For decades, scientists have known that the moon’s hazy dust halo sits unevenly around it — denser on the sunlit side than the dark side. A new study suggests that the extreme fluctuations in the Moon’s day-night temperature are responsible for this. Using computer models, the team found that daytime meteor impacts blow about 6-8% more dust skyward than on cool nights, causing daytime dust to become thicker, causing clouds to bend toward sunlight.

Heat and Oblique Halo According to the new study, the team simulated micrometeoroid strikes on warm-day soil versus cool-night soil. Daytime impacts resulted in 6–8% more dust and more particles flying into orbit.

“The ejected dust particles are tracked individually to monitor their distribution in space,” explains Sébastien Verkerke, a postdoctoral researcher at the Center National d’Etudes Spatiales (France’s national space agency) in Paris and first author of the new study, “which means that the afternoon blow throws additional dust up. ” NASA warns that moon dust “can damage everything from lunar landers to spacesuits and human lungs if it is inhaled”, highlighting why tracking dust matters for space missions. Even Mercury’s large day-night fluctuations should increase this asymmetry – ESA’s BepiColombo probe may soon test this.

Meteorite Origin of Moon Dust Micrometeoroids constantly hit the Moon’s surface, turning rocks into dust. Each small blow sends the grain up, creating a weak halo.

In 2015, NASA’s LADEE orbiter confirmed a dust halo hundreds of miles above the Moon. Mihaly Horany, a physicist at CU Boulder, says that “a single dust particle from a comet hitting the lunar surface releases thousands of smaller dust particles into the airless atmosphere”, adding that regular impacts maintain the haze.

What is interesting is that the cloud is asymmetric – it becomes denser on the sunlit side closer to dawn.