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'
Late Heavy Bombardment: construction in the destruction? Comet and asteroid barrage may have given Martian life a leg-up Where Earth nurtured life, Mars (as far as we know) has not. But a seemingly destructive event some four billion years ago may have given Martian life the boost it needed.