The Late Heavy Bombardment (LHB) was a period approximately 3.8 to 4 billion years ago during which the Moon, Earth, Mercury, Venus, and Mars were subjected to many impacts from space. The evidence for this and the dating comes mainly from analysis of the craters of the Moon and Moon rocks. It formed some craters the size of continents. This bombardment came after a relatively calm period of several hundred million years. It is not yet clear exactly what brought about the renewed bombardment. One possibility is that Jupiter's orbit shrank, causing it to clean out the outer edges of the asteroid belt, a portion of which would have been sent careening into the inner solar system. Or somewhere in the Solar System a big collision created a lot of flying fragments which became new asteroids. Recent computer models also suggest that resonances and perturbations caused by the four large outer planets settling into their current orbital configurations could have displaced large volumes of material into the inner solar system. Bulk silicate composition (estimated wt%) SiO2 44. ... Earth (IPA: , often referred to as the Earth, Terra, the World or Planet Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth largest. ... Note: This article contains special characters. ... (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... Image of the main asteroid belt between the orbits of Mars and Jupiter. ... Major features of the Solar System (not to scale): The Sun, the eight planets, the asteroid belt containing the dwarf planet Ceres, outermost there is the dwarf planet Pluto (the dwarf planet Eris not shown), and a comet. ...

On Earth, the Late Heavy Bombardment would have produced:-

22,000 or more impact craters with diameters > 20 km

about 40 impact basins with diameters about 1000 km

Several impact basins with diameter about 5,000 km

with a serious environmental damage event about every 100 years. Tycho crater on Earths moon. ... This article is about impact craters. ...

On the Moon, the Late Heavy Bombardment is associated foremost to the Nectarian and Lower Imbrian lunar geologic epochs. The Nectarian Period of the lunar geologic timescale runs from 3920 million years ago to 3850 million years ago. ... In the Lunar geologic timescale, the Lower Imbrian epoch occurred between 3850 million years ago to about 3800 million years ago. ... The lunar geologic timescale (or perhaps more properly the selenologic timescale) divides the history of Earths Moon into six generally recognized geologic periods: Copernician Period : 1100 MY to present Eratosthenian Period : 3200 MY to 1100 MY Upper Imbrian Epoch : 3800 MY to 3200 MY Lower Imbrian Epoch : 3850 MY...

External links

• G. Jeffrey Taylor (August 24, 2006). Wandering Gas Giants and Lunar Bombardment.
• Barbara Cohen (January 24, 2001). Lunar Meteorites and the Lunar Cataclysm.
• New Insight into Earth’s Early Bombardment - Space.com, 17 April 2006.
• Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets, Gomes, Levison, Tsiganis, Morbidelli - Nature 26, May 2005.
• Late Heavy Bombardment was asteroidal, not cometary, The Geological Society, March 4, 2002.
• Britt, Robert Roy, "Evidence for Ancient Bombardment of Earth," 24 July 2002.

Bulk silicate composition (estimated wt%) SiO2 44. ...