Presentation on theme: "Late Heavy Bombardment Or, Kablooie!. The main piece of evidence for a lunar cataclysm comes from the radiometric ages of impact melt rocks that were."— Presentation transcript:
Late Heavy Bombardment Or, Kablooie!
The main piece of evidence for a lunar cataclysm comes from the radiometric ages of impact melt rocks that were collected during the Apollo missions. The majority of these impact melts are believed to have formed during the collision of asteroids or comets tens of kilometers across, forming impact craters hundreds of kilometers in diameter. The Apollo 15, 16, and 17 landing sites were chosen as a result of their proximity to the Imbrium, Nectaris, and Serenitatis basins.radiometric agesApollo Imbrium NectarisSerenitatis
Mercury & The Moon Studies of the highland crater size distributions suggest that the same family of projectiles struck Mercury and the Moon during late heavy bombardment.  If the history of decay of late heavy bombardment on Mercury also followed the history of late heavy bombardment on the Moon, the youngest large basin discovered, Caloris, is comparable in age to the youngest large lunar basins, Orientale and Imbrium, and all of the plains units are older than 3 billion years.   Caloris 
Mercury -> <- Moon
A series of simulations by Gomes et al. start with a Solar System where the gas giant planets are in a tight orbital configuration.  This configuration is in itself stable, but assuming a rich trans-Neptunian belt, stray transneptunians interacted with these planets, causing them to migrate slowly during a time of several hundred million years. Jupiter is predicted to migrate inward, whereas the other planets go outwards. By this migration, the Solar System became catastrophically unstable when Jupiter and Saturn reached a 2:1 orbital resonance, causing the outer Solar System to reconfigure rapidly to a wide jovian system. As these planets migrated, resonances would be "swept" through the asteroid belt and Kuiper belt. These resonances would increase the orbital eccentricity of the objects, allowing them to enter the inner Solar System and impact with the terrestrial planets.  Recent work suggests that the impactors which caused the LHB were sourced from a now almost entirely depleted inner band of the asteroid belt, close to MarsSolar System trans-Neptunian beltorbital resonanceorbital eccentricity asteroid beltMars
Planet V hypothesis Planet V simulations posit the former existence of a fifth planet, smaller than Mars, in the inner Solar System, outside the orbit of Mars but inside the asteroid belt. The orbit of this planet was theorized to be nearly circular but meta-stable, and was disrupted at the time of LHB, becoming eccentric, starting to sling asteroids about to collide with the inner planets before ultimately plunging into the Sun.asteroid belt
Fifth gas giant hypothesis Another hypothesis has posited an additional fifth gas giant in a trans-Saturnian orbit between Saturn and Uranus. The ice giant is theorised to have been flung out of the Solar System after a close encounter with Jupiter, which lost angular momentum as a result and receded further away from the Sun, preserving the relative orbital stability of the inner Solar Systemangular momentum
Life on Earth ???? If a lunar cataclysmic cratering event were truly to have occurred on the Moon, the Earth would have been affected as well. Extrapolating lunar cratering rates  to Earth at this time suggest that the following number of craters would have formed:    22,000 or more impact craters with diameters >20 km (12 mi),impact craters about 40 impact basins with diameters about 1,000 km (620 mi),impact basins several impact basins with diameter about 5,000 km (3,100 mi), Serious environmental damage would occur about every 100 years, although life is not known to have existed on Earth at this time.
Eta Corvi The IRAS satellite detected an excess of infrared radiation from this star, beyond what would normally be expected for a stellar object of this class.  Observations in the submillimetre band confirmed the presence of excess dust in orbit around the star having about 60% of the mass of the Moon and a temperature of 80 K. The data indicated a debris disk with an estimated maximum radius of 180 A.U. from the star, or 180 times the separation of the Earth and the SunIRASexcess of infrared radiation submillimetre bandMoondebris diskA.U.