Imma Perfetto
Cosmos science journalist
In fascinating research, which might change our understanding of the moon, scientists in the US have estimated a new timespan for when the Moon’s magnetic field could have existed, if it ever did.
The analysis of lunar rocks collected from the Apollo missions suggests that, if a magnetic field did once exist on the Moon, it had to have been during its first 140 million years.
A paper describing the work has been published in the Nature journal Communications Earth & Environment.
Earth’s powerful magnetic field, which shields us from solar wind, is generated by the churning of liquid iron in the planet’s core.
The Moon has no such magnetic field and scientists have struggled since the 1980s to determine whether it once did.
Some models, based on analysis of whole rock samples collected during the Apollo 16 and Apollo 17 missions, assume it possessed one as strong as Earth’s for nearly 2 billion years.
But other calculations suggest the Moon’s core is too small, and would have cooled down too quickly, to sustain a field of this strength.
In this new study, researchers used a technique known as single crystal paleointensity (SCP) to analyse 4 samples, formed between 3.69 and 4.36 billion years ago.
SCP works by analysing single silicate crystals that contain magnetic iron particles, which record information about the strength of the magnetic field when they formed.
The analysis showed that no Moon-wide magnetic field existed at the time of their formation, meaning such a field could only have existed before 4.36 billion years ago.
Although the exact age of the Moon is still debated, their best estimate is that the Moon’s magnetic field may have existed for about 140 million years at most (between 4.36 billion years ago and the Earth’s formation approximately 4.5 billion years ago).
The lack of a protective magnetic field for much of the Moon’s history could mean traces of Earth’s atmosphere, dating back to as much as 4.36 billion years ago during the Hadean eon, are buried in lunar soil.
“As the Moon passes through Earth’s magnetic field, elements from Earth’s atmosphere can be deposited on the lunar surface, and these may hold clues about the earliest Earth,” writes corresponding author John Tarduno of the University of Rochester, USA, in an article in The Conversation.
