Studying hafnium and tungsten on the Moon are particularly important because they constitute a natural radioactive clock
of the isotope hafnium-182 decaying into tungsten-182.
The method assumes that uranium was taken up just once in the past and then decayed giving us a radioactive clock
but this is probably not the case in reality.
The researchers also dated the Sudbury rocks using the samarium-neodymium radioactive clock
to obtain an age of 1.8 billion years -- in excellent agreement with previous dating using uranium and lead isotopes.
(23) The forces suggested by the meteor impact that killed off the dinosaurs were orders of magnitude greater than what occurred in Thailand and neighboring countries, and yet there do not seem to be any studies on how this could have reset all the radioactive clocks
. Very extensive hydrothermal effects were also a likely outcome of the meteorite impact.