A peculiar and uneven dust cloud surrounds the Moon, always leaning toward the side that’s lit by the Sun. Recent research has shed light on why this cloud takes its strange shape.
The Moon’s surface is covered with regolith, a mix of fine dust and loose rocks. This regolith forms mainly due to countless micrometeoroids—tiny rocks from space hitting the lunar surface every day. Unlike Earth, where an atmosphere burns up these rocks before they reach the ground, the Moon experiences hits from tons of micrometeoroids daily, grinding the rocks into dust.
In 2015, scientists discovered that this dust creates a significant cloud hovering hundreds of miles above the Moon. Although it’s not visible from Earth, it’s important and intriguing. “The cloud’s maximum density was measured at just 0.004 particles per cubic meter,” said Sébastien Verkercke, a researcher at France’s national space agency. For context, this is like having only four grains of dust in a grain silo.
What’s particularly interesting is that this cloud is denser on the daytime side of the Moon than on the night side. The hottest temperatures on the Moon can reach over 250 degrees Fahrenheit during the day. In contrast, nighttime temperatures drop to levels colder than Antarctica, where it can get as low as -297 degrees Fahrenheit. This vast temperature difference (up to 545 degrees Fahrenheit) made Verkercke and his team wonder if this factor contributes to the cloud’s unevenness.
The researchers used computer models to test their idea. They simulated meteoroids hitting lunar dust at both extreme temperatures. They found that the warmer daytime impacts created 6% to 8% more dust than those during the cold night. Higher daytime temperatures may boost the energy of dust particles, allowing more of them to escape into space.
Their study also revealed that if the lunar surface is “fluffier,” it creates less dust when hit. This suggests that the dust clouds could help scientists understand how compact or loose the Moon’s surface is.
This research is leading scientists to explore how other celestial bodies react to micrometeoroids. Take Mercury, for instance. It’s much hotter than the Moon during the day, which could result in an even more asymmetric dust cloud. The upcoming BepiColombo mission aims to study this further, looking into how temperature differences affect dust on Mercury compared to the Moon.
This research highlights not only the dynamic nature of the Moon but also the intricate relationships between celestial bodies and their environments. The Moon, despite its silence, is, in fact, quite active when we think about these dust clouds and their implications for our understanding of the solar system. For further reading, you can check out the published study in the Journal of Geophysical Research: Planets.
