Portal de Periódicos da CAPES

Forming a Moon with an Earth-like Composition via a Giant Impact

2012; American Association for the Advancement of Science; Volume: 338; Issue: 6110 Linguagem: Inglês

10.1126/science.1226073

1095-9203

R. M. Canup,

Astrophysics and Star Formation Studies

Forming the Moon from Earth It is thought that the Moon formed after a Mars-sized planet hit Earth about 4.5 billion years ago. Computer simulations of this event predict that the Moon was produced primarily from material from the impacting planet. However, the Moon has a similar composition to that of Earth, and the impacting planet would likely have had a different composition. Prior models assumed that the impact left the Earth-Moon system with the same angular momentum as it has today (see the Perspective by Halliday ). Ćuk and Stewart (p. 1047 , published online 17 October; see the cover) show that the angular momentum of the Earth-Moon system could have decreased by half after the Moon-forming impact, opening the door to new impact models. For example, simulations suggest that high-velocity impacts onto a fast-spinning early Earth can lead to a Moon formed primarily from Earth's mantle. Canup (p. 1052 , published online 17 October) considered instead lower-velocity impacts by planets comparable in mass to the proto-Earth, which could generate a Moon and an Earth with similar compositions.