PROBLEMS OF CO-ACCRETION MULTIPLE-IMPACT HYPOTHESIS OF MOON FORMATION

Abstract

The hypothesis that the Moon formed from a near-Earth swarm, formed by the gravitational capture of bodies from the planet’s feeding zone during planetary accumulation period and replenished with material ejected by the impacts of large bodies, was proposed long ago. However, the substantiation of this hypothesis is far from complete, although it is highly relevant given the lack of a comprehensive theory of the Moon’s origin. In this work, a numerical simulation of the impacts of large bodies on the Earth at different velocities was carried out and the masses and velocities of material ejected into ballistic and
heliocentric orbits, as well as the concentration of iron in these ejections, were determined. The total mass of ejecta during the growth of Earth, starting from the moment when it accumulated half of its present mass, is more than ten lunar masses at impact velocities slightly exceeding escape velocity, and increases with increasing impact velocity. The probabilities of multiple passes of fragments ejected into heliocentric orbits through the Hill sphere, the complexities of the co-accretion multiple-impact model and the prospects for its development are considered.