the time.