Sent in by Robert – go to https://www.nature.com/articles/d41586-018-01074-6 … which questions the idea of the Late Heavy Bombardment, a theory which has had a somewhat extended life. The bombardment is thought to have occurred half a billion years after our planet was formed. In the process all hell was let loose as a barrage of asteroids remodeled the surface of the Earth. Only after this stream of space debris had quietened down was Life able to evolve. However, it seems mounting evidence has caused a body of researchers to question the hypothesis. They think it was all over a few hundred million years after the formation of the Earth and the Moon. In other words, the idea is kept intact but its duration is reduced. It is altogether a rather strange theory in any case as the common ploy of its adherents is that all evidence of it has been erased by Plate Tectonics. Another problem has been the conflicting dates produced by different dating methodology. Instead ot question the dating techniques themselves, which might throw up a few rabbits that would be unwanted, they have produced a sort of watered down version of the hypothesis. Its as if they can't come out straight and say its all moonshine. Robert's second link is not so squeamish – go to https://crev.info/2018/01/late-heavy-bombardment-myth-dying/ … and Robert comments – what if they were electric? How would that affect the dating. Depends on how much evidence there is of cratering I suppose – which would be minimal if Plate Tectonics was a reality.