The Mystery of the Moon's Core: Solid or Liquid?

The moon has long fascinated scientists and researchers due to its enigmatic and mysterious nature. One of the most intriguing questions revolves around the core of the moon. Is it solid or liquid, and what makes it so elusive?

Ancient Science and Modern Answers

For years, the composition of the moon's core has been a topic of intense debate. The iron element, always found in conjunction with nickel, is well-known on Earth. However, the lunar core also contains an abundance of cobalt and copper due to the S-process in certain stars. Understanding the makeup of the lunar core can shed light on the moon's formation and evolution.

Currently, the prevailing model suggests a solid metal core surrounded by a liquid metal core, similar to the structure of the Earth. Despite this model, the true nature of the moon's core remains a subject of discussion. Some theories propose that the moon might have a tiny, molten, compressed core, but the energy required for this would have long ago dissipated due to the moon's smaller size and tidal forces.

Advancements in Lunar Core Analysis

Recent advancements in technology and data processing have provided some clarity on the structure of the moon's core. In 2010, a reanalysis of Apollo seismic data on deep moonquakes confirmed that the moon has an iron-rich core with a radius of approximately 330 ± 20 km. This analysis also revealed that the solid inner core, made primarily of iron, has a radius of about 240 ± 10 km. Surrounding this core is a partially melted layer of the lower mantle, with a radius of 480 ± 20 km and a thickness of approximately 150 km.

These findings suggest that about 40% of the core by volume has solidified. The density of the liquid outer core is estimated to be around 5 g/cm3, and it could contain up to 6% sulfur by weight. The temperature in the core is thought to range between 1600 to 1700 K. These details provide a clear picture of the moon's internal structure and help to answer some of the fundamental questions about its composition.

The Seismic Experiment of Apollo

The Apollo missions introduced a seismic experiment on the lunar surface to study the moon's core directly. The landing module was equipped with a seismometer, which recorded local moonquakes and impacts. After the lander jettisoned and fell back to the moon, it impacted the surface, and the seismometer on the lunar surface registered this impact. A short while later, the same impact was recorded once again, but this time the signal was weaker. This repetition of data collection provided scientists with valuable insights into the moon's internal structure.

The early theory suggested that the moon's core could either be hollow or solid. While a hollow core is difficult to support due to general geological reasons, the solid core is considered the more likely answer. The seismic data collected during the Apollo missions provided supporting evidence for the solidity of the moon's core, aligning with the reanalysis conducted in 2010.

The mystery of the moon's core continues to intrigue scientists, but the advancements in technology and the reanalysis of Apollo data bring us closer to understanding this celestial body's internal composition.