Radiometric dating of surface rocks
The team performed a process known as uranium-lead dating on zircon samples that were extracted from the Apollo 14 space rocks.This required them to liquefy the zircon samples in acid, destroying the space rock artefacts.So instead of trying to find chunks of rock that had been there since the early days, the team instead turned to zircon - a mineral that would have formed as the Moon was cooling from its fresh, molten state into the rocky satellite we see today.Once formed, zircon crystals stay perfectly intact as little time signatures of geological events.Unfortunately, those methods don't work on all rocks, and they don't work at all if you don't have rocks in the laboratory to age-date. They are descriptions of how one rock or event is older or younger than another.
The simplest is the law of superposition: if thing A is deposited on top of (or cuts across, or obliterates) thing B, then thing B must have been there already when thing A happened, so thing B is older than thing A.In the science of geology, there are two main ways we use to describe how old a thing is or how long ago an event took place. When you say that I am 38 years old or that the dinosaurs died out 65 million years ago, or that the solar system formed 4.6 billion years ago, those are absolute ages.There are absolute ages and there are relative ages. We use a variety of laboratory techniques to figure out absolute ages of rocks, often having to do with the known rates of decay of radioactive elements into detectable daughter products.A few days ago, I wrote a post about the basins of the Moon -- a result of a trip down a rabbit hole of book research.Here's the next step in that journey: the Geologic Time Scales of Earth and the Moon.