Late Heavy Bombardment - 'The Late Heavy Bombardment (commonly referred to as the lunar cataclysm, or LHB) is a hypothetical event around 4.1 to 3.8 billion years ago. During this event an extraordinary number of the impact craters on the Moon would have formed, and by inference an extraordinary large number of impacts on Earth... Extrapolating lunar cratering rates to Earth: 22,000 craters with diameters >20 km, about 40 > 1,000 km, several > 5,000 km'
The Hadean, being an informal not stratigraphically defined eon, is here defined as the period from the Tellus (proto-Earth)-Theia impact (circa 4520 mya) to the end of the LHB (Late Heavy Bombardment) period,about 3800 bya. Recently, Goldblatt et al. 2010 have proposed an even earlier eon, the Chaotian,for events pertaining to the formation of the Solar System
The Late Heavy Bombardment (abbreviated LHB and also known as the lunar cataclysm) is a hypothetical event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, corresponding to the Neohadean and Eoarchean eras on Earth. During this interval, a disproportionately large number of asteroids apparently collided with the early terrestrial planets in the inner Solar System, including Mercury, Venus, Earth, and Mars.