Rubidium/Strontium Dating of MeteoritesThe study of the rubidium/strontium isotopic ratios in a set of meteorite samples shows the general approach to this kind of radioactive dating. The isotope ^{87}Rb decays into the ground state of ^{87}Sr with a halflife of 4.7 x 10^{10} years and a maximum b^{} energy of 272 keV. ^{86}Sr is of nonradiogenic origin and can be used as a reference concentration to imply the original concentration of ^{87}Sr. From an example by Jelley, the following five chondritic meteorites are reported to have the following proportions of the rubidium and strontium isotopes:
This data was plotted with the spreadsheet Excel as shown below. The age consistent with the slope of this plot can be calculated in a way which makes use of the nonradiogenic ^{86}Sr as a reference. The slope obtained was m=0.0676, using the pointslope form of a line, y = mx + b, and the corresponding age is 4.6 x 10^{9} years. The intercept b = 0.70 suggests that these values for isotopic abundances are consistent with an original strontium isotope ratio ^{87}Sr/ ^{86}Sr = 0.7 . While the consistency is remarkable, there are uncertainties. A glance at the plot above shows that the Homestead meteorite is a bit off the line with the others. In fact, if just an average of the pointtopoint slopes for all the data points is used, including the Homestead meteorite, an age of 4.7 billion is obtained, showing that there is a significant uncertainty in the dates obtained. The 4.6 billion year value was obtained by eliminating the Homestead meteorite, since that appeared to give a more consistent slope for the curve. This is all the data I have about these particular samples  comments about this scenario are invited. 
Index Reference Jelley Sec 3.8  

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