Spike in impacts 3.9 billion years ago may be mathematical mirage, study finds
A barrage of rocks hitting the solar system 3.9 billion years ago could have dramatically reshaped Earth’s geology and atmosphere. But some of the evidence for this proposed bombardment might be shakier than previously believed, new research suggests. Simplifications made when dating moon rocks could make it appear that asteroid and comet impacts spiked around this time even if the collision rate was actually decreasing, scientists report the week of September 12 in the Proceedings of the National Academy of Sciences.
Many scientists think that a period of relative calm after Earth formed 4.6 billion years ago was interrupted by a period called the Late Heavy Bombardment, when rocky debris pummeled Earth and the other planets. The moon’s cratered surface holds the best evidence for this event; scientists have measured radioactive decay of argon gas trapped inside moon rocks to date when