Editing Giant-impact hypothesis (section)

=== Composition ===
A number of compositional inconsistencies need to be addressed.

* The ratios of the Moon's volatile elements are not explained by the giant-impact hypothesis. If the giant-impact hypothesis is correct, these ratios must be due to some other cause.<ref name="4045.pdf"/>
* The presence of volatiles such as water trapped in lunar [[basalt]]s and carbon emissions from the lunar surface is more difficult to explain if the Moon was caused by a high-temperature impact.<ref name=nature454/><ref>{{cite journal | title = KAGUYA observation of global emissions of indigenous carbon ions from the Moon | journal = Science Advances | date =  6 May 2020 | first = Shoichiro | last = Yokota |author2=Kentaro Terada |author3=Yoshifumi Saito |author4=Daiba Kato |author5=Kazushi Asamura|author6=Masaki N. Nishino |author7=Hisayoshi Shimizu|author8=Futoshi Takahashi|author9=Hidetoshi Shibuya|author10=Masaki Matsushima|author11=Hideo Tsunakawa| volume = 6 | issue = 19 | pages = eaba1050 | doi=10.1126/sciadv.aba1050 | pmid = 32494721 | pmc = 7202878 | bibcode = 2020SciA....6.1050Y |issn = 2375-2548 |doi-access=free }}</ref>
* The iron oxide (FeO) content (13%) of the Moon, intermediate between that of Mars (18%) and the terrestrial mantle (8%), rules out most of the source of the proto-lunar material from Earth's mantle.<ref name=taylor07/>
* If the bulk of the proto-lunar material had come from an impactor, the Moon should be enriched in [[Siderophile element|siderophilic]] elements, when, in fact, it is deficient in them.<ref name=jess114/>
* The Moon's oxygen isotopic ratios are essentially identical to those of Earth.<ref name=wiechert/> Oxygen isotopic ratios, which may be measured very precisely, yield a unique and distinct signature for each Solar System body.<ref name=scott010312/> If a separate proto-planet [[Theia (planet)|Theia]] had existed, it probably would have had a different oxygen isotopic signature than Earth, as would the ejected mixed material.<ref name=moonwalk/>
* The Moon's [[titanium isotope]] ratio (<sup>50</sup>Ti/<sup>47</sup>Ti) appears so close to Earth's (within 4 ppm), that little if any of the colliding body's mass could likely have been part of the Moon.<ref>{{cite journal | title = The proto-Earth as a significant source of lunar material | journal = Nature Geoscience | date = 25 March 2012 | first = Junjun | last = Zhang |author2=Nicolas Dauphas |author3=Andrew M. Davis |author4=Ingo Leya |author5=Alexei Fedkin | volume = 5 | issue = 4 | pages = 251–255| doi= 10.1038/ngeo1429 |bibcode = 2012NatGe...5..251Z }}</ref><ref>{{cite web | url=https://news.uchicago.edu/article/2012/03/28/titanium-paternity-test-fingers-earth-moon-s-sole-parent | title=Titanium paternity test fingers Earth as moon's sole parent | work=UChicagoNews | date=March 28, 2012 | access-date=August 13, 2012 | last=Koppes |first=Steve}}</ref>