The moon’s magnetic field disappeared a BILLION years ago after the “internal dynamo” stopped
The once strong protective magnetic field of the moon disappeared about a billion years ago when its internal dynamo stopped working, a study found.
To determine the strength of the field in the past, researchers studied rocks on the moon’s surface that were formed from melt generated by a large impact.
As this rock cooled, small grains entered in line with the magnetic field to form a snapshot of the strength and direction of the field at that time.
Researchers discovered that the field had fallen to 0.1 microteslas a billion years ago – about 500 times weaker than today’s earth’s surface.
This, she added, suggests that the dynamo driving the field – driven by the crystallization of matter in the lunar core – had stopped by that time.
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The once strong protective magnetic field of the moon disappeared about a billion years ago when its internal dynamo (shown in this cutaway) stopped working, a study has shown
WHAT HAS THE MOON CAUSED?
The impression of an artist that Theia touches the earth
The moon of the earth would have formed around 4.5 billion years ago.
It was created in the aftermath of a collision between the young earth and a body the size of Mars.
Researchers have called this giant impactor ‘Theia’.
The rubble that was thrown into orbit by the collision eventually merged under gravity to form the moon.
The giant impact hypothesis
Essential in protecting us from the stream of charged particles that are emitted from the sun, the magnetic field of the Earth is the product of the electrical currents that are generated as liquid metal circulates in the core of our planet.
The moon used to have a robust magnetic field – but that has not disappeared for a long time.
“A strong field on the moon may have protected the surface against the solar wind, the supersonic plasma emitted by the sun,” said planetary scientist Benjamin Weiss of the Massachusetts Institute of Technology Newsweek.
“This may have prevented the surface from weathering the space and the soil becoming rich in solar gases, as is the case now,” he added.
“Moreover, the moon was probably about twice as close to the earth during the time that the moon was distracted to have a strong magnetic field compared [with] today.’
The moon is still drifting slowly away from us, at a speed of about 1 inch (2.5 cm) per year.
In their previous research, Professor Weiss and colleagues revealed that the moon’s magnetic field was about 100 microteslas four billion years ago – or about twice the strength of the Earth’s magnetic field today.
The team determined this by analyzing lunar rock samples formed by lunar volcanic activity.
As this erupting material cooled and solidified, the small grains would do it to align the rocks in the direction of the moon’s magnetic field – capture a snapshot of its strength and direction as small frozen compasses.
This method for measuring the past magnetic field of the moon has its limitations – where researchers rely on the continued formation of molten rock to keep the record going.
About three billion years ago, however, volcanic activity on the moon had largely stopped.
“The past three billion years of lunar history has been a mystery because there is almost no rock report,” Weiss told Newsweek.
To determine the strength of the field in the past, researchers studied rocks on the lunar surface formed from melt generated by a large impact
However, volcanoes are not the only way molten rock can be formed on the moon – some melt can be formed when bodies collide with the moon surface.
In 2017, the team found rocks formed in such an impact 2.5 billion years ago – their analysis showed that the moon’s magnetic field had dropped to around 10 microtesla at that time.
In their latest study, Professor Weiss reports that he found similar rocks that were formed after a major impact about a billion years ago – revealing that the magnetic field was no stronger than 0.1 microteslas at the time.
According to the researchers, this suggests that the moon’s internal dynamo that powered the magnetic field was turned off by that time.
Researchers discovered that the field had fallen to 0.1 microteslas a billion years ago – about 500 times weaker than today’s earth’s surface. Depicted the total magnetic field strength on the surface of the moon as recorded by NASA’s Lunar Prospector in November 2006
The team believes that the magnetic field may have been driven by two different processes.
Initially, the proximity of the moon to the earth led to the gravity of the liquid in the core of the moon, creating the dynamo effect that drove the field.
As the distance between the earth and the moon increased, a second process – called “nuclear crystallization” – probably became more important.
Herein, the gradual formation of the dense iron inner core of the moon has fueled the surrounding fluid in the outer core and generated the magnetic field.
However, if the inner core had fully crystallized out of the outer core, this dynamo would have stopped functioning – although it is currently unclear whether it happened abruptly or flickered and on and off before it died completely.
“The magnetic field is this vague thing that permeates space, like an invisible force field,” said Professor Weiss.
“We have shown that the dynamo that produced the magnetic field of the moon died somewhere between 1.5 and a billion years ago.”
The researchers were allegedly assisted that the lunar dynamo will last for at least two billion years.
“This is because the moon is a small planetary body, so it cools down much faster than planets,” he said.
“Mars has a diameter about twice as large as that of the moon, and yet it is generally thought that the Mars dynamo ended before four billion years ago.”
“The moon’s dynamo must have had an unusually long-lived power source.”
WHEN WILL NASA RETURN TO THE MOON?
In a statement in March, NASA administrator Jim Bridenstine doubled plans to send people first to the moon and then to Mars and said: NASA is on its way to get people back on the moon by 2028.
The plan is based on the evolving Space Launch System and the Orion spacecraft, together with the orbital platform of Gateway.
SLS and Orion are expected to be ready for their first non-bolted test flight in 2020.
Construction on Gateway – an orbit around the moon – starts in 2022.
“We will be going to the moon in the next decade with innovative new technologies and systems to explore more locations on the moon surface than ever before,” said Bridenstine.
“When we go to the moon this time, we stay.
“We will use what we learn as we advance to the moon to make the next giant leap – sending astronauts to Mars.”
Vice President Mike Pence, however, tore these plans and statements when he unexpectedly unveiled a new deadline in March in which he intended to put people on the moon by 2024 – four years earlier.
The VP called on NASA to ‘re-ignite the spark of urgency’ for space exploration and to make it a priority to set ‘daring goals’ and stay on schedule.
NASA administrator Jim Bridenstine added a week later, early April, that the agency would be “very close” to delivering a plan by April 15.
This has been missed for several weeks and the House Science Committee is now expressing its dissatisfaction about the lack of a feasible plan or program from the space agency.
Now that their first study has been completed, the researchers now want to go further than just measuring the strength of the moon’s magnetic field.
“We are now trying to see if we can measure the direction of the old field with the help of Apollo samples from which we can construct the original orientations,” Professor Weiss told Newsweek.
The full findings of the study were published in the journal Science is progressing.