It seems this particular debate goes round and round in circles for ever.

Surely the whole point about life and I mean LIFE and not precursor organic chemicals is that there needs to be a certain range of conditions in existence in a particular place or places for certain minimum period of time for the Chemistry to work in order for life to develop. Now of course it is possible that given the size of the universe that this process may well have happened in more than one place at several different times. It is possible that there it may have happened in more than one place within our own Galaxy.

The point is until we can lay down a series of specifications that can determine what sort of place, with which sort of conditions, needs to exist for how long for living cells to emerge then we cannot say whether one place or another was a viable cradle for life. It therefore follows we cannot on the one hand suggest other places in space ARE SUITABLE birth places for life, whilst on other hand we CANNOT for the same reason say the early Earth was UNSUITABLE as a birth place for life.

However it is not enough to vaguely suggest against some imprecise criteria that the early Earth WAS NOT an adequate place for life to emerge unless you can also propose in your argument the sort of place which would have been necessary to produce life on its own. Simply saying that this or that astronomical body contains a few useful organic chemicals PROVES NOTHING. For the simple reason, it may be easy for those precursor chemicals to form in all sorts of places but the step to living cells is a very different matter. A comet containing formaldehyde might orbit a star for billions of years but never produce a single bacterium by itself.

Only once you have a viable alternate location or set of locations outside of earth, each of which can be demonstrated as being a better place for life to have originated than here, can you then move on to the next phase of the argument. Which of course is the probability of seeding. In other words, could life which formed somewhere else have been transported here before life here got going on its own accord? Remember we are talking LIFE here, that is cells or spores being transported across interstellar distances (not precursor chemicals). This means you have to go back to your first argument to determine how many places are likely to have originated life based on the required criteria.

Now you run into a trap. If you lower the bar to increase the number of places where life can emerge then it is likely you will bring the early Earth within those boundaries, thus making abiogenesis more reasonable. If however you raise the bar to exclude the early earth then you reduce the number of locations where life can emerge. The consequence of that is a less dense distribution of seeding sources, consequently fewer seeding packages being ejected into interstellar space and a reduced probability of one of those packages actually hitting this planet. Not only that but this reduced population of source locations will increase the mean interstellar distance those packages of life will have had to travel, which in turn increases the probable transit time, thus giving this planet more time to evolve life all on its own. So once again abiogenesis comes back into the frame

Only after you have got good numbers for all of this, can you start discussing if this or that transport mechanism might work and whether the spores could survive an interstellar transit lasting maybe 100K to 1M years.

The trouble is when you go back to basics - how do you prove that some other place was better for life to emerge than here? When we have not yet discovered any such place. Life is here, we know that. There is no reason to suppose that all the basic chemicals were not already around in the solar system even if this planet may have collected them at different stages during its early formation. Then that would still be classed as abiogenesis and not Panspermia. So far we have not found another place that is demonstrably a better place to be the cradle of life, which means that at the moment the Rare Earth hypothesis is just as valid (perhaps more so) than your Universe Teeming with Life.

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Note 1. All requests for planetary demolition must now be submitted in quadruplicate on form UX-565/B4 and be counter-signed by the assistant administrative officer for interstellar traffic calming - department QG-7. Subject to approval by the chief planning officer and the infrastructure development coordination sub-committee.