1. A Complication in Determining the Precise Age of the Solar System Dating early Solar System events by the Pb-Pb method can resolve absolute age differences of ~1 My The technique traditionally assumes that 238 U/ 235 U is uniform in Solar System materials for any given time Recent results indicate that this is not always the case http://www.psrd.hawaii.edu/Jan10/Curium-247.html

2. A Complication in Determining the Precise Age of the Solar System The excess 235 U is likely caused by the decay of 247 Cm, an extinct isotope (half life of 15.7 My) Th and Nd behave geo- chemically like Cm, so are surrogates of it: The more Th and Nd, the more Cm The correlation of 235 U/ 238 U with Th/U and Nd/U suggests the presence of 247 Cm http://www.psrd.hawaii.edu/Jan10/Curium-247.html

3. A Complication in Determining the Precise Age of the Solar System http://www.psrd.hawaii.edu/Jan10/Curium-247.html Incorrect assumption about 238 U/ 235 U could cause an error in the age of ancient materials of up to 5 million years. Solution: Always measure both U and Pb isotopes. (From Brennecka, G. A., et al., 2010, Science, v. 327(5964), p. 449-451.)