Lunar Swirl Features Reproduced by Modeling Solar Wind Standoff

Exoplanet, wind

The first 3D simulations were created by a group of researchers at the Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT) at the University of Colorado; this device can disentangle ions and electrons movements as the solar and the lunar magnetic anomalies interact. The researchers made use of NASA’s Pleiades supercomputer, along with observations from lunar satellite to demonstrate how solar wind standoff can reproduce lunar swirl features.

Lunar swirls are enigmatic features found on the surface of the Moon characterized by bright pattern or streaks in the lunar soil that is much brighter than the regolith surrounding it. All lunar swirls are found where crustal magnetic anomalies have been detected. However, the swirly markings are not found in all magnetic anomalies; thus, lunar swirls have become an interesting puzzle yet to be answered. Ever since the Apollo era, there have been debates on what could be the possible cause of lunar swirls. There is a possibility that fresh impacts by micrometeoroids and comets might have deposited fine, unweathered substances with remnant magnetization that made the surface bright naturally, or maybe the presence of lunar magnetic anomalies inhibited weathering by solar wind ions and the regolith darkened due to production of nanophase, or electro-statistically levitated dust experienced a type of magnetic sorting.

The Reiner Gamma crater has a lunar swirl co-located with one of the Moon’s strongest crustal magnetic anomalies. This might create a mini-magnetosphere that prevents the solar wind plasma from forming brighter areas on the lunar surface while focusing plasma into the darker areas. The researchers were able to recognize that if the weathering pattern of the surface formed by the solar wind corresponds with the observed albedo markings, it will back the idea that lunar swirls are created by solar wind standoff.

The researches made use of a complete kinetic code that resolves both the electron and ion dynamics. Using Kaguya and Lunar Prospector magnetic field measurements, the researchers were able to implement a 3-dimensional geometry and topology of the lunar crustal magnetic field.

The researchers discovered that solar wind standoff reproduces the shape of the Reiner Gamma swirl pattern. Their technique also showed why not all magnetic anomaly creates a distinct albedo marking: the shape, size and direction of the electric field are essential elements that regulate proton energy flux to the surface. Solar wind standoff describes the correlation between the lunar magnetic anomalies and the lunar surface albedo patterns.

Previous research by Deca et al. focused on the interactions of the solar wind with dipolar magnetic fields and outgassing comets, but latest research has stretched out to the solar wind interactions with magnetic irregularities on the Moon’s surface.

The paper titled “Reiner Gamma albedo features reproduced by modeling solar wind standoff,” was published in the April 2018 issue of Nature’s Communications Physics. The NASA’s Solar System Exploration Research Virtual Institute (SSERVI) in Silicon Valley funded this research. The research was carried out by the Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT) – a SSERVI team at the University of Colorado in Boulder.