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

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 geochemically 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

A Complication in Determining the
Precise Age of the Solar System
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.) http://www.psrd.hawaii.edu/Jan10/Curium-247.html