Editing Xenon (section)

=== Cosmic processes ===
Because xenon is a tracer for two parent isotopes, xenon isotope ratios in [[meteorite]]s are a powerful tool for studying the [[formation of the Solar System]]. The [[Iodine–xenon dating|iodine–xenon method]] of [[Radiometric dating|dating]] gives the time elapsed between [[nucleosynthesis]] and the condensation of a solid object from the [[solar nebula]]. In 1960, physicist [[John Reynolds (physicist)|John H. Reynolds]] discovered that certain [[meteorite]]s contained an isotopic anomaly in the form of an overabundance of xenon-129. He inferred that this was a [[decay product]] of radioactive [[iodine-129]]. This isotope is produced slowly by [[cosmic ray spallation]] and [[nuclear fission]], but is produced in quantity only in supernova explosions.<ref name="Clayton 1983 75">{{cite book
| first      = Donald D.
| last       = Clayton
| date       = 1983
| title      = Principles of Stellar Evolution and Nucleosynthesis
| page       = [https://archive.org/details/principlesofstel0000clay/page/75 75]
| edition    = 2nd
| url        = https://archive.org/details/principlesofstel0000clay
| url-access = registration
| publisher  = University of Chicago Press
| isbn       = 0-226-10953-4
}}</ref><ref name="Bolt, B. A. 2007">{{cite web
| author      = Bolt, B. A.
| author2     = Packard, R. E.
| author3     = Price, P. B.
| year        = 2007
| url         = http://content.cdlib.org/xtf/view?docId=hb1r29n709&doc.view=content&chunk.id=div00061&toc.depth=1&brand=oac&anchor.id=0
| title       = John H. Reynolds, Physics: Berkeley
| publisher   = [[The University of California, Berkeley]]
| access-date = October 1, 2007
}}</ref>

Because the half-life of <sup>129</sup>I is comparatively short on a cosmological time scale (16 million years), this demonstrated that only a short time had passed between the supernova and the time the meteorites had solidified and trapped the <sup>129</sup>I. These two events (supernova and solidification of gas cloud) were inferred to have happened during the early history of the [[Solar System]], because the <sup>129</sup>I isotope was likely generated shortly before the Solar System was formed, seeding the solar gas cloud with isotopes from a second source. This supernova source may also have caused collapse of the solar gas cloud.<ref name="Clayton 1983 75" /><ref name="Bolt, B. A. 2007" />

In a similar way, xenon isotopic ratios such as <sup>129</sup>Xe/<sup>130</sup>Xe and <sup>136</sup>Xe/<sup>130</sup>Xe are a powerful tool for understanding planetary differentiation and early outgassing.<ref name="kaneoka">{{cite journal
| last    = Kaneoka
| first   = Ichiro
| s2cid   = 128502357
| title   = Xenon's Inside Story
| journal = Science
| year    = 1998
| volume  = 280
| issue   = 5365
| pages   = 851–852
| doi     = 10.1126/science.280.5365.851b
}}</ref> For example, the [[atmosphere of Mars]] shows a xenon abundance similar to that of Earth (0.08&nbsp;parts per million<ref>{{cite web
| last         = Williams
| first        = David R.
| date         = September 1, 2004
| url          = http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html
| title        = Mars Fact Sheet
| publisher    = NASA
| access-date  = October 10, 2007
| archive-url  = https://web.archive.org/web/20100612092806/http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html
| archive-date = June 12, 2010
| url-status   = dead
}}</ref>) but Mars shows a greater abundance of <sup>129</sup>Xe than the Earth or the Sun. Since this isotope is generated by radioactive decay, the result may indicate that Mars lost most of its primordial atmosphere, possibly within the first 100 million years after the planet was formed.<ref>{{cite web
| last         = Schilling
| first        = James
| url          = http://humbabe.arc.nasa.gov/mgcm/HTML/FAQS/thin_atm.html
| title        = Why is the Martian atmosphere so thin and mainly carbon dioxide?
| publisher    = Mars Global Circulation Model Group
| access-date  = October 10, 2007
| url-status   = dead
| archive-url  = https://web.archive.org/web/20100528010109/http://humbabe.arc.nasa.gov/mgcm/HTML/FAQS/thin_atm.html
| archive-date = May 28, 2010
}}</ref><ref>{{cite journal
| last    = Zahnle
| first   = Kevin J.
| title   = Xenological constraints on the impact erosion of the early Martian atmosphere
| journal = [[Journal of Geophysical Research]]
| year    = 1993
| volume  = 98
| issue   = E6
| pages   = 10,899–10,913
| doi     = 10.1029/92JE02941
| bibcode = 1993JGR....9810899Z
| url     = https://zenodo.org/record/1231333
}}</ref> In another example, excess <sup>129</sup>Xe found in [[carbon dioxide]] well gases from [[New Mexico]] is believed to be from the decay of [[Mantle (geology)|mantle]]-derived gases from soon after Earth's formation.<ref name="caldwell" /><ref>{{cite journal
| last    = Boulos
| first   = M. S.
| author2 = Manuel, O.K.
| s2cid   = 28159702
| title   = The xenon record of extinct radioactivities in the Earth
| journal = [[Science (journal)|Science]]
| volume  = 174
| issue   = 4016
| pages   = 1334–6
| date    = 1971
| doi     = 10.1126/science.174.4016.1334
| pmid    = 17801897
| bibcode = 1971Sci...174.1334B
}}</ref>