New research suggests the moon is permanently surrounded by a giant lopsided dust cloud that gets denser during events such as the Geminids meteor shower.
The cloud is composed of dust grains from the moon's surface that are shot into space from the impact of high-speed, interplanetary dust particles, the University of Colorado at Boulder reported. A single dust particle from a comet striking the moon could send thousands of others into space, creating a cloud around the moon.
The cloud was discovered using g data from NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE). The first hints of the dust cloud were spotted in the late 1960s when NASA cameras aboard unmanned moon landers noticed an unusual glow above the lunar surface during sunrise. Years later, Apollo astronauts orbiting the moon noticed the same eerie glow.
"Identifying this permanent dust cloud engulfing the moon was a nice gift from this mission," said CU-Boulder physics Professor Mihaly Horanyi, the principal investigator on LDEX and lead study author. "We can carry these findings over to studies of other airless planetary objects like the moons of other planets and asteroids."
The new findings do not completely line up with what was observed during the early Apollo missions, suggesting the conditions of the cloud may have changed to become thinner and lower hanging. The Geminid meteor showers occur each December when the Earth moves through a cloud of debris from the Phaethon, which has been referred to as a "cross between an asteroid and a comet."
"When these 'beams' we see from meteors at night hit the moon at the right time and place, we see the cloud density above the moon skyrocket for a few days," Horanyi said.
The findings could help astronauts of future space missions avoid potential hazards, such as damage to spacecrafts and suits imposed by dust particles.
The findings were published in a recent edition of the journal Nature.
