Moon once had a magnetic core, which helped it to generate a magnetic field similar to Earth. Now, researchers believe that there has no dipolar magnetic field exist on Moon which can be generated from the lunar core.
However, NASA's latest study explained that around 3 billion years ago Moon had an active magnetic field. They informed that the heat from crystallization of the lunar core powered that now-defunct field.
During the Apollo's lunar mission astronauts returned to Earth with some Magnetized lunar rocks. From that, scientist understood about the existence of the magnetic field in the ancient lunar surface. Though, the previous study never answered about the generation and stability of the magnetic field in the early stage of Moon. However, recent analysis suggests that a molten, churning lunar core at the center of the moon stabilized the magnetic field.
This mechanism of lunar core is called lunar dynamo. According to dynamo theory, it describes the mechanism through which a rotating, electrically conducting fluid can maintain a magnetic field. However, this lunar magnetic field lasted for more than a billion years.
Regarding a paper recently published in ScienceDirect, the moon likely had an iron or nickel core. Besides, they found the presence of small amount of sulfur and carbon that increase the melting point of the lunar core. Eventually, it resulted in the acceleration of crystallizing of the lunar core in the early stage in lunar history.
According to studies on lunar samples, the heat released from crystallization procedure may have driven an early magnetic field. For the study, researchers at Astromaterials Research and Exploration Science created several synthetic lunar cores from latest geochemical data compositions.
In this process, scientists prepared powders of iron, nickel, sulfur and carbon. These powders are prepared with estimated geochemical proportion from Apollo sample. Therefore powders were encapsulated and heated under pressures similar to the interior of the lunar core.
Furthermore, a magnetic field has been recorded in lunar samples as young as 3.1 billion years old. Regarding Apollo seismic data, the lunar core is thought to be composed of a solid inner and liquid outer core. However, ARES group proposed a new lunar core composition which would likely be partially solid and liquid.
