10
Timing
of the Assembly Process?
Over time inside 87Rb one n®p+ so 87Rb ® 87Sr
•Use relative amounts of Rb, Sr to determine age of
rocks
•Half life:
Time it takes ½ of “parent” to decay to
“daughter”
•Other unstable elements: 40K
235U 238U
•Ages of old surfaces and meteorites: ~4.5 billion years
From “How to Build a
Habitable Planet”
by Broecker
by Broecker
From our text: Horizons by Seeds