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Scientists at PMO Unveil Evidence of the Lunar Giant Impact

Study of lunar meteorites lead by a team of Chinese scientistsprovides compelling evidence for the Lunar GiantImpacthypothesis, which suggests that the Moon formed out of the debris left over from a collision between Earth and an astronomical body the size of Mars, approximately 4.5 billion years ago.

Scientists at the Purple Mountain Observatory of CAS performed in situ isotopic analysis on three lunar meteorites loaned from NASA and discoveredan extremely high degree ofchlorine isotopic fractionation, which is a strong indication of ultra-high-temperature and ultra-high-energy conditionsprevailing during a giant collision between astronomical bodies.

Wang Ying from the research team said chlorine isotopic fractionation is a process in which chlorine-35, the lighter isotope of chlorine, relativelyevaporates more than the heavier isotope chlorine-37 at high temperatures.

The high degree of chlorine isotopic fractionation in lunar meteorites further confirmed that the moon originated from a giant impact, Wang said.

"The giant-impact hypothesis offers rational interpretationsto many observations, such as the moon's rotation speed and the relatively large size of the moon compared with the Earth," said Hsu Weibiao, another scientist from the observatory.

In addition, lunar rocks returned by Apollo Astronauts contain the same oxygen isotope composition as the Earth. In other words, the two bodies share the same set of ‘DNA’",Hsu said.

The research project started in 2011 and the result was recently published on Scientific Reports in early April.

 

 

Fig.1 Petrographic and mineralogic characterization of the apatite grain in the feldspathic breccia Dhofar458. (a) Back-scattered electron (BSE) image of the apatite grain, showing that it was subhedral and partially corroded by recrystallized anorthite-augite intergrowths. The rectangular pits are from NanoSIMS analyses. The spot numbers are labelled beside the pits. (b) Raman spectra of the apatite grain, exhibiting characteristic bands of F,Cl-apatite at 963, 429, 580, 591, and 1050 cm 1. Abbreviations: Ap, apatite; An, anorthite; Aug, augite; Ol,olivine. (Image By HSU Weibiao)