Illustration of the very early Earth (and the Moon off to the left) during the period known as the Late Heavy Bombardment (4.0 - 3.8 billion years ago). In geological terms it coincides with the Archaean era, which followed the earlier Hadean era. Water is known to have existed even at this early stage. The Late Heavy Bombardment was characterised by more than 200 million years of heightened asteroidal and cometary impacts on the innermost planets.