Archive

By Roman Ragazzo
October 24, 2025

Introduction

Our Moon, like many other places in the universe, is quite a dusty place. Over the course of its roughly 4.5 billion years of coexistence with Earth, it has not enjoyed the same privileges of a strong solar wind-deterring magnetic field, and thick atmosphere to conveniently burn up micrometeors and cosmic rays. Moon dust as a result is sharp, charged, and primed for electrostatic lofting.

Lunar Dust

Due to space’s harsh environmental conditions, mostly the likes of micrometeor impacts and high energy ionizing particles, lunar regolith has some rather interesting properties compared to the dust we are used to on Earth. Us Earth observers are used to weathered, rounded, mostly electrically neutral dust grains made up from the same material as the Earth’s crust. On the moon, dust grains are created at high pressures and temperatures by micrometeorites and ionized by the solar wind and cosmic rays. They are notably not eroded once they are formed, as there is obviously no air or water present to weather them over time, as is the case on Earth. 

The side effects of these formation conditions are small, sharp dust grains that carry a heavy charge and mechanically stick to each other, as well as everything else. The net regolith charge also changes with location. High energy solar radiation strips electrons, causing dust grains on the day-side of the moon’s surface to carry a net positive charge. Near the terminator and on the night side, solar wind electrons slowly collect and give the surface a net negative charge [1]. 

Electrostatic Lofting

Solar wind electrons ending up on the night-side may seem counterintuitive from a classical physics perspective, specifically the context of drag and wake forces. The mechanics of how this can happen regardless is itself an incredibly interesting topic. However, this electric charge and subsequent surface electric field gives rise to a very interesting physical phenomenon and the main subject of this blog post: electrostatic lofting.

Electrostatic lofting occurs when surface trapped dust grains become dislodged from the lunar surface, usually by impacts or the present surface electric field. Under natural circumstances, this is theorized to happen a lot at the terminator (the lunar day-night boundary), as the positive day side and negative night side combine for potential differences of up to hundreds of volts and complicated, dynamic electric fields over the region [1]. This voltage can be enough to launch (loft) small grains off of the surface. 

A common theoretical model to approximate this effect is the dynamic fountain model. In this model, grains are accelerated to a high initial velocity in the region directly above the lunar surface (~0.1 - 10m, depending on the distance from the terminator) before following a parabolic ballistic trajectory [4]. Under this model, grains can reach high lunar altitudes depending on their net charge and mass. LADEE/LDEX observations imply charges in the range of femtocoulombs (0.1~10 fC) [2], however this can only be inferred with detector charge transfers. That said, smaller grains (~0.1-1μm) are simulated to reach altitudes up to 100 km in this model [4].

Observations do generally align with the existence of high altitude dust grains in the lunar exosphere. LADEE/LDEX mission data does support the permanent presence of dust grains at high altitudes, and higher densities near the terminator were observed [2]. Apollo astronauts also reported the presence of a ‘horizon glow’ at lunar sunrise, theorized to be caused by light scattering due to these dust clouds [5], however the inferred densities from these sets of observations are not particularly in agreement [2;5].

Human Activity & A Note of Importance

The disturbance of dust grains on the surface by human activity becomes a fruitful discussion in light of this phenomenon. The most popular potential destinations for a permanent human presence lie close to the moon’s poles, regions which are always very close to the lunar terminator. This fact, combined with models of electrostatic lofting and observations of dust exospheres before the consistent presence of humans hint that dust clouds may become much more pronounced if extensive activity from people, rovers, and other instruments exist. It’s easy to infer how this may cause problems with dust contamination on lunar equipment over long timescales. Additionally, it has already been theorized that the current levels of exospheric dust may cause some amount of scattering for astronomical observations in the infrared, visible, and ultraviolet [3]. This may become exacerbated with heavy disturbance of regolith on the lunar surface. It becomes quite important to consider some serious dust management precautions if one wishes to keep these effects to a minimum. Ultimately, understanding and mitigating the behavior of lunar dust will be essential to ensuring the longevity and success of sustained human and scientific activity on the Moon.

By: Jonathan Durkin
October 13, 2025