The origin of the moon and the single-impact hypothesis I

doi:10.1016/0019-1035(86)90088-6

Icarus

Volume 66, Issue 3, June 1986, Pages 515-535

https://doi.org/10.1016/0019-1035(86)90088-6 Get rights and content

Abstract

Recently the single-impact hypothesis for forming the Moon has gained some favorable attention. We present in this paper a series of three-dimensional numerical simulations of an impact between the protoearth and an object about 0.1 of its mass. For computational convenience both objects were assumed to be composed of granite. We studied the effects on the outcome of the collision of varying the impact parameter, the initial internal energy, and the relative velocity. The results show that if the impact parameter is large enough so that the center of the impactor approximately grazes the limb of the protoearth, the impactor is not completely destroyed; part of it forms a clump in a large elliptical orbit about the Earth. This clump does not collide with the Earth, since the effects, first, of vapor pressure gradients during the impact, and later, of angular momentum transfer due to the rotation of the deformed Earth, have modified the ballistic trajectory. However, since the orbit of the clump comes close to the Earth (within the Roche limit) the clump will be destroyed and spread out to form a disk around the Earth. The amount of angular momentum in the Earth-Moon system thus obtained tends to fall short of the observed amount; this deficiency would be eliminated if the mass of the impactor were somewhat greater than the one assumed here. The scenario for making the Moon from a single-impact event is supported by these simulations.

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The origin of the moon and the single-impact hypothesis I

Abstract

Icarus

Icarus

J. Comput. Phys.

Icarus

J. Comput. Phys.

Shock melting and vaporization of lunar rocks and minerals

The Moon