Cambridge scientists work out how Moon crust was formed

Magma ocean on the Moon - NASA/Goddard Space Flight Center
Magma ocean on the Moon Credit: NASA/Goddard Space Flight Center

Scientists in Cambridge have demonstrated the Moon's crust may have been formed similar to crystals in a slushy machine.

The researchers demonstrated that the freezing of a sea of molten rock - or magma - could have lead to the formation of its surface.

That is according to a new theory from academics at the University of Cambridge and the Ecole normale supérieure de Lyon.

They have proposed a new model of crystallisation, where crystals remained suspended in liquid magma over hundreds of millions of years as the lunar ‘slush’ froze and solidified.

The results are reported in "Formation of the Lunar Primary Crust From a Long-Lived Slushy Magma Ocean" in the journal Geophysical Research Letters.

The study, supported by the European Research Council, is based on samples collected by Neil Armstrong and Buzz Aldrin during the Moon landings in 1969.

They collected samples from the lunar Highlands, they were made up of relatively light rocks called anorthosites which were between 4.3 and 4.5 billion years old.

Similar rocks can be found in fossilised magma chambers on Earth.

Scientists believe that the Moon formed when two planetary objects collided. One would become the Earth, the other the Moon.

The result of the impact was the Moon was covered by a magma ocean.

Chloé Michaut from Ecole normale supérieure de Lyon, who co-authored the paper explained:

“Since the Apollo era, it has been thought that the lunar crust was formed by light anorthite crystals floating at the surface of the liquid magma ocean, with heavier crystals solidifying at the ocean floor.

“This ‘flotation’ model explains how the lunar Highlands may have formed.”

But further studies of lunar samples have shown that the anorthosites appear more diverse than the original Apollo samples, which contradicts earlier theories as to how the crust was formed.

Professor Jerome Neufeld from Cambridge’s Department of Applied Mathematics and Theoretical Physics worked with Michaut to develop a mathematical model to identify this mechanism.

“We suggest that cooling of the early magma ocean drove such vigorous convection that crystals remained suspended as a slurry, much like the crystals in a slushy machine.”

The news comes amid renewed interest in a return to the Moon. Scientists from The Open University are supporting NASA's bid for more lunar landings.

The announcement comes on the eve of the 50th anniversary of the first Moon landings on July 20th 1969.

The OU has teamed with NASA Goddard Spaceflight Centre (alongside the European Space Agency) to build an instrument which will monitor the very thin atmosphere near the surface of the Moon as part of NASA’s Artemis programme.

Artemis is a long term project designed to create a habitable moonbase. It is hoped it will eventually become a staging post for manned missions to Mars.

In 2019 the Chinese space agency landed a rover on the moon's surface. It produced video of the far side of the moon. The pictures showed the Jade Rabbit 2 rover and the Chang'e 4 spacecraft that transported it on the first soft landing on the far side of the moon, which always faces away from Earth.