[Elsie]

Two schools of thought follow: One is that plants DID live before the moon was formed by collision.... The other is that the moon was formed by collision before plants (bateria and the one-celled critters that changed our atmosphere into the clear oxygen/CO2 we have from the murky glop around Venus.)

What we DO know for certain is that in the limited samples of rock that HAVE been returned from the Moon by our astronauts, there has been NO discovery of ANY signs of 'life'.

[Elsie]

Likewise..... where our machines have crawled around on the surface of Mars, NOTHING has been detected by the scientific appratus on board that has shown any 'life' signs.

[Robert A Cook PE]

Well, true, but you wouldn't expect them to be on the mmon either. Regardless of when plants (bacteria) would have started here on earth.

The moon is thought to have been formed bya large galancing collision with an asteroid-sized impact: this melted/blew out 1/6 of the earth back into orbit, where it reconsolidated into a sphere (melting again any fossils that might have been blown out into space....) and then the center core of the moon was re-melted into the seas under future impacts/and that (already thrice melted!) was splashed and shattered again under meteorite impact as the rocks on the moon' surface got hit.

So any early fossils from plants (like the iron deposits in Michigan or the sea-side piles of microbes off Australia) that might have been present simply couldn't survive recognizably as fossils.

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Above all that melting and destruction, we simply have not found any microbe traces as old as the theorectical age of the moon. (Yet, he cautioned!) So, when the moon got blasted out from the earth's crust, there might not have been life created yet here either.