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Moon Formation: Hit-and-run Giant impact scenario

auteur: Ron Miller/Novapix

référence: a-lun99-00026

Image Size 300 DPI: 14 * 71 cm

The giant-impact hypothesis, sometimes called the Big Splash, or the Theia Impact suggests that the Moon formed out of the debris left over from a collision between Earth and a body of the size of Mars, approximately 4.5 billion years ago. Unfortunately, samples taken from the Earth and from the Moon show that the ratio of the Earth's and the Moon's oxygen isotopes is nearly identical. And a fresh analysis of lunar samples taken by the Apollo missions show that the Moon and the Earth share a very similar isotope ratio of the metal titanium... All which should not be the case, if the Big Splat theory is correct. Researchers (A.Reufer et al.) have proposed a variation on the Big Splat. They have suggested that instead of a collision with a slow-moving body like Theia, a much larger and faster-moving body hit the earth a glancing blow. Unlike Theia — which would have been largely sacrificed in the creation of our Moon — this new body would have lost only a small amount of material in the collision. After smacking the Earth, the planet would have continued on its way The result of this glancing blow would have been a much hotter disc of debris circling the Earth, but with still enough material to have coalesced into a body the size of the Moon. Since most of this material would have originated from the Earth, this would neatly explain the similarities between the isotope fractions.

Keywords for this photo:

ASTRONOMY - COLLISION - EARTH - EARTH FROM SPACE - FORMATION - ILLUSTRATION - IMPACT - MOON - PLANET - PRECAMBRIAN - PRIMITIVE EARTH - RING - SATELLITE - THEIA -