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No evidence for a decrease of nuclear decay rates with increasing heliocentric distance based on radiochronology of meteorites

Meier, Matthias LU and Wieler, Rainer (2014) In Astroparticle Physics 55. p.63-75
Abstract
It has been argued that the decay rates of several radioactive nuclides are slightly lower at Earth's aphelion than at perihelion, and that this effect might depend on heliocentric distance. It might then be expected that nuclear decay rates be considerably lower at larger distances from the sun, e.g., in the asteroid belt at 2-3 AU from where most meteorites originate. If so, ages of meteorites obtained by analyses of radioactive nuclides and their stable daughter isotopes might be in error, since these ages are based on decay rates determined on Earth. Here we evaluate whether the large data base on nuclear cosmochronology offers any hint for discrepancies which might be due to radially variable decay rates. Chlorine-36 (t(1/2) = 301,000... (More)
It has been argued that the decay rates of several radioactive nuclides are slightly lower at Earth's aphelion than at perihelion, and that this effect might depend on heliocentric distance. It might then be expected that nuclear decay rates be considerably lower at larger distances from the sun, e.g., in the asteroid belt at 2-3 AU from where most meteorites originate. If so, ages of meteorites obtained by analyses of radioactive nuclides and their stable daughter isotopes might be in error, since these ages are based on decay rates determined on Earth. Here we evaluate whether the large data base on nuclear cosmochronology offers any hint for discrepancies which might be due to radially variable decay rates. Chlorine-36 (t(1/2) = 301,000 a) is produced in meteorites by interactions with cosmic rays and is the nuclide for which a decay rate dependence from heliocentric distance has been proposed, which, in principle, can be tested with our approach and the current data base. We show that compilations of Cl-36 concentrations measured in meteorites offer no support for a spatially variable Cl-36 decay rate. For very short-lived cosmic-ray produced radionuclides (half-lives < 10-100 days), the concentration should be different for meteorites hitting the Earth on the incoming vs. outgoing part of their orbit. However, the current data base of very short-lived radionuclides in freshly fallen meteorites is far from sufficient to deduce solid constraints. Constraints on the age of the Earth and the oldest meteorite phases obtained by the U-Pb dating technique give no hints for radially variable decay rates of the alpha-decaying nuclides U-235 or U-238. Similarly, some of the oldest phases in meteorites have U-Pb ages whose differences agree almost perfectly with respective age differences obtained with "short-lived" radionuclides present in the early solar system, again indicating no variability of uranium decay rates in different meteorite parent bodies in the asteroid belt. Moreover, the oldest U-Pb ages of meteorites agree with the main-sequence age of the sun derived from helioseismology within the formal similar to 1% uncertainty of the latter. Meteorite ages also provide no evidence for a decrease of decay rates with heliocentric distance for nuclides such as Rb-87 (decay mode beta(-) )K-40 (beta(-) and electron capture), and Sm-147 (alpha). 2014 Elsevier B.V. All rights reserved. (Less)
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organization
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Contribution to journal
publication status
published
subject
keywords
Nuclear decay rates, Meteorites, Radiochronology, Cosmogenic, radionuclides
in
Astroparticle Physics
volume
55
pages
63 - 75
publisher
Elsevier
external identifiers
  • wos:000335207700008
  • scopus:84896788867
ISSN
1873-2852
DOI
10.1016/j.astropartphys.2014.01.004
language
English
LU publication?
yes
id
2821abb4-008a-4ca1-b448-15211c262455 (old id 4487426)
date added to LUP
2014-06-23 15:14:44
date last changed
2017-03-26 03:07:54
@article{2821abb4-008a-4ca1-b448-15211c262455,
  abstract     = {It has been argued that the decay rates of several radioactive nuclides are slightly lower at Earth's aphelion than at perihelion, and that this effect might depend on heliocentric distance. It might then be expected that nuclear decay rates be considerably lower at larger distances from the sun, e.g., in the asteroid belt at 2-3 AU from where most meteorites originate. If so, ages of meteorites obtained by analyses of radioactive nuclides and their stable daughter isotopes might be in error, since these ages are based on decay rates determined on Earth. Here we evaluate whether the large data base on nuclear cosmochronology offers any hint for discrepancies which might be due to radially variable decay rates. Chlorine-36 (t(1/2) = 301,000 a) is produced in meteorites by interactions with cosmic rays and is the nuclide for which a decay rate dependence from heliocentric distance has been proposed, which, in principle, can be tested with our approach and the current data base. We show that compilations of Cl-36 concentrations measured in meteorites offer no support for a spatially variable Cl-36 decay rate. For very short-lived cosmic-ray produced radionuclides (half-lives &lt; 10-100 days), the concentration should be different for meteorites hitting the Earth on the incoming vs. outgoing part of their orbit. However, the current data base of very short-lived radionuclides in freshly fallen meteorites is far from sufficient to deduce solid constraints. Constraints on the age of the Earth and the oldest meteorite phases obtained by the U-Pb dating technique give no hints for radially variable decay rates of the alpha-decaying nuclides U-235 or U-238. Similarly, some of the oldest phases in meteorites have U-Pb ages whose differences agree almost perfectly with respective age differences obtained with "short-lived" radionuclides present in the early solar system, again indicating no variability of uranium decay rates in different meteorite parent bodies in the asteroid belt. Moreover, the oldest U-Pb ages of meteorites agree with the main-sequence age of the sun derived from helioseismology within the formal similar to 1% uncertainty of the latter. Meteorite ages also provide no evidence for a decrease of decay rates with heliocentric distance for nuclides such as Rb-87 (decay mode beta(-) )K-40 (beta(-) and electron capture), and Sm-147 (alpha). 2014 Elsevier B.V. All rights reserved.},
  author       = {Meier, Matthias and Wieler, Rainer},
  issn         = {1873-2852},
  keyword      = {Nuclear decay rates,Meteorites,Radiochronology,Cosmogenic,radionuclides},
  language     = {eng},
  pages        = {63--75},
  publisher    = {Elsevier},
  series       = {Astroparticle Physics},
  title        = {No evidence for a decrease of nuclear decay rates with increasing heliocentric distance based on radiochronology of meteorites},
  url          = {http://dx.doi.org/10.1016/j.astropartphys.2014.01.004},
  volume       = {55},
  year         = {2014},
}