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Why do
lava flows come out in mare basins?
•Mare
basins are the lowest areas of the planet
•The
crust beneath them is badly fractured by the impacts
•When
do the lavas come out?
–Superposition
only gives relative ages
–Can
use crater counts to estimate absolute ages – but need to know crater
rates
–Apollo
missions provided samples from which we have radioactive decay ages
From our text: Horizons by Seeds