Russell, S. S. and Srinivasan, G. and Huss, G. R. and Wasserburg, G. J. and MacPherson, G. J. (1996) Evidence for Widespread ^(26)Al in the Solar Nebula and Constraints for Nebula Time Scales. Science, 273 (5276). pp. 757-762. ISSN 0036-8075. http://resolver.caltech.edu/CaltechAUTHORS:20131218-152816653
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A search was made for ^(26)Mg (^(26)Mg^*) from the decay of ^(26)Al (half-life = 0.73 million years) in Al-rich objects from unequilibrated ordinary chondrites. Two Ca-Al-rich inclusions (CAIs) and two Al-rich chondrules (not CAIs) were found that contained ^(26)Al when they formed. Internal isochrons for the CAIs yielded an initial ^(26)Al/^(27)Al ratio [(^(26)Al/^(27)Al)_0] of 5 x 10^(-5), indistinguishable from most CAIs in carbonaceous chondrites. This result shows that CAIs with this level of ^(26)Al are present throughout the classes of chondrites and strengthens the notion that ^(26)Al was widespread in the early solar system. The two Al-rich chondrules have lower ^(26)Mg^*, corresponding to a (^(26)Al/^(27)Al)_0 ratio of approximately 9 x 10^(-6). Five other Al-rich chondrules contain no resolvable ^(26)Mg^*. If chondrules and CAIs formed from an isotopically homogeneous reservoir, then the chondrules with ^(26)Al must have formed or been last altered approximately ~2 million years after CAIs formed; the ^(26)Mg^*-free chondrules formed >1 to 3 million years later still. Because ^(26)Mg^*-containing and ^(26)Mg^*-free chondrules are both found in Chainpur, which was not heated to more than approximately ~400ºC, it follows that parent body metamorphism cannot explain the absence of ^(26)Mg^* in some of these chondrules. Rather, its absence indicates that the lifetime of the solar nebula over which CAIs and chondrules formed extended over approximately ~5 million years.
|Additional Information:||© 1996 American Association for the Advancement of Science. Received 23 April 1996; accepted 17 July 1996. We thank A. M. Davis and an anonymous reviewer for comments that significantly improved this paper. This research was supported by NASA grants NAGW 3553 (G.J.M.) and NACW 3297 (G.J.W.). This is Caltech contribution no, 5679 (934).|
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|Official Citation:||Evidence for Widespread 26Al in the Solar Nebula and Constraints for Nebula Time Scales Russell SS, Srinivasan G, Huss GR, Wasserburg GJ, MacPherson GJ. Science. 1996 Aug 9;273(5276):757-62. PMID:8670407 [PubMed - as supplied by publisher|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||19 Dec 2013 00:00|
|Last Modified:||19 Dec 2013 00:49|
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