Localized bubbles of high magnetic intensity may explain some enigmatic lunar surface features
Swirls in Mare Ingenii, far side of the Moon
The Moon, unlike Earth, has no global magnetic field but many surface locales of limited extent (tens of kilometers across) are magnetized. In many instances, these small areas of high magnetic intensity are associated with unusual patterns of surface brightness (albedo, or degree of reflectance) that occur in curved, blotchy or other strange “swirl-like” shapes. First observed by telescope, lunar scientists have been puzzled by the possible origin of what they imaginatively named “swirls.”
An example of a lunar swirl is a feature named Reiner γ (pronounced “Reiner gamma”), a bright splotch in southern Oceanus Procellarum, the dark mare region of the western near side. The name indicates that initially this feature was thought to be an isolated peak of highland material that juts up through the mare (lowercase Greek letters were assigned to such prominences in the old nomenclature.) However, even at very low sun elevations, close examination shows that this bright patch does not cast a shadow. It is simply a bright patch on the surface, one with diffuse and nebulous edges, yet clearly more reflective ...