Home > Astronomy, Earth, Moon, Solar System > New Model Reconciles The Moon’s Earth-Like Composition With The Giant Impact Theory Of Formation

New Model Reconciles The Moon’s Earth-Like Composition With The Giant Impact Theory Of Formation


The giant impact believed to have formed the Earth-Moon system has long been accepted as canon. However, a major challenge to the theory has been that the Earth and Moon have identical oxygen isotope compositions, even though earlier impact models indicated they should differ substantially. In a paper published today in the journal Science online, a new model by Southwest Research Institute (SwRI), motivated by accompanying work by others on the early dynamical history of the Moon, accounts for this similarity in composition while also yielding an appropriate mass for Earth and Moon.

In the giant impact scenario, the Moon forms from debris ejected into an Earth-orbiting disk by the collision of a smaller proto-planet with the early Earth. Earlier models found that most or much of the disk material would have originated from the Mars-sized impacting body, whose composition likely would have differed substantially from that of Earth.

The new models developed by Dr. Robin M. Canup, an associate vice president in the SwRI Space Science and Engineering Division, and funded by the NASA Lunar Science Institute, involve much larger impactors than were previously considered. In the new simulations, both the impactor and the target are of comparable mass, with each containing about 4 to 5 times the mass of Mars. The near symmetry of the collision causes the disk’s composition to be extremely similar to that of the final planet’s mantle over a relatively broad range of impact angles and speeds, consistent with the Earth-Moon compositional similarities.

Full Story: http://www.swri.org/9what/releases/2012/earth-moon-impact.htm
Also: http://www.fas.harvard.edu/~planets/sstewart/Moon.html
Also: https://news.wustl.edu/news/Pages/24148.aspx

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