A passage on lunar swirls is shown below, followed by three hypotheses. Match each hypothesis to the statement that best describes its stance on the origin of the magnetic anomalies and the cause of the brightness contrast.
### Lunar Swirls
Lunar swirls are light-colored, winding patterns observed on the Moon's surface. They are always associated with localized crustal magnetic fields (magnetic anomalies), but their origin is debated.
Hypothesis 1 (Comet Impact)
Lunar swirls are created when a comet coma collides with the lunar surface. The gas and dust in the coma mechanically scour away the dark, weathered upper layer of lunar soil (regolith), exposing the brighter, unweathered soil underneath. The impact's high-energy plasma flow magnetizes the local iron-bearing minerals in the crust, forming the magnetic anomaly. This event occurs instantaneously, and the swirls are stable features that do not change over short timescales. Solar wind weathering does not play a significant role in creating the brightness contrast.
Hypothesis 2 (Solar Wind Shielding)
Lunar swirls are the result of ongoing shielding from solar wind weathering. Solar radiation and ions normally darken the lunar surface over millions of years. However, the localized crustal magnetic anomalies—which are remnants of an ancient, now-defunct global lunar dynamo—deflect the solar wind. The shielded areas remain bright, while unshielded areas surrounding them continue to darken. Swirl formation is a slow, gradual process, and the swirls are not currently undergoing active surface transport or dynamic changes.
Hypothesis 3 (Dust Transport)
Lunar swirls are formed by the electrostatic transport of fine dust. The Moon's surface is electrically charged by solar ultraviolet light. Near crustal magnetic anomalies (remnants of an ancient global magnetic field), localized electric fields are created. These electric fields selectively loft and transport very fine, highly reflective dust particles, concentrating them along the magnetic field lines. This electrostatic sorting is an active, dynamic process occurring daily, meaning the swirl patterns are constantly refreshed and can change over short periods. Solar wind shielding is not the main cause of the brightness contrast.
- Hypothesis 1 (Comet Impact)Claims that the magnetic anomaly is created instantaneously by plasma flow during an impact, and that solar wind weathering is not responsible for the brightness contrast.
- Hypothesis 2 (Solar Wind Shielding)Claims that the magnetic anomaly is an ancient remnant that shields the surface, slowly preventing solar wind from darkening the area over millions of years.
- Hypothesis 3 (Dust Transport)Claims that the magnetic anomaly is an ancient remnant that enables localized electric fields to dynamically transport and sort bright dust particles daily.