Dating rocks from the moon

One possibility is that the young ages reflect impact events, not the original time of igneous crystallization.

Long before I understood what any of it meant, I'd daydream in science class, staring at this chart, sounding out the names, wondering what those black-and-white bars meant, wondering what the colors meant, wondering why the divisions were so uneven, knowing it represented some kind of deep, meaningful, systematic organization of scientific knowledge, and hoping I'd have it all figured out one day.

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.

Researchers are developing instruments and methods for measuring the ages of rocks encountered during space missions to the Moon or other planets. Scott Anderson has now demonstrated that this technique can successfully date an Earth rock -- the Duluth Gabbro -- that is analogous to the rocks that cover one-third of the lunar nearside.

Many of the techniques used to date rocks on Earth are not practical in spaceflight, but a technique called laser ablation resonance ionization mass spectrometry can avoid the need for sophisticated sample preparation. Their results, published in Rapid Communications in Mass Spectrometry, imply that events from Solar System history that are recorded on much of the visible face of the Moon can one day be dated directly by instruments aboard a lunar lander.

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