The origin of the Moon: a gravitational instability? Conference Paper uri icon


  • The origin of the Moon has long been of interest and although the Giant Impact theory is currently the preferred explanation unequivocal supporting evidence has been lacking The megaimpact model is based on the concept of a collision with the Earth of a body whose mass exceeded one to two Martian masses Such an idea was suggested by Cameron and coauthors and then developed mainly numerically in a number of papers In our opinion however the megaimpact hypothesis belongs to a rare class of catastrophic hypotheses that are based on low-probability random events Here we consider an opposite model a regular evolution process The formation of the Earth--Moon system is re-examined by considering the stability of the common preplanetary disk of gas and dust with a mass of about 100M oplus and a radius of about 100R oplus In the framework of this model the preplanetary disk forms self-gravitating massive sim 10-30 M oplus gaseous proto-Earth and proto-Moon through a gravitational instability of the gas accompanied by settling and coagulation of dust grains to form solid cores The larger part of the initial mass of the Earth--Moon system as well as the initial mass of protoplanets of the Earth s group were probably blown away due to intensive thermal emission of the early Sun It is shown that a collective process forming the basis of the gravitational instability hypothesis solves with surprising simplicity the two main problems of the dynamical characteristics of the Moon which are associated with its significant mass and large orbital

publication date

  • January 1, 2006