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Conference Paper: 26Al decay: Heat production and a revised age for Iapetus

Title26Al decay: Heat production and a revised age for Iapetus
Authors
KeywordsCosmochemistry
Geophysics
Issue Date2009
PublisherAcademic Press. The Journal's web site is located at http://www.elsevier.com/locate/icarus
Citation
Icarus, 2009, v. 204 n. 2, p. 658-662 How to Cite?
AbstractWe revisit the appropriate energies to be used for computing heat production from 26Al decay. Due to the complexity of the decay scheme of this radioisotope, previous geophysical studies have used values ranging from 1.2 to 4 MeV per decay. The upper bound corresponds to the difference in mass energy between the 26Al and 26Mg ground states. This includes energy carried away by neutrinos, which does not contribute to heating planetary material. The lower bound does not account for the heating caused by the absorption of the γ rays from the excited 26Mg, or for the annihilation energy deposited in the material if the decay occurs inside even small planetesimals. Based on the calculations described by Schramm et al. [Schramm, D., Tera, F., Wasserburg, G.J., 1970. The isotopic abundance of 26Mg and limits on 26Al in the early Solar System. Earth Planet. Sci. Lett. 10, 44-59] updated with the most recent nuclear constants, we recommend using a heat production value of 3.12 MeV per decay, which is the total energy of disintegration minus the energy carried off by the neutrinos. This heat production value is higher than the value used in the modeling of Iapetus by Castillo-Rogez et al. [Castillo-Rogez, J., Matson, D.L., Sotin, C., Johnson, T.V., Lunine, J.I., Thomas, P.C., 2007. Iapetus' geophysics: Rotation rate, shape, and equatorial ridge. Icarus 190, 179-202] by about a factor 2.5. The resulting estimate of the time of formation of Iapetus is shifted by about 1 Myr, to between ∼3.4 and 5.4 Myr after the production of the calcium-aluminum inclusions (CAIs). © 2009 Elsevier Inc.
Persistent Identifierhttp://hdl.handle.net/10722/64145
ISSN
2015 Impact Factor: 3.383
2015 SCImago Journal Rankings: 2.447
ISI Accession Number ID
Funding AgencyGrant Number
Government sponsorship
JPL Research and Technology Development program
NASA
Hong Kong RGCHKU 7024/08P
Funding Information:

The authors are grateful to Dimitri Papanastassiou (JPL) for recommending use of the study by Schramm et al. (1970). The authors also thank William McKinnon and GJ. Wasserburg for their reviews, which contributed to improve the clarity of this article. This work has been conducted at the jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2008 California Institute of Technology. Government sponsorship acknowledged. JCCR acknowledges support of the JPL Research and Technology Development program, NJT the support of the NASA Outer Planets Research Program, and MHL the support of Hong Kong RGC Grant HKU 7024/08P.

References

 

DC FieldValueLanguage
dc.contributor.authorCastilloRogez, Jen_HK
dc.contributor.authorJohnson, TVen_HK
dc.contributor.authorLee, MHen_HK
dc.contributor.authorTurner, NJen_HK
dc.contributor.authorMatson, DLen_HK
dc.contributor.authorLunine, Jen_HK
dc.date.accessioned2010-07-13T04:41:24Z-
dc.date.available2010-07-13T04:41:24Z-
dc.date.issued2009en_HK
dc.identifier.citationIcarus, 2009, v. 204 n. 2, p. 658-662en_HK
dc.identifier.issn0019-1035en_HK
dc.identifier.urihttp://hdl.handle.net/10722/64145-
dc.description.abstractWe revisit the appropriate energies to be used for computing heat production from 26Al decay. Due to the complexity of the decay scheme of this radioisotope, previous geophysical studies have used values ranging from 1.2 to 4 MeV per decay. The upper bound corresponds to the difference in mass energy between the 26Al and 26Mg ground states. This includes energy carried away by neutrinos, which does not contribute to heating planetary material. The lower bound does not account for the heating caused by the absorption of the γ rays from the excited 26Mg, or for the annihilation energy deposited in the material if the decay occurs inside even small planetesimals. Based on the calculations described by Schramm et al. [Schramm, D., Tera, F., Wasserburg, G.J., 1970. The isotopic abundance of 26Mg and limits on 26Al in the early Solar System. Earth Planet. Sci. Lett. 10, 44-59] updated with the most recent nuclear constants, we recommend using a heat production value of 3.12 MeV per decay, which is the total energy of disintegration minus the energy carried off by the neutrinos. This heat production value is higher than the value used in the modeling of Iapetus by Castillo-Rogez et al. [Castillo-Rogez, J., Matson, D.L., Sotin, C., Johnson, T.V., Lunine, J.I., Thomas, P.C., 2007. Iapetus' geophysics: Rotation rate, shape, and equatorial ridge. Icarus 190, 179-202] by about a factor 2.5. The resulting estimate of the time of formation of Iapetus is shifted by about 1 Myr, to between ∼3.4 and 5.4 Myr after the production of the calcium-aluminum inclusions (CAIs). © 2009 Elsevier Inc.en_HK
dc.languageengen_HK
dc.publisherAcademic Press. The Journal's web site is located at http://www.elsevier.com/locate/icarusen_HK
dc.relation.ispartofIcarusen_HK
dc.subjectCosmochemistryen_HK
dc.subjectGeophysicsen_HK
dc.title26Al decay: Heat production and a revised age for Iapetusen_HK
dc.typeConference_Paperen_HK
dc.identifier.emailLee, MH:mhlee@hku.hken_HK
dc.identifier.authorityLee, MH=rp00724en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1016/j.icarus.2009.07.025en_HK
dc.identifier.scopuseid_2-s2.0-70350382726en_HK
dc.identifier.hkuros167374en_HK
dc.identifier.hkuros177714-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-70350382726&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume204en_HK
dc.identifier.issue2en_HK
dc.identifier.spage658en_HK
dc.identifier.epage662en_HK
dc.identifier.isiWOS:000271738500025-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridCastilloRogez, J=18435894000en_HK
dc.identifier.scopusauthoridJohnson, TV=7404019423en_HK
dc.identifier.scopusauthoridLee, MH=7409119699en_HK
dc.identifier.scopusauthoridTurner, NJ=7202572880en_HK
dc.identifier.scopusauthoridMatson, DL=35417546500en_HK
dc.identifier.scopusauthoridLunine, J=7005182766en_HK
dc.identifier.citeulike5347323-

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