The Swirl of Reiner Gamma
A bright, tadpole-shaped swirl lies painted on the dark plain of the Moon, with no hill, crater or cliff to explain it.
What was reported
Reiner Gamma is a bright marking about 70 km long on the Moon's Ocean of Storms, curling like a tadpole or a swirl of milk in coffee. It was drawn on maps of the Moon from the 17th century, but no telescope or spacecraft has found anything that rises above the ground there: it's a pattern on a flat surface.
Spacecraft found that it sits exactly where there's a strong local magnetic field, something the Moon mostly lacks.
Explanations offered
The leading idea is that the magnetic field deflects the solar wind, which elsewhere slowly darkens the Moon's surface, leaving this patch bright. But what makes the magnetism is still debated: buried magnetised rock, the remains of a comet impact, or something else. NASA has planned a small lander to study it.
- When
- Charted since the 1600s
- Where
- Reiner Gamma, Ocean of Storms, the Moon
- Witnesses
- Astronomers and lunar spacecraft
- Status
- Unexplained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.