The violent birth of the moon: New theory ‘reinvents’ lunar origin
How the moon was born as a donut: New theory says Earth’s satellite emerged from a spinning ring of vaporized Earth’s rock
- Scientists have long been working to understand how the moon really formed
- The Apollo missions revealed its chemical composition is much like Earth’s
- A new theory could finally explain how this came to be, by proposing a ‘synestia’
- Donut-shaped object of spinning molten and vaporized rock forms after collision
- Researchers now say the moon may have been born inside such an object
A new hypothesis on the birth of the moon could finally help to solve longstanding questions about its chemical makeup, and explain why it’s similar to Earth in so many ways.
Prior to the Apollo missions, it was thought that the moon is composed primarily of materials from the cosmic object that slammed into a young Earth billions of years ago.
Samples gathered during the moon landings, however, showed that this is not the case; instead, scientists discovered that chemically, it’s nearly Earth’s twin.
The new explanation proposed by physicist Sarah Stewart aims to solve this mystery by considering that proto-Earth may have been spinning much faster than previously considered, resulting in a donut-like mass of vaporized rock after the collision.
As this cosmic donut cooled, the magma rain that formed in its outer edges clumped together to become what would eventually be the moon – meaning it was essentially born ‘inside the vaporized Earth,’ according to the researcher.
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The new explanation proposed by physicist Sarah Stewart aims to solve this mystery by considering that proto-Earth may have been spinning much faster than previously considered, resulting in a donut-like mass of vaporized rock after the collision (illustrated above)
The new moon origin explanation has won Stewart the MacArthur Foundation Fellowship, or the ‘genius grant,’ with a $625,000 award, according to Nautilus.
‘The new work explains features of the moon that are hard to resolve with current ideas,’ Stewart, professor of earth and planetary sciences at the University of California, Davis, explained earlier this year.
‘The moon is chemically almost the same as the Earth, but with some differences. This is the first model that can match the pattern of the moon’s composition.’
In the new model developed by the team from UC Davis and Harvard University, the origin of the moon relies on a newly-proposed object known as a synestia.
Their findings are published in the Journal of Geophysical Research.
These short-lived objects are created when planted-sized bodies collide, causing the molten and vaporized rock to spin rapidly around part of the body, which lies in the center.
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In the new model, the origin of the moon relies on a newly-proposed object known as a synestia. These short-lived objects are created when planted-sized bodies collide (A and B), resulting in a donut-shaped mass of molten and vaporized rock (C)
According to the researchers, synestias only stick around for a few hundred years before shrinking down as they cool, ultimately forming a molten planet.
‘Our model starts with a collision that forms a synestia,’ said Harvard graduate student Simon Lock, lead author on the study.
‘The moon forms inside the vaporized Earth at temperatures of four to six thousand degrees Fahrenheit and pressures of tens of atmospheres.’
The new model also means there is more wiggle room in the conditions for the moon’s formation, the researchers say.
According to Lock, a synestia like the one needed in this lunar origin scenario can be created in numerous ways.
As this cosmic donut cooled, the magma rain that formed in its outer edges clumped together to become what would eventually be the moon – meaning it was essentially born ‘inside the vaporized Earth.’ This process is illustrated in the graphic above
WHAT ARE THE THEORIES ON THE ORIGIN OF THE MOON?
Many researchers believe the moon formed after Earth was hit by a planet the size of Mars billions of years ago.
This is called the giant impact hypothesis.
The theory suggests the moon is made up of debris left over following a collision between our planet and a body around 4.5 billion years ago.
The colliding body is sometimes called Theia, after the mythical Greek Titan who was the mother of Selene, the goddess of the moon.
Many researchers believe the moon formed after Earth was hit by a planet the size of Mars billions of years ago. This is called the giant impact hypothesis
But one mystery has persisted, revealed by rocks the Apollo astronauts brought back from the moon: Why are the moon and Earth so similar in their composition?
Several different theories have emerged over the years to explain the similar fingerprints of Earth and the moon.
Perhaps the impact created a huge cloud of debris that mixed thoroughly with the Earth and then later condensed to form the moon.
Or Theia could have, coincidentally, been chemically similar to young Earth.
A third possibility is that the moon formed from Earthen materials, rather than from Theia, although this would have been a very unusual type of impact.
And, these objects are likely created frequently during rocky planet formation, Stewart told Nautilus.
The new synestia hypothesis turns the decades-old ‘giant impact’ theory on its head. But, as the researchers point out, the evidence shows we were well overdue for a new model that hasn’t been disproven.
‘The Apollo mission found that the moon is practically a twin of the Earth, particularly its mantle, in major elements and in isotopic ratios,’ Stewart told Nautilus.
‘The different weight elements are like fingerprints, present in the same abundances. Every single small asteroid and planet in the solar system has a different fingerprint, except the Earth and the moon.
‘So the giant impact hypothesis was wrong.’
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