A lopsided cloud of dust permanently engulfs the moon, but until recently the cloud has largely remained a mystery to the scientific community. According to a new study from the University of Colorado at Boulder, however, we may be on the brink of cracking the case of the lunar dust cloud.

The cloud is mainly composed of small grains of dust that were brushed up from the moons surface as a result of high-speed impacts from small space particles. According to CU-Boulder physicist Mihaly Horanyi, when even a single dust particle from a comet strikes the moon, it sends thousands of smaller dust particles shooting up into the low-gravity and airless environment. The lunar dust cloud remains hovering above the moon’s surface year-round, though there is a seasonal variation as various comets orbit closer to the moon.

NASA’s Lunar Atmosphere and Dust Environment Explorer, LADEE, launched in 2013, helped pull back some of the mystery surrounding the moon’s dust cloud. The craft used a detector called the Lunar Dust Experiment, or LDEX, which charted over 140,000 impacts over the course of a six-month mission.

Horanyi said that the discovery of the dust cloud was a pleasant surprise of the mission. The findings can apply to other bodies in space that are in the path of small comet debris, and will be useful in understanding some of the risks involved with advanced space exploration.

The study appeared in the June 17 version of the journal, Nature.