Reiner Gamma magnetic anomaly

The central element of Reiner Gamma resembles the pattern of force field lines formed by iron filings on a surface with a magnet beneath it. Low-orbiting spacecraft have registered a comparatively strong magnetic field associated with each of these albedo features. Some have suggested that this magnetic field and these patterns formed from collisions with comets. However, the true cause remains uncertain.

The magnetic field strength of Reiner Gamma, measured at an altitude of 28 km, is about 15 nT. This is one of the strongest local magnetic anomalies on the Moon. The field strength of this structure at the surface is sufficient to form a minimagnetosphere extending 360 km across the surface, creating a region of enhanced plasma 300 km thick in which the solar wind flows around this field. Since solar wind particles are known to darken the lunar surface, the magnetic field in this area may be the reason for the preservation of this albedo feature.