The moon may never actually have had a strong magnetic field

The moon, despite being made from the same material as Earth's planet, may not have experienced a strong magnetic field similar to Earth's Michael Osadciw/U. RochesterNew analysis of lunar rocks collected by Apollo missions has revealed that the only natural satellite may not have had a strong magnet field as previously believed.It formed approximately 4.5 billion years ago from a collision that sent a portion of our planet out to orbit. The moon has an iron core similar to Earths. Although the moon's current magnetic field is only one-thousandth of the strength of Earths, initial analysis in 1970s moon rocks suggested that it was as strong as Earths between 3.9 billion and 3.6 billion years ago. It was assumed that the field had long since vanished.John Tarduno, University of Rochester in New York, says it was a surprise to discover evidence of a strong magnet field in rocks after the Apollo missions. This is because the moon was not large enough to provide sufficient power. He says that no one has been able solve this paradox. What good is a magnetic field without a way to power it? You didn't have a magnetic fields.AdvertisementHis colleagues and he believe that this strong field is due to the magnetization of moon rocks by the shocks of asteroid impacts. The team found no evidence of such a field in other Apollo-era rocks samples taken from different lunar locations.Researchers analysed a glass-like piece of moon rock formed by an asteroid collision 2 million years ago and discovered evidence of a strong magnet field. This magnetic field was evident when the rock cooled and solidified. However, by this time the moon's magnetic field had weakened. This indicates that the impact caused magnetisation. However, older samples could also be affected by the same effect. Previous researchers incorrectly concluded that the moon was active in its magnetic field.The team also examined samples that date back to between 3.9 billion and 3.2 trillion years ago and found no evidence for a strong magnetic field. If such a field were present, the samples would have contained minerals that could have recorded it during cooling and formation.Tarduno claims that these results together prove that the moon did not have a strong, long-lasting magnetic field. Tarduno admits that the moon may have had a magnetic field for the first 100million years after it was formed. However, this is before the moon cooled down and stabilized. As the landscape is continually pummelled by asteroid impacts, there are no rocks that date back to this time.Tarduno says that if we were able to find such rocks and drill down, maybe as part NASAs upcoming Artemis program, it could give insight into Earth's early composition. This is because the moon would have passed through the magnetic field of Earth and picked up trace materials. If the moon had strong magnetic fields, such an experiment would not be possible.Journal reference: Science Advances, DOI: 10.1126/sciadv.abi7647Subscribe to the Launchpad newsletter and take a journey across the galaxy every Friday!