Theory 015/Earth & Space /Planetary surfaces
Lunar Swirls Are Magnetic Umbrellas
Swirls are bright markings with no topography. They sit on magnetic anomalies, and the debate is about which process connects them.
Lunar swirls are produced by magnetic shielding of the surface from solar wind weathering rather than by electrostatic dust transport, so swirl brightness should map onto the magnetic anomaly boundary.
01The evidence
Lunar swirls are associated with crustal magnetic anomalies and show reduced space weathering in the shielded regions.
02The tension
Electrostatic dust models explain the albedo pattern but not the association with magnetic boundaries, while shielding models explain the association but must account for the sharp edges.
03The mechanism
A crustal field deflects the solar wind, reducing the flux of ions that darken regolith. The boundary of the shielded region is where the field is strong enough to stand off the wind, which produces a sharp edge in albedo.
That makes the swirl a map of the magnetic standoff surface, which can be predicted from the anomaly strength and the wind pressure.
04What this is not
Dust models make swirls a surface process. This makes them a plasma boundary, which predicts edges that follow field lines.
05Predictions
- P1Brightness should map onto the standoff boundary.
- P2Edges should be sharp where the field gradient is steep.
- P3Swirl contrast should vary with solar wind pressure.
06Refutation
Swirls that persist inside the standoff boundary with weathering comparable to outside would refute shielding.
07What it changes
It would make swirls a probe of ancient lunar fields.