Editing Age of Earth (section)

====Canyon Diablo meteorite====
{{Further|Age of the Solar System|Canyon Diablo (meteorite)}}[[File:Barringer Crater aerial photo by USGS.jpg|thumb|upright|[[Meteor Crater|Barringer Crater]], Arizona, where the Canyon Diablo meteorite was found.]]

The [[Canyon Diablo (canyon)|Canyon Diablo]] meteorite was used because it is both large and representative of a particularly rare type of meteorite that contains [[sulfide]] minerals (particularly [[troilite]], FeS), metallic [[nickel]]-[[iron]] alloys, plus silicate minerals. This is important because the presence of the three mineral phases allows investigation of isotopic dates using samples that provide a great separation in concentrations between parent and daughter nuclides. This is particularly true of uranium and lead. Lead is strongly [[chalcophile|chalcophilic]] and is found in the sulfide at a much greater concentration than in the silicate, versus uranium. Because of this segregation in the parent and daughter nuclides during the formation of the meteorite, this allowed a much more precise date of the formation of the solar disk and hence the planets than ever before.

[[File:Canyon-diablo-meteorite.jpg|thumb|upright|left|Fragment of the Canyon Diablo iron meteorite.]]

The age determined from the Canyon Diablo meteorite has been confirmed by hundreds of other age determinations, from both terrestrial samples and other meteorites.<ref>{{cite conference
 | author=Terada, K.| author2=Sano, Y.
 | title=In-situ ion microprobe U-Pb dating of phosphates in H-chondrites | book-title=Proceedings, Eleventh Annual V. M. Goldschmidt Conference
 | publisher=Lunar and Planetary Institute
 | date=May 20–24, 2001
 | location=Hot Springs, Virginia | url=http://www.lpi.usra.edu/meetings/gold2001/pdf/3306.pdf | access-date=2008-12-22
 | bibcode=2001eag..conf.3306T | archive-url= https://web.archive.org/web/20081216214310/http://www.lpi.usra.edu/meetings/gold2001/pdf/3306.pdf| archive-date= 16 December 2008 | url-status= live}}</ref> The meteorite samples, however, show a spread from 4.53 to 4.58 billion years ago. This is interpreted as the duration of formation of the solar nebula and its collapse into the solar disk to form the Sun and the planets. This 50 million year time span allows for accretion of the planets from the original solar dust and meteorites.

The Moon, as another extraterrestrial body that has not undergone plate tectonics and that has no atmosphere, provides quite precise age dates from the samples returned from the Apollo missions. Rocks returned from the Moon have been dated at a maximum of 4.51 billion years old. [[Martian meteorites]] that have landed upon Earth have also been dated to around 4.5 billion years old by [[lead–lead dating]]. Lunar samples, since they have not been disturbed by weathering, plate tectonics or material moved by organisms, can also provide dating by direct [[electron microscope]] examination of [[cosmic ray]] tracks. The accumulation of dislocations generated by high energy cosmic ray particle impacts provides another confirmation of the isotopic dates. [[Environmental radioactivity#Activation products from cosmic rays|Cosmic ray dating]] is only useful on material that has not been melted, since melting erases the crystalline structure of the material, and wipes away the tracks left by the particles.