The moon’s crust may have formed from a ‘smobby’ magma ocean
The moon’s crust may have formed thanks to a “slushy” magma ocean that froze over hundreds of millions of years, a new study has revealed.
An international team of scientists, led by the University of Cambridge, created a series of computer and mathematical models to investigate the chemical composition and behavior of moon rocks, and how they would behave in the early “liquid magma” moon.
They found that as the moon cooled, after its initial explosive onset, the icy sea of molten rock could have led to the current lunar surface.
The moon’s crust may have formed similarly to crystals in a slushy machine, the researchers said, before being trapped in liquid magma for hundreds of millions of years as the young moon’s “slush” froze and solidified.
If the crystals remain suspended as a slurry, the slurry becomes thick and sticky when the crystal content of the slurry exceeds a critical threshold.
This increase in crystal content occurs most dramatically near the surface, where the muddy magma ocean is cooled, resulting in a hot, well-mixed muddy interior and a slow-moving, crystal-rich lunar “lid” — creating the lunar surface.
The moon’s crust may have formed thanks to a ‘slushy’ magma ocean that froze over hundreds of millions of years, a new study has revealed
An international team of scientists, led by the University of Cambridge in England, found that freezing a sea of molten rock could have led to the current lunar surface
SCIENTISTS DON’T AGREE ON HOW THE MOON FORMED
Many researchers believe that the moon formed after the Earth was hit by a planet the size of Mars billions of years ago.
This is called the giant impact hypothesis.
The theory suggests that the moon is made up of debris left over from a collision between our planet and a body about 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.
But one mystery has persisted, revealed by rocks brought by the Apollo astronauts from the moon: Why are the moon and Earth so similar in their composition?
Over the years, several theories have emerged to explain the similar fingerprints of the Earth and the Moon.
Perhaps the impact created a huge cloud of debris that thoroughly mixed with Earth and later condensed to form the moon.
Or Theia may, coincidentally, have been chemically similar to the young Earth.
A third possibility is that the moon was formed from earthen material, rather than from Theia, although this would have been a very unusual type of impact.
They used the composition of moon rocks returned to Earth by Neil Armstrong and Buzz Aldrin on July 24, 1969, as part of the Apollo 11 mission.
They come from the Lunar Highlands, a large pale region of the moon visible to the naked eye, and made of relatively light rocks called anorthosites, which were formed between 4.3 and 4.5 billion years ago – when the Moon was very young.
Previous studies suggested that these light anorthite crystals floated to the surface of the liquid magma ocean, with heavier crystals solidifying as the ocean floor.
However, later rock samples, from follow-up missions on the moon, revealed that the crystals were more diverse, contradicting this drift theory.
For this new study, the team, including Cambridge professor Jerome Neufeld, proposed a new crystallization model.
In their model, the crystals floated in liquid magma for hundreds of millions of years as the moon’s “slush” froze and solidified.
In the low lunar gravity, crystal settling is difficult, especially when it is strongly moved by the convective magma ocean.
“We believe it is in this stagnant ‘lid’ that the lunar crust formed, as lightweight, anorthite-enriched melt seeped upward from the convective crystalline slurry below,” said Professor Neufeld.
“We suggest that cooling of the early magma ocean caused such strong convection that crystals were suspended as a suspension, much like the crystals in a muddy machine.”
Enriched rocks on the lunar surface likely formed in magma chambers in the lid, explaining their diversity, the researchers added.
The results suggest that the timescale of lunar crust formation is several hundred million years, which corresponds to the observed ages of the lunar anorthosites.
Similar anorthosites, formed by the crystallization of magma, are found in fossilized magma chambers on Earth.
However, producing the large amounts of anorthosite found on the moon would have required a massive global magma ocean.
Scientists believe that the moon formed when two protoplanets or embryonic worlds collided.
The larger of these two protoplanets became Earth and the smaller became the Moon. One of the results of this collision was that the moon was very hot — so hot that the entire mantle was molten magma, or a magma ocean.
They found that the moon’s crust may have formed similar to crystals found in a muddy machine, where the crystals remain suspended in liquid magma for hundreds of millions of years as the young moon’s ‘slush’ froze and solidified.
“Since the Apollo era, the lunar crust was thought to be formed by light anorthite crystals floating on the surface of the liquid magma ocean, with heavier crystals congealing on the ocean floor,” said study co-author Chloé Michaut of Ecole Normale Supérieure de Lyon. .
“This ‘flotation’ model explains how the moon’s highlands were formed.”
However, since the Apollo missions, many lunar meteorites have been analyzed and the surface of the moon has been extensively studied.
“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 by a different mechanism,” said study co-author Professor Neufeld.
The findings are published in the journal Geophysical Survey Letters.
WHAT WAS THE APOLLO PROGRAM?
NASA photo taken on July 16, 1969 shows the huge, 363-foot-tall Apollo 11 Spacecraft 107/Lunar Module S/Saturn 506) spacecraft launched from Pad A, Launch Complex 39. Kennedy Space Center (KSC), at 9:32 a.m. ( EDT).
Apollo was the NASA program that launched in 1961 and got the first man on the moon eight years later.
The first four flights tested the equipment for the Apollo program and six of the other seven flights managed to land on the moon.
The first manned mission to the moon was Apollo 8, which circled it on Christmas Eve in 1968, but did not land.
The crew of Apollo 9 spent ten days in orbit, completing the first manned flight of the lunar module — the part of the Apollo rocket that would later land Neil Armstrong on the moon.
The Apollo 11 mission was the first to land on the moon on July 20, 1969.
The capsule landed on the Sea of Tranquility, with mission commander Neil Armstrong and pilot Buzz Aldrin aboard.
Armstrong and Aldrin walked on the lunar surface while Michael Collins remained in orbit around the moon.
When Armstrong became the first person to walk on the moon, he said, “That’s one small step for (a) man; a great leap for humanity.’
Apollo 12 landed on the Ocean of Storms later that year on November 19, writes NASA.
Apollo 13 was supposed to be the third mission to land on the moon, but just under 56 hours into the flight, an oxygen tank explosion forced the crew to cancel the moon landing and return to the Aquarius lunar module to return to the earth.
Apollo 15 was the ninth manned lunar mission in the Apollo space program and at the time was considered the most successful manned spaceflight to date due to its long duration and greater emphasis on scientific exploration than had been possible on previous missions.
The last Apollo moon landing took place in 1972 after a total of 12 astronauts landed on the lunar surface.
Astronaut Edwin ‘Buzz’ Aldrin unpacks experiments from the lunar module on the moon during the Apollo 11 mission. Photographed by Neil Armstrong, July 20, 1969