E-belt asteroids

The E-belt asteroids were the population of a hypothetical extension of the primordial asteroid belt proposed as the source of most of the basin-forming lunar impacts during the Late Heavy Bombardment.

The E-belt model was developed by William F. Bottke, David Vokrouhlicky, David Minton, David Nesvorný, Alessandro Morbidelli, Ramon Brasser, Bruce Simonson and Harold Levison. It describes the dynamics of an inner band of the early asteroid belt within the framework of the Nice model.

The extended-belt asteroids were located between the current inner boundary of the asteroid belt and the orbit of Mars with semi-major axis ranging from 1.7 to 2.1 astronomical units (AU). In the current Solar System most orbits in this region are unstable due to the presence of the ν6 secular resonance. However, prior to the giant planet migration described in the Nice model the outer planets would have been in a more compact configuration with nearly circular orbits. With the planets in this configuration the ν6 secular resonance would be located outside the asteroid belt. Stable orbits would have existed inside 2.1 AU and the inner edge of the primordial asteroid belt would have been defined by Mars crossing orbits.

During the migration of the giant planets the ν6 secular resonance would have moved inward as Saturn moved outward. Upon reaching its current location near 2.1 AU the ν6 secular resonance and other related resonances would destabilize the orbits of the E-belt asteroids. Most would be driven onto planet-crossing orbits as their eccentricities and inclinations increased. Over a period of 400 million years impacts of the E-belt asteroids yield an estimated 9-10 of the 12 basin-forming lunar impacts attributed to the Late Heavy Bombardment.

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