Indigenous noble gases in the Moon's interior

Area of Science:

• Lunar and Planetary Science
• Geochemistry
• Noble Gas Geochemistry

Background:

• The origin of lunar volatiles remains a significant debate in planetary science.
• Proposed scenarios include inheritance from the Moon-forming disk, late accretion via meteorites or comets, or solar wind implantation.
• Noble gases serve as critical tracers for understanding volatile origins due to their inert nature and distinct isotopic signatures.

Purpose of the Study:

• To investigate the origin of indigenous noble gases within the Moon's interior.
• To differentiate between various volatile delivery mechanisms to the Moon.
• To constrain the Moon-forming impact scenario and volatile storage reservoirs.

Main Methods:

• Analysis of all noble gases (He, Ne, Ar, Kr, Xe) in paired, unbrecciated lunar mare basalt samples.
• Petrological examination of magmatic glasses and minerals to establish sample context and rule out contamination.
• Isotopic analysis to identify solar-type, chondritic, or terrestrial signatures.

Main Results:

• Indigenous noble gases, including solar-type Helium (He) and Neon (Ne), were identified within magmatic glasses of lunar mare basalts.
• Evidence excludes assimilation of solar wind-bearing regolith or direct solar wind implantation into the basalts.
• Absence of chondritic primordial He and Ne signatures rules out exogenous contamination from meteorites or comets.

Conclusions:

• The Moon inherited indigenous noble gases directly from Earth's mantle during the Moon-forming impact event.
• These primordial volatiles are likely stored within the potassium, rare earth element, and phosphorus (KREEP) enriched reservoir in the lunar interior.