A New Timeline Established Of Moon Formation

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08/18/2011 08:55 AM ET

Due to developments in scientific concepts, a new timeline has been established of the Moon’s formation, and it is believed that it was created when a Mars like object collided with Earth.

However, research shows that the timeline of that creation may not be as long ago as first thought. On the Moon, a group of rocks called ferroan anorthosites (or FANs) are thought to have accumulated atop the magma ocean as they crystallized, forming the lunar crust. FANs have proven very difficult to date because of the poorly constrained isotopic geochemistry of the oldest moon rocks.

As a result, their calculated ages have had rather large error bars attached to them.

The authors of the new research were able to develop improved methods for dating FANs. That allowed them to calculate ages with unprecedented precision using three isotopic systems commonly applied to these rocks. For the first time, the researchers calculated a concordant age that is, an age on which these different series agree exactly.

Previous attempts to date FANs had encountered too much error for the series to agree so precisely.

The work resulted in an age of 4.36 billion years (give or take 3 million). That’s several tens of millions of years more recent than we had thought the Moon’s crust formed. This leads to one of two possibilities: either the Moon took much longer to accrete and solidify than we thought, or the assumptions about FANs forming in the last stages of magma oceans are incorrect.

A different process (known as serial magmatism) could explain the measured FAN ages, but the magma ocean theory was partly based on the characteristics of FANs.

If FANs are a product of a different process, our understanding of how planetary bodies solidify and differentiate could take a step backward.

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