Pale brushstrokes across the Moon
Processed image. Wide Angle Camera mosaic showing Reiner Gamma’s bright loops across the lunar plain. Mosaic seams and the published 100-kilometre scale bar are retained. Compare it with the narrower NAC mosaics, whose illumination and coverage differ.
NASA/JPL image-use policy · credited mission imagery, resized to WebP
· Original image source · Image licenceLunar swirls have striking outlines without matching mountain ranges.
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- Images & research · 2010–2022
Look closer
Reiner Gamma and Mare Ingenii carry bright, looping patterns across the lunar surface. Their relationship with magnetic anomalies has made them a long-running puzzle about surface weathering.
Follow the evidence
The photographs and regional views show more than one swirl locality. Compare the brightness patterns with craters and terrain, looking for places where a swirl crosses an existing landform.
Testing the magnetic sunscreen idea
Jan Deca’s team modelled both ions and electrons moving through magnetic fields constrained by Kaguya and Lunar Prospector measurements. Their simulation reproduced Reiner Gamma’s broad brightness pattern and agreed qualitatively with observations of reflected solar-wind protons. Deflecting charged particles could slow the weathering that darkens lunar soil. This is agreement between a physical model and observations, rather than a photograph of shielding in action or a complete explanation of every swirl.
A pattern still permits competing histories
NASA’s synthesis distinguishes magnetic shielding from other proposed mechanisms: comet-impact material could alter both brightness and magnetism, or magnetic and electric forces could sort fine grains. Bright swirl regions appear less weathered, yet not every magnetic anomaly carries a swirl. John Keller noted that ultraviolet observations support shielding without excluding alternatives. The visible pattern and its magnetic association constrain explanations; they do not by themselves identify the original magnetizing event.
Sources & further reading
- Lunar Swirl Reiner Gamma — NASA Image and Video Library / GSFC
- Lunar Swirls at the Mare Ingenii — NASA Image and Video Library / JPL
- Lunar Swirl Features Reproduced by Modeling Solar Wind Standoff — NASA / IMPACT, University of Colorado; Jan Deca and colleagues
- NASA Research Gives New Insights into How the Moon Got Inked — NASA Goddard / DREAM-2; William Steigerwald
- Reiner Gamma · high Sun — controlled NAC mosaic archive record — LROC / NASA Planetary Data System
- Reiner Gamma · low Sun — controlled NAC mosaic archive record — LROC / NASA Planetary Data System
- Controlled LROC Narrow Angle Camera High Resolution Mosaics — Klem and colleagues (2014) — 45th Lunar and Planetary Science Conference / LROC archive citation