The Moon: bright, milky white and 40 million years older than we thought

The Moon is at least 4.46 billion years old according to new analysis of crystals collected from the lunar surface in 1972.

When astronauts from Apollo 17 landed on the Moon, they collected dust containing tiny crystals, which they brought back to Earth.

Analysis of those crystals published in Geochemical Perspectives Letters reveals the Moon is at least 40 million years older than previously thought.

The Moon was formed more than 4 billion years ago, after a giant object – about the size of Mars – crashed into the Earth, breaking a piece off and melting it. 

Author and professor Philipp Heck from the University of Chicago and the Field Museum’s Robert A. Pritzker Curator for Meteoritics and Polar Studies, says by dating the crystals – thought to have formed after the impact – scientists can estimate the minimum possible age of the Moon.    

“When the surface was molten like that, zircon crystals couldn’t form and survive. So any crystals on the Moon’s surface must have formed after this lunar magma ocean cooled,” he says.

While previous studies have suggested the Moon’s age, the paper uses a new method called atom probe tomography and radiometric dating, to analyse atoms inside the zircon crystals, and their level of radioactive decay to estimate age.

The age of the crystals suggest the Moon is at least 4.46 billion years old.