Moon origin: the impact-trigger hypothesis.
Abstract
The impact-trigger hypothesis proposes that an unusually large planetesimal impact on the early Earth initiated lunar formation. Lunar properties favoring this hypothesis are listed. A common objection, that the impact is ad hoc, is refuted. The intense early bombardment averaged during Earth's formation was several 109times the present meteoritic mass flux, consistent with a giant impact. Three different physical effects possibly involved in lofting debris into a circumterrestrial cloud are discussed. These effects create different impact-trigger submodels. An impactor mass of a few MMoon to ≡MMars is estimated from three independent lines of evidence. Numerical models of ejecta velocity distributions indicate that a few lunar masses of debris could have been ejected at speeds between circular and escape velocities; second burn gas expansion effects may increase this value and help the material achieve orbit.
- Publication:
-
Origin of the Moon
- Pub Date:
- 1986
- Bibcode:
- 1986ormo.conf..579H
- Keywords:
-
- Earth-Moon System;
- Impact;
- Lunar Evolution;
- Meteoroids;
- Astronomical Models;
- Constraints;
- Ejecta;
- Iron;
- Stochastic Processes;
- Lunar and Planetary Exploration;
- Moon:Origin