Late Heavy Bombardment

The Late Heavy Bombardment (LHB) or lunar cataclysm happened about 4.1 to 3.8 billion years ago. During this time, a large number of impact craters formed on the Moon. By inference, the same thing happened on Earth, Mercury, Venus, and Mars as well.Fazekas, Andrew (March 24, 2015). Observe: Jupiter, Wrecking Ball of Early Solar System. National Geographic. Archived from the original on March 14, 2017.

The evidence for this event comes from the dating of lunar samples. This shows that most impact melt rocks formed at that time. Many hypotheses have been suggested to explain how asteroidal or cometary material got into the inner solar system, but no consensus yet exists.Simpson J.A.; Weiner E.S.C. 1989. Jupiter. Oxford English Dictionary. Vol. 8 (2nd ed), Clarendon Press. ISBN 978-0-19-861220-9 

One popular theory is that the gas giant planets (or at least Jupiter) migrated in orbit at this time: see Grand tack hypothesis. This caused objects in the asteroid belt and/or Kuiper belt to be forced into orbits which reached the terrestrial planets. 

Some think that the apparent clustering of impact melt ages near this time is an artifact of sampling.Taylor G. Jeffrey 2006. Wandering gas giants and lunar bombardment

This topic is part of the formation and evolution of the Solar System.

 Related pages 
 Life timeline
 Nature timeline

 References 

Category:Moon
Category:Earth

Category:Impact craters
Category:Hadean
Category:Impact events