...the who's who,
and the what's what 
of the space industry

news Space News

Search News Archive

Title

Article text

Keyword

  • Home
  • News
  • 'Slushy' magma ocean led to formation of the Moon's crust

'Slushy' magma ocean led to formation of the Moon's crust

Written by  Friday, 14 January 2022 05:26
Write a comment
Cambridge UK (SPX) Jan 14, 2022
Scientists have shown how the freezing of a 'slushy' ocean of magma may be responsible for the composition of the Moon's crust. The scientists, from the University of Cambridge and the Ecole normale superieure de Lyon, 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.

Scientists have shown how the freezing of a 'slushy' ocean of magma may be responsible for the composition of the Moon's crust.

The scientists, from the University of Cambridge and the Ecole normale superieure de Lyon, 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 the journal Geophysical Research Letters.

Over fifty years ago, Apollo 11 astronauts collected samples from the lunar Highlands. These large, pale regions of the Moon - visible to the naked eye - are made up of relatively light rocks called anorthosites. Anorthosites formed early in the history of the Moon, between 4.3 and 4.5 billion years ago.

Similar anorthosites, formed through the crystallisation of magma, can be found in fossilised magma chambers on Earth. Producing the large volumes of anorthosite found on the Moon, however, would have required a huge global magma ocean.

Scientists believe that the Moon formed when two protoplanets, or embryonic worlds, collided. The larger of these two protoplanets became the Earth, and the smaller became the Moon. One of the outcomes of this collision was that the Moon was very hot - so hot that its entire mantle was molten magma, or a magma ocean.

"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," said co-author Chloe Michaut from Ecole normale superieure de Lyon. "This 'flotation' model explains how the lunar Highlands may have formed."

However, since the Apollo missions, many lunar meteorites have been analysed and the surface of the Moon has been extensively studied. Lunar anorthosites appear more heterogeneous in their composition than the original Apollo samples, which contradicts a flotation scenario where the liquid ocean is the common source of all anorthosites.

The range of anorthosite ages - over 200 million years - is difficult to reconcile with an ocean of essentially liquid magma whose characteristic solidification time is close to 100 million years.

"Given the range of ages and compositions of the anorthosites on the Moon, and what we know about how crystals settle in solidifying magma, the lunar crust must have formed through some other mechanism," said co-author Professor Jerome Neufeld from Cambridge's Department of Applied Mathematics and Theoretical Physics.

Michaut and Neufeld developed a mathematical model to identify this mechanism.

In the low lunar gravity, the settling of crystal is difficult, particularly when strongly stirred by the convecting magma ocean. If the crystals remain suspended as a crystal slurry, then when the crystal content of the slurry exceeds a critical threshold, the slurry becomes thick and sticky, and the deformation slow.

This increase of crystal content occurs most dramatically near the surface, where the slushy magma ocean is cooled, resulting in a hot, well-mixed slushy interior and a slow-moving, crystal-rich lunar 'lid'.

"We believe it's in this stagnant 'lid' that the lunar crust formed, as lightweight, anorthite-enriched melt percolated up from the convecting crystalline slurry below," said Neufeld. "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."

Enriched lunar surface rocks likely formed in magma chambers within the lid, which explains their diversity. The results suggest that the timescale of lunar crust formation is several hundreds of million years, which corresponds to the observed ages of the lunar anorthosites.

Serial magmatism was initially proposed as a possible mechanism for the formation of lunar anorthosites, but the slushy model ultimately reconciles this idea with that of a global lunar magma ocean.?

The research was supported by the European Research Council.

Jerome Neufeld is also affiliated with the Department of Earth Sciences. He is a Fellow of Trinity College.


Related Links
University of Cambridge
Mars News and Information at MarsDaily.com
Lunar Dreams and more

Tweet

Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once

credit card or paypal

SpaceDaily Monthly Supporter
$5 Billed Monthly

paypal only



MOON DAILY
Chang'E-5 Lander Makes First Onsite Detection of Water on Moon
Beijing, China (SPX) Jan 12, 2022
A joint research team led by Profs. LIN Yangting and LIN Honglei from the Institute of Geology and Geophysics of the Chinese Academy of Sciences (IGGCAS) observed water signals in reflectance spectral data from the lunar surface acquired by the Chang'E-5 lander, providing the first evidence of in-situ detection of water on the Moon. Researchers from the National Space Science Center of CAS, the University of Hawai'i at Manoa, the Shanghai Institute of Technical Physics of CAS and Nanjing Universit ... read more


Read more from original source...

You must login to post a comment.
Loading comment... The comment will be refreshed after 00:00.

Be the first to comment.

CONTACT THE AUTHOR

* Denotes Required Field
Personal information
Message

Interested in Space?

Hit the buttons below to follow us...