Absence of a long-lived lunar paleomagnetosphere

Area of Science:

• Planetary Science
• Geophysics
• Lunar Science

Background:

• Understanding the Moon's magnetic field history is key to its evolution.
• The presence or absence of a long-lived lunar magnetic field has significant implications for lunar interior and surface processes.

Purpose of the Study:

• To determine if the Moon possessed a long-lived magnetic field.
• To investigate the origin of magnetization in lunar samples.
• To assess the implications for the Moon's paleomagnetosphere and resource preservation.

Main Methods:

• Analysis of impact glass from a young lunar crater.
• Magnetization studies on silicate crystals from Apollo samples of various ages (∼3.9 to 3.2 billion years ago).

Main Results:

• Apollo impact glass records a strong, Earth-like magnetization, indicating impacts can create intense magnetic signals.
• Ancient silicate crystals (∼3.9, 3.6, 3.3, and 3.2 billion years ago) show capacity for recording strong fields but do not exhibit such magnetization.
• These findings collectively suggest the Moon lacked a sustained core dynamo.

Conclusions:

• The Moon did not possess a long-lived core dynamo.
• Absence of a sustained paleomagnetosphere means the Moon was exposed to solar winds and Earth's magnetosphere for billions of years.
• Lunar regolith likely contains significant buried resources like helium-3, water, and other volatiles accumulated over time.