Thursday, March 28, 2024
News

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

   SocialTwist Tell-a-Friend    Print this Page   COMMENT

Cambridge | January 25, 2022 11:20:20 AM IST
Earth's natural satellite Moon, has always been a subject of immense suspense and has shown ample room for discovery. Now, 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 were reported in the journal 'Geophysical Review 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 -- were 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, are also 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 believed 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 appeared more heterogenous 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 occured 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 explained their diversity. The results suggested that the timescale of lunar crust formation is several hundreds of million years, which corresponded 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. (ANI)

 
  LATEST COMMENTS ()
POST YOUR COMMENT
Comments Not Available
 
POST YOUR COMMENT
 
 
TRENDING TOPICS
 
 
CITY NEWS
MORE CITIES
 
 
 
MORE SCIENCE NEWS
Researchers discover new approach to tre...
Researchers discover how gene mutation r...
Climate change disrupts vital ecosystems...
Study finds how ageing reduces ability o...
Israeli researchers uncover biological p...
Nanotechnology breakthrough in Israel co...
More...
 
INDIA WORLD ASIA
NET score allowed for admissions to PhD ...
'Don't have that kind of money to contes...
'Congress will win all 6 seats in by-ele...
'There is a huge wave for PM Modi in Tam...
Congress releases list of 16 candidate f...
Vijay Shivtare meets Maharashtra CM and ...
More...    
 
 Top Stories
HCG Puts its Patients First Again w... 
Vantage Markets extends its competi... 
Taiwan detects 20 Chinese military ... 
Florence Pugh shares BTS moments fr... 
Israel and cyprus move forward on u... 
Manhunt for terrorist after 3 Israe... 
Kyle Richards recalls "amazing" adv... 
"Trained on roads....": Racewalk at...